Physics doi: 10.3390/physics8020045

Authors: J. Va’vra

This paper examines whether a compact electron–proton configuration (“small hydrogen”) with a characteristic radius of a few femtometers is excluded by basic relativistic kinematics and simple stationarity constraints. Motivated by earlier discussions of formally deep relativistic energy scales in Dirac-based treatments, a phenomenological, virial-inspired energy-balance framework that incorporates relativistic kinetic energy, finite-size regularization of the central field, and order-of-magnitude spin–magnetic and spin–orbit contributions is developed in this paper. Within this framework, self-consistent characteristic scales associated is obtained with a hypothetical compact configuration without invoking Dirac or quantum-electrodynamics (QED) bound-state eigenvalues. The resulting scales—namely, a central energy scale of about 260 keV and a characteristic spin-dependent scale of order ΔEspin ≈ 100 ± 20 keV—define concrete experimental and observational energy ranges of interest. The present study does not establish the existence, formation probability, lifetime, or dynamical stability of such states. Rather, it shows that relativistic kinematics, finite-size effects, and virial-inspired stationarity constraints do not, by themselves, rule out compact stationary electron–proton configurations within the assumptions of the model. If such states were realized in nature and possessed radiative or interaction channels, those states may have implications for astrophysics, fusion concepts, and dark-matter phenomenology.

Physics doi: 10.3390/physics8020044

Authors: Diana Deară Oana Ristea Cătălin Ristea Alexandru Jipa

We present a study of the mean transverse momentum pT of identified strange hadrons (KS0,Λ,Λ¯,Ξ−,Ξ¯+,ϕ,Ω−,Ω¯+) produced in Au+Au collisions at RHIC-BES energies (the nucleon–nucleon center-of-mass energy sNN=7.7 GeV,11.5 GeV,19.6 GeV,27 GeV and 39 GeV). The mean transverse momentum is obtained from transverse momentum spectra of the strange hadrons as measured by the STAR experiment and its dependence on the number of participants Npart is studied. For RHIC-BES energies, experimental data indicate a centrality dependence of pT, with an increase towards central collisions. This dependency is described using a power-law function to fit the data. The power-law exponent α is used to characterize the degree of flattening of pT with respect to Npart and its dependency on the collision energy and particle mass is studied. Special emphasis is placed on ϕ-meson that has a smaller interaction cross-section, thus reflecting the properties of the early stages of the system’s evolution. The pT of ϕ-mesons produced in Au+Au collisions at RHIC-BES energies are compared with the results obtained in Au+Au collisions at higher RHIC energies and in Pb+Pb collisions at SPS and LHC energies. A distinct energy dependence of ϕpT values is identified. Furthermore, data indicate, when comparing peripheral and central heavy-ion collisions, that ϕ-meson pT increases with system size, following two distinct trends. The results are compared with the predictions of the default and string-melting versions of the AMPT generator. We observe that the string-melting AMPT version describes the strange meson pT, but underpredicts the strange baryon pT centrality dependence. The default AMPT overpredicts the KS0 and ϕ meson pT centrality dependence, while the strange baryon data are in general better described by this version of the model. The exponent α obtained from AMPT-simulated results does not describe the measurements satisfactorily.

Physics doi: 10.3390/physics8020043

Authors: Bing He Shengyu Peng Nan Sun Guoliang Li Xiaofei Zhu Peng Xu Xiaowei Shen

As a foundation for numerical solvers in computational electromagnetics, particularly for multiphysics and electromagnetic compatibility applications, Jefimenko’s equations offer a generalized solution to Maxwell’s equations, enabling the direct computation of electromagnetic fields from time-dependent source distributions without the boundary-condition artifacts inherent to grid-based methods. However, the numerical integration of these equations is computationally intensive, typically scaling as O(NsNo) for Ns source points and No observation points. In this paper, we present JefiFast, a highly optimized graphics processing unit (GPU) implementation that significantly outperforms the state-of-the-art JefiGPU algorithm. We identify that previous implementations are strictly memory-bound due to inefficient global memory transactions and a lack of data reuse. JefiFast addresses these bottlenecks through four key optimizations: (i) a packed memory layout (PML) using an array-of-structures approach to ensure coalesced memory access for source densities and their derivatives; (ii) geometry-aware shared memory tiling strategies that maximize L2 (level-2) cache hit rates and on-chip data reuse; (iii) pre-computation of time derivatives to minimize redundant arithmetic operations; and (iv) a robust observation domain decomposition strategy that enables linear scaling across multiple GPUs. Benchmarks demonstrate that JefiFast achieves speedups ranging from 4.08 times (for 303 grids on a single NVIDIA V100 graphic processor) to 84.51 times (for 503 grids on 4 NVIDIA V100 processors) compared to the baseline. Notably, for a 503 grid on a single GPU, JefiFast reduces execution time from about 51 min to just about 2.6 min (19.54 times speedup). These performance advances make high-resolution relativistic heavy-ion collision simulations feasible in near real-time.

Physics doi: 10.3390/physics8020042

Authors: Elmo Benedetto

General relativity is often perceived by undergraduate and advanced high-school students as conceptually and mathematically inaccessible. This paper does not provide new results in gravitation but rather introduces a lucid pedagogical framework for understanding gravitomagnetic effects in rotating systems. Starting from the Langevin metric, which describes flat spacetime in a uniformly rotating reference frame, the paper considers an apparent paradox: two clocks moving with identical velocities in an inertial frame but located at different radii on a rotating platform. While the equality of proper time of the clocks is expected in the inertial frame, its reconstruction in the rotating frame is not immediately transparent. It is shown here that this equality emerges from an exact compensation between three distinct contributions: a centrifugal potential term, a kinematic time dilation term, and a velocity-dependent term being formally analogous to a gravitomagnetic potential. The explicit identification and interpretation of these contributions constitute the pedagogical significance of this paper. Although the consideration presented is performed in flat spacetime, the formal analogy with gravitomagnetic effects provides students with an accessible pathway to more advanced concepts such as frame-dragging and the Sagnac effect, while highlighting the importance of velocity-dependent interactions in relativistic physics.

Physics doi: 10.3390/physics8020041

Authors: M. Shahbaz Ullah M. Javed Idrisi Sergey Ershkov

In this paper, the circular Sitnikov three-body problem is studied under the combined influence of radiation pressure and albedo. The model consists of two equal-mass primaries moving in circular orbits about their center of mass and an infinitesimal body constrained to oscillate along the perpendicular axis. The radiative emission from one primary and the reflected radiation from the other are incorporated into the effective potential through radiation and reflectivity parameters. Using the Jacobi integral, we determine the energetically admissible region for vertical motion and examine how radiative effects modify the accessible phase space. The study shows that the system admits a single vertical equilibrium point at the origin, which remains linearly stable within the physically admissible parameter range. Radiation and albedo reduce the effective restoring force and increase the oscillation period, producing a measurable rescaling of the physical time without altering the geometrical structure of the phase trajectories. The phase-space dynamics are further explored by means of Poincare (first-return) maps obtained from numerical integration of the nonlinear equation of motion. The resulting invariant curves confirm that the motion remains regular and bounded, while their progressive contraction reflects the reduction in the oscillation amplitude with increasing radiative effects. Overall, the results show that albedo acts as a quantitative modifier of the vertical Sitnikov dynamics by changing the effective potential, the admissible energy domain, and the observable time scale, without generating new qualitative phase-space structures.

Physics doi: 10.3390/physics8020040

Authors: Larissa Inácio Felipe S. S. Rosa Astrid Lambrecht Paulo A. Maia Neto Serge Reynaud

The Casimir interaction in salted water contains a universal contribution of electromagnetic fluctuations that makes it of a longer range than previously thought. The universal contribution dominates non-universal ones at the distances relevant for actin fibers inside the cell. We discuss universal and non-universal contributions with a model mimicking biological matter. We also show that the universal Casimir effect should have crucial implications at the cell scale.

Physics doi: 10.3390/physics8020039

Authors: Nikolay V. Sidorov Mikhail N. Palatnikov Alexander Y. Pyatyshev Alexander V. Skrabatun

It is found that the speckle structure of the photoinduced light scattering indicatrix of the LiNbO3:Y3+(0.46 wt%) crystal and its behavior with the time of crystal irradiation with a laser undergo an atypical behavior caused by the features of the dissipation processes of laser-induced defects in the crystal. In the frequency range of 100–4000 cm−1, the Raman spectra of the LiNbO3:Y3+(0.46 wt%) single crystal were recorded upon excitation by visible (532 nm) and near-IR (785 nm) laser radiation. Five second-order Raman scattering lines were detected in the frequency range of 1000–2100 cm−1, with the frequencies of two of them (of about 1790 cm−1 and 1940 cm−1) somewhat exceeding the doubled value of the frequencies of fundamental vibrations of the 4A1(z)LO (longitudinal optical) and 9E(x,y) symmetry types, which allows us to attribute these lines to the overtones of the fundamental vibrations of 4A1(z)LO and 9E(x,y). It is found that only one Raman scattering line is observed in the region of stretching vibrations of OH-groups (3200–3800 cm−1). The frequency of this line is found to depend on the scattering geometry, varied within 3431–3438 cm−1, and to be shifted to the low-frequency region by about 30–50 cm−1 relative to the frequencies in the IR absorption spectrum. This finding may be due to the alternative prohibition rule due to the presence of the center of symmetry of the oxygen octahedra O6 of the crystal structure.

Physics doi: 10.3390/physics8020038

Authors: Anatoly A. Gurchenkov Ivan A. Matveev

The evolution of the flow of a viscous, electrically conductive, incompressible fluid on a rotating wall in the presence of a magnetic field is studied. The wall forms an arbitrary angle with the axis of rotation. The unsteady flow is induced by longitudinal oscillations of the wall and a suddenly applied magnetic field directed normal to the wall. An analytical solution to the three-dimensional unsteady magnetohydrodynamic equations is presented for the case of infinitely high fluid conductivity. The velocity field and induced magnetic field in the flow of a viscous, electrically conductive fluid are determined. A number of special cases of wall motion are considered. Based on the obtained results, the influence of the magnetic field on the characteristics of the waves emitted by the wall is investigated.

Physics doi: 10.3390/physics8020037

Authors: Alfred Wünsche

The Wigner quasiprobability, along with some of its essentialproperties, is introduced and discussed in two versions, first covering real canonical variables such as W(q,p) and second a pair of complex conjugate coordinates such as W(α,α*). The reconstruction of the density operator ϱ of states is also given. Building upon the Susskind–Glogower concept of quantum phase operators, further aspects of phase operator algebras in the quantum optics of a harmonic oscillator are discussed in relation to the realization of the su(1,1) Lie algebra. Coherent phase states |ε⟩ are introduced in analogy to the common coherent states |α⟩ in two ways, as both eigenstates of certain operators and as states generated from a ground state |0⟩ by operators of the Lie group SU(1,1). The limiting transition to the non-normalizable Fritz London phase states |eiφ⟩ on the unit circle and an (over)-completeness relation for the coherent phase states are derived. The Wigner quasiprobability W(q,p) for the coherent phase states is calculated and graphically represented. From the Wigner quasiprobability, a phase distribution W(φ) is calculated by integrating over the radius, and its uncertainty is defined and presented. The Hilbert–Schmidt distance is discussed as a measure of the non-classicality of states, where most of our with Viktor Dodonov work was carried out.

Physics doi: 10.3390/physics8020036

Authors: José Holanda

This paper investigates the control of magnetic energy confinement in one- and three-dimensional magnetic systems by systematically accounting for magnetic interactions. The analysis provides new insight into magnetic behavior at the nanoscale and introduces a simulation-based framework that clearly distinguishes between magnetizing and demagnetizing interaction regimes. Within this framework, magnetic energy confinement is rigorously defined and can be quantitatively controlled through the underlying interaction landscape. To validate this approach, extensive numerical simulations were performed on representative one- and three-dimensional nanostructures, including individual nanowires and hexagonal arrays of nanowires. Each nanowire was modeled as a chain of interacting ellipsoidal grains, enabling an accurate description of the complex magnetic interactions governing energy confinement in these systems.

Physics doi: 10.3390/physics8020035

Authors: Alexander Breev Dmitry Gitman

The relationship between states obtained by the non-commutative integration method of the Schrödinger equation on Lie groups and generalized coherent states is investigated. It is shown that such solutions belong to the class of generalized coherent states when the corresponding λ-representation is real.

Physics doi: 10.3390/physics8020034

Authors: Fernando M. O. Moucherek Ricardo L. L. Vitória

We investigate the effects of Lorentz symmetry violation (LSV) on a scalar particle via a non-minimal coupling in the Klein–Gordon equation within the charge–parity–time CPT-odd gauge sector. Through an analytical approach, we derive bound-state solutions for two distinct anisotropic backgrounds: time-like and space-like. In the time-like case, the LSV induces an effective centrifugal potential, modifying the angular momentum spectrum. When a hard-wall confining potential is included, discrete energy levels emerge, explicitly dependent on the LSV parameters. In the space-like scenario, the particle becomes confined by a Coulomb-type potential induced by the LSV, leading to a quantized energy spectrum that reduces to the free-particle limit when the LSV parameters vanish. Our results illustrate how spacetime anisotropies, encoded in a background vector field, can significantly alter the quantum dynamics of scalar particles in the presence of a magnetic field.

Physics doi: 10.3390/physics8020033

Authors: Galina L. Klimchitskaya Constantine C. Korikov Vladimir M. Mostepanenko

We consider the Casimir force in configurations with magnetic metal plates and analyze the reasons why the predictions of the Lifshitz theory using the dielectric permittivity of the Drude model are inconsistent with the measurement data. For this purpose, the contributions of the electromagnetic waves with the transverse magnetic and transverse electric polarizations to the Casimir force are computed using the Lifshitz theory expressed in terms of the pure imaginary Matsubara frequencies. Furthermore, the fractions of the evanescent and propagating waves in these contributions are found using the equivalent formulation of the Lifshitz theory along the real frequency axis. All computations are performed for Au–Ni and Ni–Ni plates using the Drude model and the experimentally consistent plasma model over the separation region from 0.5 to 6 μm, where the total force value is determined by the conduction electrons. It is shown that the transverse magnetic contribution to the Casimir force does not depend on the model of the dielectric permittivity used, allowing the total difference between the predictions of the Lifshitz theory using the Drude model and the measurement data to be determined by the transverse electric contribution. In doing so, as opposed to the case of nonmagnetic metals, both fractions of the evanescent and propagating waves in this contribution depend on the model of the dielectric permittivity used in computations, whereas the magnetic properties of the plate metal influence the Casimir force solely through the fraction of the propagating waves in the transverse electric contribution. The issue of a more adequate theoretical description of the electromagnetic response of magnetic metals is discussed.

Physics doi: 10.3390/physics8010032

Authors: Grigoris Panotopoulos

The paper investigates the structural properties of self-gravitating fluid spheres composed of a dilute, homogeneous, and ultracold Bose gas, assuming repulsive, short-range interactions. For the first time, the Lee–Huang–Yang (LHY) correction is incorporated to the standard polytropic equation-of-state with index n=1, which extends beyond the Hartree mean-field approximation by accounting for quantum fluctuations. The findings indicate that this correction significantly affects the mass–radius relationships and other properties of condensate dark stars, such as the compactness factor and tidal Love numbers. Notably, the impact of the LHY correction is more pronounced for equations of state that support higher maximum stellar masses.

Physics doi: 10.3390/physics8010031

Authors: Mohamed Babiker

The turning point that sparked the initiation of quantum theory was the Planck–Einstein postulate that the energy of a monochromatic radiation field is quantized in terms of photons, and this was followed by the development of the principles of quantum mechanics. Although some conceptual issues remain to be resolved, quantum mechanics is regarded as a well-established discipline which may lead to the unraveling of the nature of matter in general. Today, the influence of quantum mechanics is evident in its applications, with remarkable technological advances involving diverse aspects of the physical world. What appears to need particular attention, however, (after a hundred years have elapsed since the birth of quantum mechanics) is the impact that the concept of the ‘quantum’ has had beyond traditional quantum mechanics. The paper describes how the ‘quantum’ concept has influenced and continues to influence developments in physical systems, which are essentially classical, in that they are basically governed, entirely, or in part, by non-quantum laws, but in which, the physics is distinguished by its own special quantum—the photon analogue. The paper illustrates this by considering, as prototype examples, bulk plasmons and phonons. The study outlines the systematic quantization of plasmons and phonons, both of the polariton (transverse) forms and their longitudinal forms, and discusseshow these interact with quantum systems such as electrons, atoms, and condensed matter. It is demonstarted using one case, namely, involving longitudinal plasmons, how utilizing quantum concepts and techniques facilitate their interaction with matter, as in electron energy loss spectroscopy.

Physics doi: 10.3390/physics8010030

Authors: Santosh Kumar Kudtarkar

The paper develops a coarse-grained framework for computing mean extinction times in multi-metastable systems modeled as one-step continuous-time Markov chains with an absorbing state. At the microscopic level, backward equations on finite corridors are solved to obtain closed-form series for committors, mean first-passage times, and intrawell (basin) waiting times. A renewal–reward construction then yields effective interwell transition rates written as a success probability divided by a mean cycle duration, providing an interpretable effective rate constant. These rates define a reduced Markov chain on the wells together with extinction; mean extinction times follow from a linear system, and the associated fundamental matrix quantifies pre-extinction residence times in each coarse state. This framework makes explicit how multiple escape pathways and intrawell dwell times contribute to extinction statistics in finite systems. The method is illustrated on a double-well landscape with an extinction state, using a reversible potential-to-rates mapping for the numerical example. Comparisons of alternative intrawell models and validation against exact one-step computations demonstrate accuracy at finite system sizes, including regimes where diffusion approximations are unreliable. The resulting formulas require only local rate data, remain numerically stable under strong bias, and extend directly to multiple wells and flexible boundary conditions.

Physics doi: 10.3390/physics8010029

Authors: Merab Gogberashvili Tinatin Tsiskaridze

We investigate a possible resolution of the dark energy problem within a pair-universe framework, in which the universe emerges as an entangled pair of time-reversed sectors. In this setting, a global zero-energy condition allows vacuum energy contributions from the two sectors to cancel, alleviating the need for extreme fine-tuning. We propose that the observed dark energy does not originate from vacuum fluctuations but instead arises as an effective entanglement energy between the visible universe and its mirror counterpart. Treating the cosmological constant as an integration constant fixed by boundary conditions rather than a fundamental parameter, we show that the cosmological equations can be formulated without explicitly introducing vacuum energy. By imposing physically motivated boundary conditions at the cosmological event horizon, we obtain an integration constant consistent with the observed dark energy density. The parallel mirror world scenario thus provides a unified framework that may simultaneously explain the origins of dark energy and dark matter.

Physics doi: 10.3390/physics8010028

Authors: Yuriy G. Gubarev Jingyue Luo

The problem of controlling plasma is one of the most essential challenges in the creation of experimental facilities for thermonuclear fusion. In this study, a mathematical model of a two-component Vlasov–Poisson plasma is used to study the stability of spatial dynamic equilibria in this plasma. Applying the direct Lyapunov method, we obtain results that demonstrate that three-dimensional (3D) dynamic equilibrium states of the Vlasov–Poisson plasma are absolutely unstable with respect to small spatial perturbations. The sufficient conditions for linear practical instability are obtained for the 3D dynamic equilibria of a two-component Vlasov–Poisson plasma. An a priori exponential lower estimate is constructed, and initial data are found for small spatial perturbations that grow with time. Finally, analytical examples are presented for exact stationary solutions to the mathematical model of Vlasov–Poisson plasma and the growing small 3D perturbations superimposed on these solutions.

Physics doi: 10.3390/physics8010027

Authors: Dmitry Kalashnikov Konstantin Belotsky

As is known, the standard cosmological model (ΛCDM ) demonstrates reasonable agreement with observations of the large-scale structure of the Universe. However, the model shows significant differences between observations of individual galaxies and numerical simulations. To address these discrepancies, various extensions of ΛCDM are being explored, one of which is self-interacting dark matter (SIDM). We employ a SIDM model characterized by a dark Coulomb-like interaction between dark electrons and dark protons and mediated by a dark photon. An essential feature of such models is recombination—the formation of ‘dark atoms’, which can be part of dark matter (DM). The spatial distributions of two-component DM that may explain the positron anomaly have been studied in earlier studies. Our contribution is to calculate three-body recombination rates and the resulting neutral fraction of ‘dark atoms’, as well as to show that the recombination process provides a natural mechanism for generating such two-component DM during the evolution of the Universe.

Physics doi: 10.3390/physics8010026

Authors: Annabel Kropf Ivo Schulthess

This review serves as a conceptual and practical introduction to strong-field quantum electrodynamics (SFQED), written from the standpoint of experimental physicists. Rather than providing a comprehensive theoretical review, the paper focuses on the core ideas, terminology, and challenges in SFQED that are most relevant to experimental design and interpretation. The review serves as a first point of contact with the subject, bridging the gap between foundational theory and hands-on experimental investigations, and complementing more formal literature in the field.

Physics doi: 10.3390/physics8010024

Authors: Carlos Rodriguez-Benites Sergio Santa-María Nelson Mechán-Zurita Kenyi Llauce-Baldera Arnhol Campos-Bocanegra Cristhian Nunura-Cotrina Manuel Gonzales-Hernandez Vaukelyn Viloria-León Moises Barrios-Cespedes Fredy Medina-Gamboa Antonio Rivasplata-Mendoza

We investigate cosmological scenarios in a spatially flat Friedmann–Lemaître–Robertson–Walker (FLRW) universe containing Ricci-type holographic dark energy within the framework of general relativity. The cosmic fluid is composed of baryonic matter, radiation, cold dark matter, and dark energy. We consider three phenomenological interaction schemes in the dark sector and derive analytic expressions for the standard cosmological quantities in each case. Using observational data from cosmic chronometers and Type Ia supernovae (Pantheon sample), we constrain the parameters of the interacting models and determine their best-fit values. Finally, we compare the interacting holographic scenarios with the concordance ΛCDM (Λ cold dark matter) model at the background level, displaying contour plots for the cosmological and interaction parameters and discussing the performance of the models in light of earlier results in the literature.

Physics doi: 10.3390/physics8010025

Authors: Yuan Shi John D. Moody

Magnetic fields, either imposed externally or produced spontaneously, are often present in laser-driven high-energy-density systems. In addition to changing plasma conditions, magnetic fields also directly modify laser–plasma interactions (LPI) by changing the participating waves and their nonlinear interactions. In this paper, we use two-dimensional particle-in-cell (PIC) simulations to investigate how magnetic fields directly affect crossbeam energy transfer (CBET) from a pump to a seed laser beam when the transfer is mediated by the ion-acoustic wave (IAW) quasimode. Our simulations are performed in the parameter space where CBET is the dominant process and in a linear regime, where pump depletion, distribution function evolution, and secondary instabilities are insignificant. We use a Fourier filter to separate out the seed signal and project the seed fields onto two electromagnetic eigenmodes, which become nondegenerate in magnetized plasmas. By comparing the seed energy before CBET occurs and after CBET reaches quasi-steady state, we extract the CBET energy gains for both eigenmodes in lasers that are initially linearly polarized. Our simulations reveal that, starting from a few MG fields, the two eigenmodes have different gains, and magnetization alters the dependence of the gains on laser detuning. The overall gain decreases with magnetization when the laser polarizations are initially parallel, while a nonzero gain becomes allowed when the laser polarizations are initially orthogonal. These findings qualitatively agree with theoretical expectations.

Physics doi: 10.3390/physics8010023

Authors: Slobodan Radošević Sonja Gombar Milica Rutonjski Petar Mali Milan Pantić Milica Pavkov-Hrvojević

We discuss the geometry behind the classical Heisenberg model at the level suitable for third- or fourth-year students who did not have the opportunity to take a course on differential geometry. The arguments presented here rely solely on elementary algebraic concepts such as vectors, dual vectors and tensors, as well as Hamiltonian equations and Poisson brackets in their simplest form. We derive Poisson brackets for classical spins, along with the corresponding equations of motion for the classical Heisenberg model, starting from the two-sphere geometry, thereby demonstrating the relevance of standard canonical procedures in the case of the Heisenberg model.

Physics doi: 10.3390/physics8010022

Authors: Alexei D. Chepelianskii Dima L. Shepelyansky

The quantum dissipative time evolution of a fluxonium under a pulsed field (kicks) is studied numerically and analytically. In the classical limit, the system dynamics is converged to a strange chaotic attractor. The quantum properties of this system are studied using the density matrix within the framework of the Lindblad equation. In the case of dissipative quantum evolution, the steady-state density matrix is converged to a quantum strange attractor that is similar to the classical one. It is shown that depending on the dissipation strength, there is a regime when the eigenstates of the density matrix are localized at a strong or moderate dissipation. At weak dissipation, the eigenstates are argued to be delocalized, which is linked to the Ehrenfest explosion of the quantum wave packet. This phenomenon is related to the Lyapunov exponent and Ehrenfest time for the quantum strange attractor. Possible experimental realizations of this quantum strange attractor with fluxonium are discussed.

Physics doi: 10.3390/physics8010021

Authors: Boris A. Malomed Gennadiy Burlak Gustavo Medina-Ángel Yuri Karlovich

We systematically investigate semiclassical dynamics of the optical field produced by quantum nanoemitters (NEs) embedded in a periodic lattice of conducting nanorings (NRs), in which plasmon polaritons (PPs) are excited. The coupling between PPs and NEs through the radiated optical field leads to establishment of a significant cross-correlation between NEs, so that their internal dynamics (photocurrent affected by the laser irradiation) depends on the NR’s plasma frequency ωp. The transition to this regime, combined with the nonlinearity of the system, leads to a quite increase in the photocurrent in the NEs, as well as to non-smooth (chimera-like or chaotic) behavior in the critical (transition) region, where considerably small variations in ωp lead to significant changes in the level of the NE pairwise cross-correlations. The chimera-like state is realized as coexistence of locally synchronized and desynchronized NE dynamical states. A fit of the dependence of the critical current on ωp is found, being in agreement with results of numerical simulations. The critical effect may help to design new optical devices, using dispersive nanolattices which are made available by modern nanoelectronics.

Physics doi: 10.3390/physics8010020

Authors: R. Guy Woolley

This review explores the foundations of non-relativistic quantum electrodynamics (QED) and its application to atoms and molecules. It follows the traditional route of placing classical electrodynamics in an Hamiltonian framework, followed by Dirac’s canonical quantisation algorithm. The properties of the resulting quantum Hamiltonian are reviewed from a non-perturbative perspective. It discusses the gauge invariance of the S-matrix, the Coulomb interaction, and the challenges posed by infinities in classical and quantum electrodynamics. The paper examines the mathematical frameworks used to address these issues, including the use of distributions and the Colombeau algebra. The review also highlights the limitations of the Coulomb Hamiltonian in explaining molecular structure and chemistry, emphasizing the need for additional theoretical modifications to bridge quantum mechanics and chemical phenomena.

Physics doi: 10.3390/physics8010019

Authors: Vladimir M. Mostepanenko Galina L. Klimchitskaya

We address the spatially nonlocal dielectric functions of graphene at any frequency derived starting from the first principles of thermal quantum field theory using the formalism of the polarization tensor. After a brief review of this formalism, the longitudinal and transverse dielectric functions are considered at any relationship between the frequency and the wave vector. The analytic properties of their real and imaginary parts are investigated at low and high frequencies. Emphasis is given to the double pole at zero frequency, which arises in the transverse dielectric function. The role of this unusual property in solving the problem of disagreement between experiment and theory in the Casimir effect is discussed. We believe that a more complete dielectric response of ordinary metals should also be spatially nonlocal and its transverse part may possess the double pole in the region of evanescent waves.

Physics doi: 10.3390/physics8010018

Authors: Igor Kaganovich Michael Tendler

Partially ionized plasma physics has attracted increased attention recently due to numerous technological applications made possible by the increased sophistication of computer modelling, the depth of the theoretical analysis, and the technological applications to a vast field of manufacturing for computer components. Partially ionized plasma is characterized by a significant presence of neutral particles in contrast to the fully ionized plasma. The theoretical analysis is based upon solutions of the kinetic Boltzmann equation, yielding the non-Maxwellian electron energy distribution function (EEDF), thereby emphasizing the difference with a fully ionized plasma. The impact of the effect on discharges in inert and molecular gases is described in detail, yielding the complex nonlinear phenomena resulting in plasma selforganization. A few examples of such phenomena are given, including the non-monotonic EEDFs in the discharge afterglow in a mixture of argon with the molecular gas NF3; the explosive generation of cold electron populations in capacitive discharges, hysteresis of EEDF in inductively coupled plasmas. Recently, highly advanced computer codes were developed in order to address the outstanding challenges in plasma technology. These developments are briefly described in general terms.

Physics doi: 10.3390/physics8010017

Authors: Evgenii Yu. Prosviryakov Evgenii S. Baranovskii Sergey V. Ershkov Alexander V. Yudin

Polynomial exact solutions of the Navier–Stokes equations for describing micropolar incompressible fluid flows with energy dissipation are reported. The transformation of mechanical energy into thermal energy is taken into account. The heat equation for the Rayleigh function contains the sum of the squares of the components of the Cauchy velocity tensor (the main component for the dissipative function). Unidirectional homogeneous and non-homogeneous fluid flows with moment stresses are considered. The solvability of overdetermined systems for studying homogeneous and non-homogeneous shear flows is studied. The paper pays attention to the exact integration of equations for three-dimensional flows. The construction of classes of exact solutions is carried out first using the Lin–Sidorov–Aristov solution family. In other words, the velocity field depends linearly on part of the coordinates. The coefficients of the linear forms of the velocity field depend on the third coordinate and time. The pressure field and the temperature field are quadratic forms with similar functional arbitrariness. In addition, exact solutions for the velocity field with a nonlinear dependence on part of the coordinates are considered.

Physics doi: 10.3390/physics8010016

Authors: Khakimjan Butanov Maksudbek Baydjanov Hammid Yusupov Komiljon Bobojonov Maksudbek Yusupov Andrey Chaves Khamdam Rakhimov

We investigate time-resolved wave-packet transport in monolayer graphene patterned with asymmetric arrays of circular electrostatic scatterers. Using the Dirac continuum model with a split-operator scheme, we track how transmission evolves with scatterer radius and polarity sequence. To this end, we consider three potential configurations (Samples 1–3). The results reveal a geometry-controlled crossover from near-ballistic propagation at small radii to interference-dominated backscattering at large radii. Sample 1, where the potential exhibit two parallel lines of circles, each line sharing the same potential sign, preserves the highest transmission. Conversely, in Sample 3, where potential signs are intercalated between circles of the same line, the dwell time increases, which produces stronger confinement. As the radius increases, pronounced temporal oscillations emerge due to repeated internal reflections (similar to Fabry–Pérot interferometer), and the radius dependence of the saturated transmission probability exhibits anti-resonant dips that are tunable by geometry and potential magnitude. These behaviors establish simple design rules for graphene nanodevices: small-radius Sample 1 for high-throughput transport, Sample 2 (with inverted potential signs as compared to Sample 1) for broadband suppression, and Sample 3 for finely tunable, interference-based confinement.

Physics doi: 10.3390/physics8010015

Authors: José Tito Mendonça Kyriakos Hizanidis

We compare two different approaches to turbulence: the kinetic theory of solitons and the kinetic theory of quasi-particles. Using the same model equation as the starting point of both descriptions, we compare their properties, advantages, and limitations. We also address the question of whether a gas of solitons be seen as a particular case of a gas of quasi-particles and propose possible strategies leading to a more general theoretical model of wave turbulence.

Physics doi: 10.3390/physics8010014

Authors: Sukhendu Das Adhikary Amar Prasad Misra

We employ a two-dimensional fluid simulation approach to study the nonlinear turbulent dynamics of internal gravity waves (IGWs) in the weakly ionized Earth’s ionospheric F-layer with the effects of Pedersen conductivity. We observe that the presence of Pedersen conductivity leads to the formation of intermediate-scale structures in the velocity potential, along with the development of small-scale density fluctuations. The characteristic turbulent energy spectrum exhibits a non-Kolmogorov scaling of k−2.40 in the presence of Pedersen conductivity, while a Kolmogorov-like k−5/3 scaling is observed when it is absent, where k denotes the wave number. Due to energy loss caused by Pedersen conductivity, the wave’s amplitude reduces gradually with time. The cross-field diffusion coefficient related to the velocity potential also reduces as Pedersen conductivity increases. The results in the F-layer are compared with those in the literature, where the Ampère force and hence the Pedersen conductivity effect were ignored compared to the pressure gradient and gravity forces, as relevant in the Earth’s D-layer.

Physics doi: 10.3390/physics8010013

Authors: Mitsuo Kono Hans L. Pécseli

Models for dual cascades in power-spectra for fully three-dimensional (3D) incompressible turbulence are reviewed and summarized. Special attention is given to analyses where the basic equations for 3D incompressible flows are expanded in terms of the eigenfunctions for the curl-operator. The possibilities for forward and inverse cascades in 3D fluid turbulence are illustrated and quantified. Conditions for dual- and forward-energy cascades in wavenumber space are presented. The forward or unidirectional cascade is found to dominate, a result consistent with the basic physical arguments formulated by vortex-line stretching. The analysis gives additional details to quantify the cascade conditions including dual cascades. Selected initial or boundary value conditions can give transient space or time intervals, where a dual cascade is dominating.

Physics doi: 10.3390/physics8010012

Authors: Jan Weiland Tariq Rafiq

We show how a source-aware fluid closure framework for turbulent transport performs well on the confinement timescale in magnetically confined plasmas. A central result is that whether a source is resonant with the turbulence determines which fluid moments must be retained. Using a nonlinear current formulation, we show that resonance broadening—the dominant kinetic nonlinearity—cancels linear resonances and thereby justifies a quasilinear fluid closure already on the turbulence timescale. We derive a practical negative-energy criterion and identify parameter regimes satisfied by ion-temperature-gradient (ITG) modes (slab and toroidal), with parallel ion compressibility and magnetic curvature controlling the sign. The framework clarifies when velocity-space dynamics must be retained in the kinetic Fokker–Planck equation (for example, for fast-particle instabilities at frequencies about 102 higher than drift-wave frequencies). The present study provides additional support for our model by predicting transport that increases with radius and by showing—consistent with nonlinear kinetic simulations—that the diamagnetic flow dominates the Reynolds stress. Altogether, the results obtained provide a consistent, reduced-cost path to fluid closures that retain the essential kinetic physics while remaining tractable on confinement timescales.

Physics doi: 10.3390/physics8010011

Authors: Suman Kumar Panja Mathias Boström

We present a brief review of a nontraditional but significant application for a high-temperature charged plasma. The unorthodox proposition was made by Barry Ninham concerning a contribution from Casimir forces across high-temperature electron–positron plasma in nuclear interactions. The key message in this review is that high temperatures (about 1011 K) are found to be essential. Certainly, classical, semi-classical, and quantum considerations for the background media impact both the Casimir effect and the physics of stars and the Universe.

Physics doi: 10.3390/physics8010009

Authors: Alexandra V. Rogachevskaya Vasily N. Lednev Pavel A. Sdvizhenskii Igor Y. Savin Sergey V. Gudkov Alexey S. Dorohov Andrey Y. Izmaylov

Laser-induced breakdown spectrometry (LIBS), known as an express analysis technique, is for the first time applied in this study for determining selenium in soil. Modern agriculture requires elemental analysis methods to perform the continuous automated online control of microelement content in soil. However, selenium has never been quantitatively determined in soil by LIBS so far. Different sample preparation techniques (loose soil powder, mounted on adhesive tape and tableted soil) are employed here for LIBS determination of selenium in soil. The optimal choice of analytical line is challenging for selenium because of spectral interference with the minor and major soil components (Fe, Si, Zn, Al, Sb), but the Se I 196.09 nm line has the lowest spectral interference. A limit of detection of 3 mg/kg for selenium in soil is achieved in the present study using LIBS. The analytical performance of tape-mounted and loose soil powder samples with appropriate data averaging is found to be comparable to that achieved for tablets.

Physics doi: 10.3390/physics8010010

Authors: Fernando C. Lombardo Francisco D. Mazzitelli

We analyze shortcuts to adiabaticity (STA) and their completions for the quantum harmonic oscillator (QHO) with time-dependent frequency, as well as for quantum field theory (QFT) in non-stationary backgrounds. We exploit the analogy with one-dimensional quantum mechanics, and the known correspondence between Bogoliubov coefficients in the QHO and transmission/reflection amplitudes in scattering theory. Within this framework, STA protocols for the QHO are equivalent to transmission resonances, while STA in QFT with homogeneous backgrounds correspond to reflectionless potentials. Moreover, using the connection between particle creation and squeezed states, we show how STA completions can be understood in terms of the anti-squeezing operator.

Physics doi: 10.3390/physics8010008

Authors: Alan C. Maioli Evaldo M. F. Curado Jean-Pierre Gazeau Tomoi Koide

We present two complementary approaches to the Gorini–Kossakowski–Sudarshan–Lindblad equation for an open qubit. First, based on linearity, yields solutions illustrated by mixed-state trajectories in the Bloch ball, including non-random asymptotic fixed points and exceptional points. Second, exploiting the SU(2) symmetry, leads to a nonlinear dynamical system that separates angular dynamics from radial dissipation. This symmetry-based perspective presents a promising route toward generalization to open qudits.

Physics doi: 10.3390/physics8010007

Authors: Nuno Crokidakis

The Spanish conquest of the Inca empire in the early 16th century stands as one of the most striking examples of asymmetric historical collapse. In this paper, a simplified mathematical formulation is developed being inspired by Lotka–Volterra dynamics to describe, in a stylized quantitative manner, the interactions between the Inca state and the invading Spanish forces. The model is not intended to explain the historical events in a causal or predictive sense, but rather to capture and represent key mechanisms commonly identified in historical analyses. These include the demographic and political weakening caused by smallpox epidemics prior to direct contact, the internal fragmentation produced by the civil war and the introduction of external shocks such as the capture of Atahualpa and the fall of Cusco. Although intentionally minimalistic, the framework provides a dynamical illustration of how combined internal and external pressures can destabilize a complex society. This descriptive perspective situates the Inca collapse within the broader conceptual language of complex systems, emphasizing how nonlinear interactions, feedback and structural asymmetry shape trajectories of resilience and failure.

Physics doi: 10.3390/physics8010006

Authors: Shuwen Cao Jinhong Yang Shun Lei

Polyurea, a novel spray-applied composite polymer, is of high application importance for rapid roadway support in coal mines. The current study investigates the dynamic process and mechanisms governing the impact and spreading of polyurea droplets on rough surfaces through experimental and theoretical approaches. The key novelty lies in revealing how spontaneously varying viscosity couples with surface microstructure to produce novel scaling laws distinct from classical Newtonian behavior. The droplet impact and wetting process can be divided into three stages. In the pinning stage, droplet behavior is dominated by kinetic energy, leading to inertia-driven spreading in which the contact line radius increases quite slowly with time. In the penetration stage, the apparent three-phase contact line (TPCL) is pinned by surface microstructures, while the real TPCL evolves with time following a temporal scaling law t3/2. In the spreading stage, surface roughness becomes decisive. On low-roughness substrates, limited pinning allows the real and apparent TPCLs to spread synchronously, with TPCL evolution governed by surface tension and viscous forces, following a t1/8 scaling law. As roughness increases, pinning effects strengthen, causing divergence: the real TPCL is driven by surface tension and viscous dissipation between microstructures, whereas the apparent TPCL is additionally influenced by pinning and reaction-induced viscosity, scaling as t1/24. This t1/24 scaling for the apparent contact line on relatively high-roughness surfaces represents a significant deviation from established scaling relations. Experiments on rock-like substrates confirm these mechanisms for polyurea droplets. These findings provide theoretical and engineering guidance for optimizing spray-coating parameters in coal mines, with the goal of improving coating uniformity and interfacial adhesion.

Physics doi: 10.3390/physics8010005

Authors: Erik O. Shalenov Yerkhan A. Tashkenbayev Yeldos S. Seitkozhanov Karlygash N. Dzhumagulova

We present the effective optical potential describing the interaction between an electron and a neon atom in a dense plasma. This potential accounts not only for the screening effect but also for the quantum non-locality and electronic correlation effects, which lead to an increase in the interaction energy between the electron and the neon atom. Within this framework, differential and momentum transport cross-sections for elastic electron–neon scattering are determined. The obtained results are compared with the available experimental data and theoretical predictions, showing exceptionally good agreement.

Physics doi: 10.3390/physics8010004

Authors: Grégoire Salomon Mathias Rapacioli J. Christian Schön Nathalie Tarrat

The environmental pollution caused by emerging organic contaminants—such as ibuprofen—is becoming increasingly a cause for alarm. New treatments for their removal are currently being developed, but the nature and toxicity of the transformation products (TPs) formed during the processes cannot be readily assessed experimentally. Atomistic simulations are thus of high interest in predicting the chemical structure of these TPs. In this paper, we demonstrate that the transformation of a contaminant molecule under irradiation can be studied using the threshold algorithm combined with the density functional-based tight-binding (DFTB) method. The fragmentation pathways of an ibuprofen molecule under irradiation are studied as a function of the energy added to the system. Specifically, the chemical structures of ibuprofen’s TPs, the paths between them, their stabilities, probabilities of occurrence, and the related mass spectra were obtained as a function of the amount of energy absorbed. We also simulated the evolution of the ibuprofen molecule as a function of the number of pulses, i.e., for a sequence of energy depositions. A dominant fragmentation scheme is identified, where first the OH group is released, followed by the loss of the CO group. The photon energy and the number of pulses are found to be key parameters for the selection of this degradation route among all identified fragmentation pathways.

Physics doi: 10.3390/physics8010003

Authors: Svetlana Sofronova Artem Chernyshev Anna Selyanina Aleksandr Krylov Timofey Tislenko

First-principles calculations of the structural and magnetic properties of kotoite Ni2Co(BO3)2 are carried out. The minimization of the lattice parameters shows the values to be in good agreement with the experimental data (the difference is less than 1%). The atomic coordinates are calculated. Cobaltions are found tending to occupy position 2a and nickel ions tending to occupy position 4f. The same magnetic cell as in Ni3(BO3)2, but quadrupled in size (2a × b × 2c), found having the minimum exchange energy for Ni2Co(BO3)2. In Ni2Co(BO3)2, the magnetic moments are obtained oriented along the baxis, similar to that in Co3(BO3)2.

Physics doi: 10.3390/physics8010002

Authors: Andrea Addazi Salvatore Capozziello Giuseppe Meluccio

The cosmological constant (CC, Λ) problem stands as one of the most profound puzzles in the theory of gravity, representing a remarkable discrepancy of about 120 orders of magnitude between the observed value of dark energy and its natural expectation from quantum field theory. This paper synthesizes two innovative paradigms—holographic naturalness (HN) and pre-geometric gravity (PGG)—to propose a unified and natural resolution to the problem. The HN framework posits that the stability of the CC is not a matter of radiative corrections but rather of quantum information and entropy. The large entropy SdS∼MP2/Λ of the de Sitter (dS) vacuum (with MP being the Planck mass) acts as an entropic barrier, exponentially suppressing any quantum transitions that would otherwise destabilize the vacuum. This explains why the universe remains in a state with high entropy and relatively low CC. We then embed this principle within a pre-geometric theory of gravity, where the spacetime geometry and the Einstein–Hilbert action are not fundamental, but emerge dynamically from the spontaneous symmetry breaking of a larger gauge group, SO(1,4)→SO(1,3), driven by a Higgs-like field ϕA. In this mechanism, both MP and Λ are generated from more fundamental parameters. Crucially, we establish a direct correspondence between the vacuum expectation value (VEV) v of the pre-geometric Higgs field and the de Sitter entropy: SdS∼v (or v3). Thus, the field responsible for generating spacetime itself also encodes its information content. The smallness of Λ is therefore a direct consequence of the largeness of the entropy SdS, which is itself a manifestation of a large Higgs VEV v. The CC is stable for the same reason a large-entropy state is stable: the decay of such state is exponentially suppressed. Our study shows that new semi-classical quantum gravity effects dynamically generate particles we call “hairons”, whose mass is tied to the CC. These particles interact with Standard Model matter and can form a cold condensate. The instability of the dS space, driven by the time evolution of a quantum condensate, points at a dynamical origin for dark energy. This paper provides a comprehensive framework where the emergence of geometry, the hierarchy of scales and the quantum-information structure of spacetime are inextricably linked, thereby providing a novel and compelling path toward solving the CC problem.

Physics doi: 10.3390/physics8010001

Authors: Kalamkas Astemessova Medeu Abishev Nurzada Beissen Tursynbek Yernazarov Daulet Berkimbayev Sulukas Sarsenbayeva Nurkamal Shynggyskhan Bekzat Zhumabay Gulzhan Turlybekova

We consider a model problem of polarization-dependent light bending and time delays in the vicinity of neutron stars endowed with magnetar-strength magnetic fields (B∼1015G), combining an effective-metric formulation of Heisenberg–Euler nonlinear electrodynamics with general-relativistic ray tracing. The spacetime geometry is analyzed using both the Kerr metric and a quadrupole-deformed q-metric, characterized by a quadrupole parameter varying in the range q∈[10−3,0.5]. In addition, the impact of complex magnetic-field topologies is examined by introducing a magnetic quadrupole component alongside the dipole configuration. The simulations performed in this study demonstrate that the inclusion of the quadrupole deformation parameter significantly modifies photon trajectory deflections compared to the standard Kerr solution. We further quantify the geometric dilution of the photon beam, finding a cross-section expansion ratio of approximately 4.7×1013 for rays reaching Earth. This strong dilution imposes stringent constraints on the detectability of polarization-dependent signatures and time-delay echoes. Finally, characteristic illustrations are presented for trajectory distortions, bending-angle distributions, and intensity valleys produced by the combined gravitational and magnetic lensing effects.

Physics doi: 10.3390/physics7040068

Authors: Nabil Benzerroug Karim Choubani Mohamed Ben Rabha Mohsen Choubani

By solving the three-dimensional Schrödinger equation with a second-order implicit Finite Difference Method (FDM), the combined effects of temperature, morphology, hydrostatic pressure, and transverse electric field on the nonlinear optical rectification (NOR) of GaAs/AlεGa1−εAs elliptical quantum rings are examined. The NOR amplitude is twelve times enhanced and a noticeable blue shift is induced in the THz region when the electric field is increased. Consequently, with the electric field of 1 × 105 V/m, the NOR magnitude achieves its maximum value of 17.116 × 105 m/V. Additionally, when the electric field is aligned along one side of the system’s in-plane cross-section, the strongest amplification takes place. However, with corresponding spectrum shifts, the NOR intensity rises with temperature and falls with hydrostatic pressure. Additionally, changing the transverse profile of the quantum ring from triangular to parabolic broadens the carrier wave functions and has a considerable impact on the NOR coefficient. These findings provide important information for the construction of high-performance, tunable THz optoelectronic devices by demonstrating effective external and structural tuning of NOR.

Physics doi: 10.3390/physics7040067

Authors: Uriel Rivera-Ortega Antonio Barcelata-Pinzon Griselda Saldaña-Gonzalez

In this study, we present the custom development and implementation of a mobile application designed specifically to experiment with Malus’s law, leveraging the integration of a LEGO EV3 and the light sensor of a mobile device. Unlike previous studies that utilize pre-designed mobile applications, our approach focuses on creating a tailored solution that meets the unique requirements of this optical experiment. Using MIT App Inventor, we developed a customized interface that allows for the rotation of polarizers controlled by motors connected to a LEGO EV3 while simultaneously measuring the light intensity using the mobile’s light sensor. The block-based programming in App Inventor facilitates the application of programming concepts in creating physics experiments in a straightforward manner. This innovative approach not only facilitates the understanding of fundamental optical concepts but also integrates accessible technology to enrich the educational experience in physics, offering a customizable solution adaptable to various educational settings. Preliminary results indicate a significant improvement in students’ comprehension of optical polarization principles, demonstrating the effectiveness of our approach.

Physics doi: 10.3390/physics7040066

Authors: Olga V. Man’ko

The quantizer–dequantizer method is employed. Using the construction of probability distributions describing density operators of a quantum system states, the connection between the Feynman path integral and the time evolution of the density operator (Landau density matrix) as well as the wave function of the stateconsidered. For single–mode systems with continuous variables, a tomographic propagator is introduced in the probability representation of quantum mechanics. An explicit expression for the probability in terms of the Green function of the Schrödinger equation is obtained. Equations for the Green functions defined by arbitrary integrals of motion are derived. Examples of probability distributions describing the evolution of state of a free particle, as well as states of systems with integrals of motion that depend on time (oscillator type) are discussed.

Physics doi: 10.3390/physics7040065

Authors: Alexander Volyar Mikhail Bretsko Yana Akimova

Over the past thirty years, the focus in singular optics has been on structured beams carrying orbital angular momentum (OAM) for diverse applications in science and technology. However, as practice has shown, the OAM-free structured Gaussian beams with several degrees of freedom are no worse than the OAM beams, especially when propagating through turbulent flows. In this paper, we partially fillthis gap by theoretically and experimentally mapping cyclic changes in vortex-free states (including OAM) as a phase portrait of the beam evolution in an astigmatic optical system. We show that those cyclic variations in the beam parameters are accompanied by the accumulation of the geometric Berry phase, which is an additional degree of freedom. We find also that the geometric phase of cyclic changes in the intensity ellipse shape does not depend on the radial numbers of the Laguerre–Gaussian mode with zero topological charge and is always set by changing the shape of the Gaussian beam. The Stokes parameter formalism was developed to map the beam states’ evolution onto a Poincaré sphere based on physically measurable second-order intensity moments. Theory and experiment are found to be in a good enough agreement.

Physics doi: 10.3390/physics7040064

Authors: Sayabek Sakhiyev Kylyshbek Turlybekuly Asset Shaimerdenov Darkhan Sairanbayev Avganbek Sabidolda Zhanibek Kurmanaliyev Akzhol Almukhametov Olzhas Bayakhmetov Ruslan Kiryanov Ekaterina Korobkina Egor Lychagin Alexey Muzychka Valery Nesvizhevsky Cole Teander Khac Tuyen Pham

We present the concept of an ultracold neutron (UCN) source with a superfluid He-4 (SF 4He) converter located in the thermal column of the WWR-K research reactor at the Institute of Nuclear Physics (INP) in Almaty, Kazakhstan. The conceptual design is based on the proposal of accumulating UCNs in the source and effectively transporting them to experimental setups. We propose to improve the UCN density in the source by separating the heat and UCN transport from the production volume and decreasing the temperature of the SF 4He converter to below about 1 K. To obtain operation temperatures below 1 K, we plan to use a He-3 pumping cryogenic system and minimize the thermal load on the UCN accumulation trap walls. Additional gain in the total number of accumulated UCNs can be achieved through the use of a material with a high critical velocity for the walls of the accumulation trap. The implementation of such a design critically depends on the availability of materials with specific UCN and cryogenic properties. This paper describes the conceptual design of the source, discusses its implementation methods and material requirements, and plans for material testing studies.

Physics doi: 10.3390/physics7040063

Authors: Helena Cristina Vasconcelos Maria Gabriela Meirelles

We establish a general, device-oriented procedure to extract absolute pump-band metrics from room-temperature UV–Vis (ultraviolet–visible) absorbance—including the absorption coefficient α(λ), per-active-ion cross-section σeffλ, the effective per-active-ion absorption cross section σeffλ and derivative-based line-shape descriptors. As a representative case study, the procedure is applied to nanocrystalline Er3+/Ho3+:Y3Ga5O12 over the 350–700 nm spectral range. After baseline correction and line-shape inspection assisted by the numerical second derivative of the absorbance, we extract conservative peak positions and the full width at half maximum across the visible 4f–4f manifolds. At the technologically relevant pump wavelengths near 406 nm (Er-addressing) and 473 nm (Ho-addressing) bands, resulting absorption coefficients are α = 0.313 ± 0.047 cm−1 and α = 0.472 ± 0.071 cm−1, respectively. The corresponding per-active-ion σeff of (3.62 ± 0.54) × 10−22 cm2 and (5.46 ± 0.82) × 10−22 cm2, referenced to the measured optical path length L = 0.22 ± 0.03 mm (approximately 15% propagated relative uncertainty; explicit 1/L rescaling). Cross sections are reported per total active-ion density (Er3+ + Ho3+). The spectra exhibit Stark-type substructure only partially resolved at room temperature; the second derivative highlights hidden components, and we report quantitative descriptors (component count, mean spacing, curvature-weighted prominence, and pump detuning) that link line-shape structure to absolute pump response. These device-grade metrics enable rate-equation modelling (pump thresholds, detuning tolerance), optical design choices (path length, single/multi-pass or cavity coupling), and host-to-host benchmarking at 295 K. The procedure is general and applies to any rare-earth-doped material given an absorbance spectrum and path length.

Physics doi: 10.3390/physics7040062

Authors: Min-Chang Lee

BU–MIT whistler wave injection experiments, which were conducted at Arecibo Observatory, started with the joint US–USSR Active Space Plasma Program Experiment on 24 December 1989. In this experiment, a satellite-borne VLF transmitter injected radio waves at the frequency and power of 10 kHz and 10 kW. A series of controlled whistler wave experiments with the Arecibo HF heater were subsequently carried out during 1990–1998 until the HF heater was damaged by Hurricane Georges in 1998. In these ionospheric HF heating experiments, 28.5 kHz whistler waves were launched from the nearby naval transmitter (code-named NAU) located at Aguadilla, Puerto Rico. HF heater waves were used to create ionospheric ducts (in the form of parallel-plate waveguides) to facilitate the entry of NAU whistler waves from the neutral atmosphere into the ionosphere. Conjugate whistler wave propagation experiments were conducted between Arecibo, Puerto Rico and Trelew, Argentina in 1997. After 1999, whistler wave experiments in the absence of an HF heater had been conducted. Naturally-occurring large-scale ionospheric irregularities due to spread F or Traveling Ionospheric Disturbances (TIDs) were relied on to guide NAU launched 40.75 kHz whistler waves to propagate from the ionosphere further into the radiation belts, to cause 390 keV charged-particle precipitation. A train of TIDs, resulting from the 9.2 Mw earthquake off the west coast of Sumatra, Indonesia, was observed in our 26 December 2004 Arecibo experiments, about a day after the earthquake-launched tsunami waves traveled across the Indian Ocean, then into remote parts of the Atlantic Ocean. The author’s recent research efforts, motivated by Arecibo experiments, focus on Solar Powered Microwave Transmitting Systems, to simulate Solar Energy Harvesting via Solar Power Satellite (SPS) (also known as Space Based Solar Power (SBSP)) These experiments involved a large number of the author’s BU and MIT students working on theses and participating in the Undergraduate Research Opportunities Program (UROP), in collaboration with other colleagues at several universities and national laboratories.

Physics doi: 10.3390/physics7040061

Authors: Lucas Veneziani de Toledo Breno Justen de Castro Moreira Leonardo Rodrigues Cadorim Edson Sardella

This study investigates the influence of inelastic electron–phonon collision time (τe-ph) on the behavior of the resistive state of three-dimensional superconducting systems. Using the generalized time-dependent Ginzburg–Landau formalism, we model the interplay between vortex dynamics, energy dissipation, and thermal effects across varying values of the dimensionless parameter γ proportional to τe-ph and different values of the Ginzburg–Landau parameter. The results show that larger values of γ enhance the superconducting state by delaying the transition to the normal state, modulating critical currents, and altering differential resistance. An exponential relationship between the upper critical current and γ is observed, indicating prolonged resistive states as the inelastic electron–phonon collision time becomes larger. Furthermore, the study investigates the maximum local peaks in the differential resistance curves, revealing their exponential decay with increasing γ.

Physics doi: 10.3390/physics7040060

Authors: Simon Gluzman

Scaling of the cost-functional and its violations are discussed with regard to their application to the summation of asymptotic truncated expansions. A new family of cost-functionals dependent only on amplitudes is considered, allowing for a continuous breaking of scaling. Cost-functionals can be a homogeneous function of the second order with respect to the scaling of all amplitudes with the same multiplicative factor. However, non-homogenous cost-functionals do violate scaling. A robust and accurate calculation of amplitudes emergent at quite a large value of the variable from the truncated series obtained for relatively small values of the variable is performed using the cost-functional technique with varying degrees of scaling violation. Various physical examples from field theory, quantum mechanics, and statistical physics are considered. Certain parallels with complex systems are noticed and discussed.

Physics doi: 10.3390/physics7040059

Authors: Spencer Kuo Min-Chang Lee Arnold Snyder Brenton Watkins

Analysis of nonlinear plasma waves, formulated and applied for ionospheric HF heating experiments, indicates that Langmuir/upper hybrid waves excited by parametric instabilities can evolve into traveling solitary waves accompanied by self-induced cavitons. To explore these cavitons, a digisonde operating in fast mode was utilized. Significant results were observed in ionograms recorded two minutes after the activation of the O-mode heater. These ionograms displayed two distinct bumps in the virtual height spread, located slightly below both the HF reflection height and the upper hybrid resonance height. It is notable that these heights are also slightly below the excitation regions where Langmuir/upper hybrid Parametric Decay Instabilities (PDIs) are typically generated by an O-mode HF heater. These observations correlate with the theory and provide valuable insights into the dynamics of nonlinear plasma waves and their interaction with the ionosphere during HF heating experiments.

Physics doi: 10.3390/physics7040058

Authors: Yuefeng Li Benchu Lu Huijie Xue Ning Wang Dongmei Cai

The Zernike polynomial method is extensively used for atmospheric phase screen generation but is limited by insufficient high-frequency components. Calculating higher-order terms introduces challenges in computational efficiency and numerical instability when using the direct method. This paper analyzes these issues and proposes replacing the direct method with recursive radial formulas. We evaluate four recursive algorithms (Barmak’s, q-recursive, Prata’s and Kintner’s) for their performance in phase screen generation, focusing on computational speed and numerical stability. Our results demonstrate that recursive methods achieve a 10–20-times improvement in computational efficiency and maintain numerical stability even for high-order expansions. The main novelty of this study lies in the comprehensive comparison and validation of these recursive strategies for high-accuracy atmospheric phase screen simulation.

Physics doi: 10.3390/physics7040057

Authors: Henrique R. Martins-Fontes Fernando S. Navarra

The multiplicity distributions measured in proton–proton collisions at the LHC exhibit appealing new features. One of them is the appearance of a substructure—the so-called “shoulder”—at relatively large multiplicities. The most natural interpretation of this behavior is the existence of two particle-production mechanisms. The final result is then a superposition of two distributions. In our recent paper, we assumed that the two production mechanisms are soft and semihard partonics scatterings. In this paper, we further discuss this assumption, and, in particular, we study the dependence of the results on the scale that separates soft from hard events.

Physics doi: 10.3390/physics7040056

Authors: Luiz Augusto Stuani Pereira Carlos Alberto Tello Sáenz

We investigate the dependence of the maximum etched track length (Lmax) on alpha-particle energy and incidence angle in LR-115 type II nuclear track detectors by combining Geant4 Monte Carlo simulations with controlled chemical etching experiments. The bulk (VB) and track (VT) etch rates were determined under standardized conditions, yielding VB=(3.1±0.1) µm/h and VT=(5.98±0.06) µm/h, which correspond to a critical detection angle of about (58.8±1.2)°. Simulations covering initial energies spanning 1 MeV to 5 MeV and incidence angles up to 70° confirmed that the maximum etched track length varies quadratically with particle energy E and depends systematically on incidence angle θ. Empirical parameterizations of Lmax(E,θ) were obtained, and energy thresholds for complete track registration within the 12 µm sensitive layer were established. The angular acceptance predicted by the VT/VB ratio was validated, and the results demonstrate that Lmax provides a monotonic and more reliable observable for energy calibration compared to track diameter. These findings improve the quantitative calibration of LR-115 detectors and strengthen their use in environmental radon monitoring, radiation dosimetry, and alpha spectrometry. In addition, they highlight the utility of Geant4-based modeling for refining solid state nuclear track detector response functions and guiding the development of optimized detector protocols for nuclear and environmental physics applications.

Physics doi: 10.3390/physics7040055

Authors: Riasat Ali Tiecheng Xia Rimsha Babar

This paper analyzes how the generalized uncertainty principle (GUP) affects the thermodynamic properties in a regular black hole spacetime in the context of f(Q,BQ) symmetric teleparallel gravity, with an arbitrary action f as a function of non-metric scalar Q and the boundary BQ. We analyze a GUP-influenced semi-classical technique in regular black hole spacetime that incorporates the quantum tunneling mechanism. The GUP-influenced temperature results show that the GUP term reduced the vector particles’ radiation in the context of f(Q,BQ) gravity. Moreover, we explore the GUP-influenced entropy as well as the GUP-influenced emission energy, it can help to explain the complex interactions between quantum gravity and astrophysics and highlights the important role of GUP-influenced thermodynamic properties (Hawking temperature, entropy and emission energy) in regular black hole spacetime in the context of f(Q,BQ) gravity. We graphically analyze the effects of different parameters on black hole geometry.

Physics doi: 10.3390/physics7040054

Authors: Alexander R. Karimov Grigoriy O. Buyanov

Based on the hydrodynamic description, the dynamics of nonlinear cylindrical waves in an isentropic plasma are investigated. The problem is considered in an electrostatic formulation for a two-dimensional plasma medium where ions form a stationary background. Proceeding from the particular, exact solution of hydrodynamic equations, we obtain the system of differential equations which describes the electron’s dynamics, taking into account the finite temperature of electrons. Moreover, we find the conditions when this system is reduced to the generalized Ermakov–Pinney equation which was used for analyzing electron dynamics. In the present calculations, a parabolic-in-radius temperature profile was used, associated with an electron density varying only with time. In the framework of the model that worked out, the influence of initial conditions and thermal effects on the regular and singular dynamics of excited waves are discussed. It is shown that the development of singular behavior due to intrinsic nonlinearity is avoided by taking into account thermal effects and the initial rotation of the electron flow.

Physics doi: 10.3390/physics7040053

Authors: Oleg M. Gradov

The effect of the curvature of the boundary of semi-infinite cold plasma on the parameters and properties of surface oscillations localized near this boundary is considered. An analytical description of various cases of the impact of static deformation of the plasma boundary on the characteristics of the oscillating surface charge is obtained, and the results of the exact numerical solution of the initial equations are found to confirm the reliability of the derived analytical formulas. A significant role of the boundary perturbation shape in the formation of the spatial distribution of surface oscillation parameters is revealed. With the help of analytical formulas and precise numerical calculations, a description of this nonlinear interaction is presented. The availability of such a description is crucial both for determining the possibility of using the examined effect for specific applications and, on the other hand, for exciting it in plasma, which requires knowledge of the field structure features.

Physics doi: 10.3390/physics7040052

Authors: Abdel Nasser Tawfik Salah G. Elgendi Sameh Shenawy Mahmoud Hanafy

By extending the four-dimensional semi-Riemann geometry to higher-dimensional Finsler/Hamilton geometry, the canonical quantization of the fundamental metric tensor of general relativity, i.e., an approach that tackles a geometric quantity, is derived. With this quantization, the smooth continuous Finsler structure is transformed into a quantized Hamilton structure through the kinematics of a free-falling quantum particle with a positive mass, along with the introduction of the relativistic generalized uncertainty principle (RGUP) that generalizes quantum mechanics by integrating gravity. This transformation ensures the preservation of the positive one-homogeneity of both Finsler and Hamilton structures, while the RGUP dictates modifications in the noncommutative relations due to integrating consequences of relativistic gravitational fields in quantum mechanics. The anisotropic conformal transformation of the resulting metric tensor and its inverse in higher-dimensional spaces has been determined, particularly highlighting their translations to the four-dimensional fundamental metric tensor and its inverse. It is essential to recognize the complexity involved in computing the fundamental inverse metric tensor during a conformal transformation, as it is influenced by variables like spatial coordinates and directional orientation, making it a challenging task, especially in tensorial terms. We conclude that the derivations in this study are not limited to the structure in tangent and cotangent bundles, which might include both spacetime and momentum space, but are also applicable to higher-dimensional contexts. The theoretical framework of quantization of general relativity based on quantizing its metric tensor is primarily grounded in the four-dimensional metric tensor and its inverse in pseudo-Riemannian geometry.

Physics doi: 10.3390/physics7040051

Authors: Krzysztof Stasiewicz

The applicability of the first-order Fermi mechanism—a cornerstone of the diffusive shock acceleration (DSA) model—in explaining the cosmic ray spectrum is reexamined in light of recent observations from the Magnetospheric Multiscale (MMS) mission at Earth’s bow shock. It is demonstrated that the Fermi and DSA mechanisms lack physical justification and should be replaced by the physically correct ballistic surfing acceleration (BSA) mechanism. The results show that cosmic rays are energized by the convection electric field during ballistic surfing upstream of quasi-perpendicular shocks, independently of internal shock processes. The spectral index of cosmic rays is determined by the magnetic field compression and shock geometry: the acceleration is strongest in perpendicular shocks and vanishes in parallel shocks. The BSA mechanism reproduces the observed spectral indices, with s=−2.7 below the knee at 1016 eV and s=−3 above it. It is suggested that the spectral knee may correspond to particles whose gyroradii are comparable to the characteristic size of shocks in supernova remnants. The acceleration time to reach the knee energy, as predicted by the BSA, is in the order of 500 years.

Physics doi: 10.3390/physics7040050

Authors: Rudrapriya Das Anjali Sharma Susanne Glaessel Supriya Das

One of the main goals of the Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR) is to investigate the properties of strongly interacting matter under high baryon densities and explore the QCD phase diagram. Fluctuations of conserved quantities like baryon number, electric charge, and strangeness are key probes for phase transitions and critical behavior, as are connected to thermodynamic susceptibilities predicted by lattice QCD calculations. In this paper, we report on up-to-the-fourth-order cumulants of (net-)proton number distributions in gold–gold ion collisions at the nucleon–nucleon center of mass energies sNN = 3.5–19.6 GeV using the Parton–Hadron-Quantum-Molecular Dynamics (PHQMD) model. Protons and anti-protons are selected at midrapidity (|y| < 0.5) within a transverse momentum range 0.4 <pT< 2.0 GeV/c of STAR experiment and 1.08 <y< 2.08 and 0.4 <pT< 2.0 GeV/c of CBM acceptances. The results obtained from the PHQMD model are compared with the existing experimental data to undersatand potential signatures of critical behavior and to probe the vicinity of the critical end point in the CBM energy range. The results obtained here with the PHQMD calculations for κσ2 (the distribution kurtosis times variance squared) are consistent with the overall trend of the measurement results for the most central (0–5% centrality) collisions, although the calculations somewhat overestimate the experimental values.

Physics doi: 10.3390/physics7040049

Authors: David L. Andrews

Molecular quantum electrodynamics is a powerful and effective tool for the representation and elucidation of optical interactions with matter. Its history spans nearly a century of significant advances in its detailed theory and applications, and in its wider appreciation. To fully appreciate the development of the subject into its modern form invites a perspective on progressive technical progress in the theory, noting a growth in applications that closely mirrors advances in optical experimentation. The challenges and deficiencies of alternative approaches to theory are also taken into consideration.

Physics doi: 10.3390/physics7040048

Authors: Francisco M. Fernández

This paper for the first time derives some properties of the hydrogen atom inside a box with an impenetrable wall. Scaling of the Hamiltonian operator proves to be practical for the derivation of some general properties of the eigenvalues. The radial part of the Schrödinger equation is conditionally solvable and the exact polynomial solutions provide helpful information. There are accidental degeneracies that take place at particular values of the box radius, some of which can be determined from the conditionally-solvable condition. Some of the roots stemming from the conditionally-solvable condition appear to converge towards the critical values of the model parameter. This analysis is facilitated by the Rayleigh–Ritz method that provides accurate eigenvalues.

Physics doi: 10.3390/physics7040047

Authors: Tatiana Mihaescu Mihai A. Macovei Aurelian Isar

The steady-state quantum dynamics of a compound sample consisting of a semiconductor double-quantum-dot (DQD) system, non-linearly coupled with a leaking superconducting transmission line resonator, is theoretically investigated. Particularly, the transition frequency of the DQD is taken to be equal to the doubled resonator frequency, whereas the inter-dot Coulomb interaction is considered weak. As a consequence, the steady-state quantum dynamics of this complex non-linear system exhibit sudden changes in its features, occurring at a critical DQD-cavity coupling strength, suggesting perspectives for designing on-chip microwave quantum switches. Furthermore, we show that, above the threshold, the electrical current through the double-quantum dot follows the mean photon number into the microwave mode inside the resonator. This might not be the case any more below that critical coupling strength. Lastly, the photon quantum correlations vary from super-Poissonian to Poissonian photon statistics, i.e., towards single-qubit lasing phenomena at microwave frequencies.

Physics doi: 10.3390/physics7040046

Authors: Desejo Filipeson Sozinando Bernard Xavier Tchomeni Alfayo Anyika Alugongo

In this study, a nonlinear dynamic model is developed to examine the stability and vibration behavior of a self-balancing electric Segway operating over irregular stochastic terrains. The Segway is treated as a three-degrees-of-freedom cart–inverted pendulum system, incorporating elastic and damping effects at the wheel–ground interface. Road irregularities are generated in accordance with international standard using high-order filtered noise, allowing for representation of surface classes from smooth to highly degraded. The governing equations, formulated via Lagrange’s method, are transformed into a Lorenz-like state-space form for nonlinear analysis. Numerical simulations employ the fourth-order Runge–Kutta scheme to compute translational and angular responses under varying speeds and terrain conditions. Frequency-domain analysis using Fast Fourier Transform (FFT) identifies resonant excitation bands linked to road spectral content, while Kernel Density Estimation (KDE) maps the probability distribution of displacement states to distinguish stable from variable regimes. The Lyapunov stability assessment and bifurcation analysis reveal critical velocity thresholds and parameter regions marking transitions from stable operation to chaotic motion. The study quantifies the influence of the gravity–damping ratio, mass–damping coupling, control torque ratio, and vertical excitation on dynamic stability. The results provide a methodology for designing stability control systems that ensure safe and comfortable Segway operation across diverse terrains.

Physics doi: 10.3390/physics7040045

Authors: Salomon S. Mizrahi

In special relativity, particle trajectories, whether mass-bearing or not, can be traced on the Minkowski spacetime manifold in (3+1)D. Meantime, in quantum mechanics, trajectories in the phase space are not strictly outlined because coordinate and linear momentum cannot be measured simultaneously with arbitrary precision since they do not commute within the Hilbert space formalism. However, from the density matrix representing a quantum system, the extracted information still produces an imperative description of its properties and, furthermore, by appropriately reordering the matrix entries, additional information can be obtained from the same content. Adhering to this line of work, the paper investigates the definition and the meaning of velocity and speed in a typical quantum phenomenon, the disentanglement for a bipartite system when dynamical evolution is displayed in a (3+1)D pseudo-spacetime whose coordinates are constructed from combinations of entries to the density matrix. The formalism is based on the definition of a Minkowski manifold with compact support, where trajectories are defined following the same reasoning and formalism present in the Minkowski manifold of special relativity. The space-like and time-like regions acquire different significations referred to entangled-like and separable-like, respectively. The definition and the sense of speed and velocities of disentanglement follow naturally from the formalism. Depending on the dynamics of the physical state of the system, trajectories may meander between regions of entanglement and separability in the space of new coordinates defined on the Minkowski manifold.

Physics doi: 10.3390/physics7040044

Authors: Galina L. Klimchitskaya Vladimir M. Mostepanenko

We review and as well obtain some new results on the temperature dependence of spatially nonlocal response functions of graphene and their applications to the calculation of both the equilibrium and nonequilibrium Casimir and Casimir–Polder forces. After a brief summary of the properties of the polarization tensor of graphene obtained within the Dirac model in the framework of quantum field theory, we derive the expressions for the longitudinal and transverse dielectric functions. The behavior of these functions at different temperatures is investigated in the regions below and above the threshold. Special attention is paid to the double pole at zero frequency, which is present in the transverse response function of graphene. An application of the response functions of graphene to the calculation of the equilibrium Casimir force between two graphene sheets and the Casimir–Polder forces between an atom (nanoparticle) and a graphene sheet is considered with due attention to the role of a nonzero energy gap, chemical potential and a material substrate underlying the graphene sheet. The same subject is discussed for out-of-thermal-equilibrium Casimir and Casimir–Polder forces. The role of the obtained and presented results for fundamental science and nanotechnology is outlined.

Physics doi: 10.3390/physics7030043

Authors: Mina Shiri Mehrdad Ghominejad Mohammad Reza Pourkarimi Saeed Haddadi

Measurement uncertainty limits how precisely information can be extracted from quantum systems due to inherent quantum indeterminacy. On the other hand, dense coding capacity quantifies the amount of classical information that can be sent using shared entanglement, thereby enhancing communication efficiency beyond classical limits. In this paper, we investigate these two concepts for a spin-star network under an external magnetic field under a thermal regime, considering both homogeneous and inhomogeneous models. We reveal that under certain conditions, dense coding capacity not only becomes valid but is also optimized, implying that measurement uncertainty is significantly suppressed. Furthermore, we analyze the local quantum uncertainty of the thermal state under the influence of decoherence channels to assess the effectiveness of the approach studied.

Physics doi: 10.3390/physics7030042

Authors: Marcos V. S. de Paula Marco A. Damasceno Faustino Alexandre V. Dodonov

We compare the semiclassical and quantum predictions for the unitary dynamics of a two-level atom interacting with a single-mode electromagnetic field under parametric modulation of the atomic parameters in the regime of multiphoton atom–field resonances. We derive approximate analytic solutions for the semiclassical Rabi model when the atomic transition frequency and the atom–field coupling strength undergo harmonic external modulations. These solutions are compared to the predictions of the quantum Rabi model, which we solve numerically for an initial coherent state with a large average photon number (on the order of 104), in the regime of three-photon resonance. We show that, for short enough times and sufficiently intense coherent states, the semiclassical dynamics agrees quite well with the quantum dynamics, although it inevitably fails at longer times due to the absence of collapse–revival behavior. Furthermore, we describe how the field state evolves throughout the interaction, presenting numerical results for the average photon number, entropies (related to atom–field entanglement), and other quantities characterizing the photon number statistics of the electromagnetic field.

Physics doi: 10.3390/physics7030041

Authors: Vyacheslav I. Yukalov Elizaveta P. Yukalova

The paper presents a survey of some dynamical transitions in nonequilibrium trapped Bose-condensed systems subject to the action of alternating fields. Nonequilibrium states of trapped systems can be implemented in two ways: resonant and nonresonant. Under resonant excitation, several coherent modes are generated by external alternating fields with the frequencies been tuned to resonance with some transition frequencies of the trapped system. A Bose system of trapped atoms with Bose–Einstein condensate can display two types of the Josephson effect, the standard one, when the system is separated into two or more parts in different locations, or the internal Josephson effect, when there are no any separation barriers but the system becomes nonuniform due to the coexistence of several coherent modes interacting one with another. The mathematics in both these cases is similar. We focus on the internal Josephson effect. Systems with nonlinear coherent modes demonstrate rich dynamics, including Rabi oscillations, the Josephson effect, and chaotic motion. Under the Josephson effect, there exist dynamic transitions that are similar to phase transitions in equilibrium systems. The bosonic Josephson effect is shown to be implementable not only for quite weakly interacting systems, but also in superfluids with not necessarily as weak interactions. Sufficiently strong nonresonant excitation can generate several types of nonequilibrium states comprising vortex germs, vortex rings, vortex lines, vortex turbulence, droplet turbulence, and wave turbulence. Nonequilibrium states are shown to be characterized and distinguished by effective temperature, effective Fresnel number, and dynamic scaling laws.

Physics doi: 10.3390/physics7030040

Authors: Volodymyr M. Lashkin Oleg K. Cheremnykh

We demonstrate the possibility of generation of zonal (shear) flows in a rotating self-gravitating fluid. A set of equations describing the nonlinear interaction between a large-scale zonal flow (ZF) and a small-scale drift-gravity wave is derived. A nonlinear dispersion relation is obtained, from which the possible instability of the ZF follows. The necessary condition for instability in the space of wave numbers of the drift-gravity wave, as well as the instability threshold for the wave amplitude, are obtained. The growth rate of the modulation instability of ZF is found. The generation of ZFs is due to the Reynolds stresses produced by finite amplitude drift-gravity waves.

Physics doi: 10.3390/physics7030039

Authors: Valeriya Mykhaylova

The production rate of charm quarks in strongly interacting matter is investigated under various conditions, employing the effective quasiparticle framework. This phenomenological approach treats quarks and gluons as quasiparticles with dynamically generated self-energies linked to the medium. This paper studies thermal production of charm quarks in hot deconfined matter when those quarks are treated as impurities with a constant mass or as dynamical quarks dressed by the effective mass. When charm quarks are considered quasiparticles, their large (compared to the bare value) mass generates a significant decrease in the production rate in the crossover region. Various initial conditions for the evolution of the system are applied, showing that lower initial temperature leads to the continual suppression of the charm quark production rate, which appears in line with the previously reported estimate at certain values of the initial parameters.

Physics doi: 10.3390/physics7030038

Authors: Ofir E. Alon Lorenz S. Cederbaum

We consider a multi-species mixture of interacting bosons, N1 bosons of mass m1, N2 bosons of mass m2, and N3 bosons of mass m3, in a harmonic trap with frequency ω. The corresponding intra-species interaction strengths are λ11, λ22, and λ33, and the inter-species interaction strengths are λ12, λ13, and λ23. When the shape of all interactions is harmonic, the system corresponds to the generic multi-species harmonic-interaction model, which is exactly solvable. We start by solving the many-particle Hamiltonian and concisely discussing the ground-state wavefunction and energy in explicit forms as functions of all parameters, the masses, numbers of particles, and the intra-species and inter-species interaction strengths. We then explicitly compute the reduced one-particle density matrices for all the species and diagonalize them, thus generalizing the treatment by the authors earlier. The respective eigenvalues determine the degree of fragmentation of each species. As an application, we focus on phenomena that do not arise in the corresponding single-species or two-species systems. For instance, we consider a mixture of two kinds of bosons in a bath made by a third kind, controlling the fragmentation of the former by coupling to the latter. Another example exploits the possibility of different connectivities (i.e., which species interacts with which species) in the mixture, and demonstrates how the fragmentation of species 3 can be manipulated by the interaction between species 1 and species 2, when species 3 and 1 do not interact with each other. We highlight the properties of fragmentation that only appear in the multi-species mixture. Further applications are briefly discussed.

Physics doi: 10.3390/physics7030037

Authors: Stanisław A. Różański

The Planck constant is a fundamental parameter of nature that appears in the description of phenomena on a microscopic scale. Its origin is associated with an explanation of the distribution of the blackbody spectrum performed by Max Planck. This constant stands the basis for the definition of the International System of Units (SI), and, in particular, the new mass definition. This paper presents different methods for determining the Planck constant based on phenomena such as blackbody radiation, light diffraction through a single slit, the current–voltage characteristics of a light-emitting diode, the photoelectric phenomenon, and the hydrogen atom spectrum in the visible range. The Planck constant was measured using instruments in a stationary laboratory and via remote access. The influence of various factors on the accuracy of the measurements was determined, and the consistency of the obtained results with the accepted value of the Planck constant are examined and discussed.

Physics doi: 10.3390/physics7030036

Authors: Diego Julio Cirilo-Lombardo

A new conformally invariant gravitational generalization of the Born–Infeld (BI) model is proposed and analyzed from the point of view of symmetries. Taking a geometric identity involving the determinant functions detfBμν, Fμν with the Bach Bμν and the electromagnetic field Fμν tensors (with the 4-dimensional Greek letter indexes), two characteristic geometrical Lagrangian densities (Lagrangians) are derived: the first Lagrangian being the square root of the determinant function detBμν+Fμν (reminiscent of the standard BI model) and the second Lagrangian being the fourth root gdetBαγBβγ+FαγFβγ4. It is shown, after explicit computation of the gravitational equations, that the square-root model is incompatible with the inclusion of the electromagnetic tensor, consequently forcing the nullity of Fμν. In sharp contrast, the traceless fourth-root model is fully compatible and a natural ansatz of the type BμρBνρ∝Ωxgμν (conformal-Killing), with Ω the conformal factor and x the 4-coordinate, can be considered. Among other essential properties, the geometrical conformal Lagrangian of the fourth-root type is self-similar with respect to the determinant g of the metric tensor gμν and can be extended to non-Abelian fields in a way similar to the model developed by the author earlier. This self-similarity is related to the conformal properties of the model, such as the Bach currents or flows presumably of a topological origin. Possible applications and comparisons with other models are briefly discussed.

Physics doi: 10.3390/physics7030035

Authors: Alfredo M. Ozorio de Almeida

Semiclassical (SC) approximations for various representations of a quantum state are constructed on a single (Lagrangian) surface in the phase space but such surface is not available for chaotic systems. An analogous evolution surface underlies SC representations of the evolution operator, albeit in a doubled phase space. Here, it is shown that corresponding to the Fourier transform on a unitary operator, represented as a Green function or spectral Wigner function, a Legendre transform generates a resolvent surface as the classical basis for SC representations of the resolvent operator in the double-phase space, independently of the integrable or chaotic nature of the system. This surface coincides with derivatives of action functions (or generating functions) depending on the choice of appropriate coordinates, and its growth departs from the energy shell following trajectories in the double-phase space. In an initial study of the resolvent surface based on its caustics, its complex nature is revealed to be analogous to a multidimensional sponge. Resummation of the trace of the resolvent in terms of linear combinations of periodic orbits, known as pseudo orbits or composite orbits, provides a cutoff to the SC sum at the Heisenberg time. Here, it is shown that the corresponding actions for higher times can be approximately included within true secondary periodic orbits, in which heteroclinic orbits join multiple windings of relatively short periodic orbits into larger circuits.

Physics doi: 10.3390/physics7030034

Authors: Ziheng Li Jiangwei Liu Xiaoxiao Zheng Yu Sun Nan Han Liang Wang Muyang Li Lei Han Safia Khan S. Hassan M. Jafri Klaus Leifer Yafei Ning Hu Li

Herein, the energy dispersion relationship and the density of states of triangular and rectangular moiré patterns are investigated using a tight binding model. Their characteristics of Hofstadter butterflies under different magnetic fields are also examined. The results indicate that, by analyzing different moiré superlattices, Hofstadter butterflies arising from different moiré pattern structures are obtained, exhibiting considerable fractal characteristics and self-similarities. Moreover, it is also observed that under an alternating magnetic field, the redistribution of electronic states leads to a significant change in the density of states curve, and the Van Hove peak changes with the increase in magnetic field intensity. This study enriches the understanding of the electronic behavior of moiré systems, but it also provides multiple potential application directions for future technological development.

Physics doi: 10.3390/physics7030033

Authors: Burak Hacisahinoglu Suat Ozkorucuklu Maksym Ovchynnikov Michael G. Albrow Aldo Penzo Orhan Aydilek

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass or by considerably small coupling to SM particles. The latter case implies relatively long lifetimes. Such long-lived particles (LLPs) then to have signatures different from those of SM particles. Searches in the “central region” are covered by the LHC general purpose experiments. The forward small angle region far from the interaction point (IP) is unexplored. Such particles are expected to have the energy as large as E = O(1 TeV) and Lorentz time dilation factor γ=E/m≈102–103 (with m the particle mass) hence long enough decay distances. A new class of specialized LHC detectors dedicated to LLP searches has been proposed for the forward regions. Among these experiments, FASER is already operational, and FACET is under consideration at a location 100 m from the LHC IP5 (the CMS detector intersection). However, some features of FACET require a specially enlarged beam pipe, which cannot be implemented for LHC Run 4. In this study, we explore a simplified version of the proposed detector PREFACE compatible with the standard LHC beam pipe in the HL-LHC Run 4. Realistic Geant4 simulations are performed and the background is evaluated. An initial analysis of the physics potential with the PREFACE geometry indicates that several significant channels could be accessible with sensitivities comparable to FACET and other LLP searches.

Physics doi: 10.3390/physics7030032

Authors: Haotian Chen Shifeng Mao Zejun Ding

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield is almost equivalent to the case when the electron flow is not considered. The electron yields and charging spatial distribution are obtained. For comparison, the calculation for bulk conductor is also performed, for which the time average of electric potential is found to reproduce the law of electrostatics.

Physics doi: 10.3390/physics7030031

Authors: Zbigniew Drogosz

The paper outlines the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel–Stewart method of introducing dissipation. The local equilibrium expressions for the baryon current, the energy–momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi–Dirac statistics are obtained and compared with the earlier derived versions where the Boltzmann approximation was used. The expressions in the two cases are found to have the same form, but the coefficients are shown to be governed by different functions. The relative differences between the tensor coefficients in the Fermi–Dirac and Boltzmann cases are found to grow exponentially with the baryon chemical potential. In the proposed formalism, nonequilibrium processes are studied including mathematically possible dissipative corrections. Standard conservation laws are applied, and the condition of positive entropy production is shown to allow for the transfer between the spin and orbital parts of angular momentum.

Physics doi: 10.3390/physics7030030

Authors: Emanuela Musumeci Adrián Irles Redamy Pérez-Ramos Imanol Corredoira Edward Sarkisyan-Grinbaum Vasiliki A. Mitsou Miguel Ángel Sanchis-Lozano

Future e+e− colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions is considered to be a hint for new physics perturbing the QCD partonic cascade and thereby modifying azimuthal and (pseudo)rapidity correlations. Using Pythia8 Monte Carlo generator and fast simulation, including selection cuts and detector effects, we study potential structures in the two-particle angular correlation function. We adopt the QCD-like Hidden Valley (HV) scenario as implemented in Pythia8 generator, with relatively light HV v-quarks (below about 100 GeV), to illustrate the potential of this method.

Physics doi: 10.3390/physics7030029

Authors: Aek Jantayod

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute the particle transport characteristics in the junction, taking into consideration the interface quality. It is found that the spin polarization becomes strongly reliant on the spin-flip scattering potential at applied voltages close to the crossings of the semiconductor-based RSOI band. On the other hand, in the voltage near the middle band, the spin polarization of current is found to remain modest and not influenced by either the spin-flip or non-spin-flip scattering potentials.

Physics doi: 10.3390/physics7030028

Authors: Pazhani Durgadevi Koyeli Girigoswami Agnishwar Girigoswami

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of hope in the fight against MDR microorganisms. Among the natural photosensitizers, hypocrellins (A and B) have shown remarkable potential with their dual-mode photodynamic action, generating ROS via both Type I (electron transfer) and Type II (singlet oxygen) pathways. This unique action disrupts bacterial biofilms and inactivates MDR pathogens. The amphiphilic nature of hypocrellins further enhances their promise, enabling deep biofilm penetration and ensuring potent antibacterial effects even in hypoxic environments, surpassing the capabilities of synthetic photosensitizers. This study critically examines the antimicrobial properties of hypocrellin-based PDT, emphasizing its mechanisms, advantages over traditional antibiotics, and effectiveness against MDR pathogens. Comparative analysis with other photosensitizers, the role of nanotechnology-enhanced delivery systems, and future clinical applications are explored. Its combination with nanotechnology enhances therapeutic outcomes, providing a viable alternative to conventional antibiotics. Further clinical research is essential to optimize its application and integration into antimicrobial treatment protocols.

Physics doi: 10.3390/physics7030027

Authors: Ali Farooq Wen Xu Jie Zhang Hua Wen Qiujin Wang Xingjia Cheng Yiming Xiao Lan Ding Altayeb Alshiply Abdalfrag Hamdalnile Haowen Li Francois M. Peeters

Monolayer (ML) molybdenum disulfide (MoS2) is a typical valleytronic material which has important applications in, for example, polarization optics and information technology. In this study, we examine the effect of continuous wave (CW) laser pumping on the basic optoelectronic properties of ML MoS2 placed on a sapphire substrate, where the pump photon energy is larger than the bandgap of ML MoS2. The pump laser source is provided by a compact semiconductor laser with a 445 nm wavelength. Through the measurement of THz time-domain spectroscopy, we obtain the complex optical conductivity for ML MoS2, which are found to be fitted exceptionally well with the Drude–Smith formula. Therefore, we expect that the reduction in conductivity in ML MoS2 is mainly due to the effect of electronic backscattering or localization in the presence of the substrate. Meanwhile, one can optically determine the key electronic parameters of ML MoS2, such as the electron density ne, the intra-band electronic relaxation time τ, and the photon-induced electronic localization factor c. The dependence of these parameters upon CW laser pump intensity is examined here at room temperature. We find that 445 nm CW laser pumping results in the larger ne, shorter τ, and stronger c in ML MoS2 indicating that laser excitation has a significant impact on the optoelectronic properties of ML MoS2. The origin of the effects obtained is analyzed on the basis of solid-state optics. This study provides a unique and tractable technique for investigating photo-excited carriers in ML MoS2.

Physics doi: 10.3390/physics7030026

Authors: Carmen Toro-Castillo Joel Cervantes-Lozano David I. Serrano-García Héctor O. González-Ochoa

The one-dimensional ray equation, the differential description of Fermat’s principle, is deduced directly from Snell’s law using two methods. In the first method, we obtain the ray equation from a differential equation relating the spatial coordinates derivative with the index of refraction field. In the second method, the ray equation is deduced from the proper generalization of Snell’s law for a refractive field, that is, a differential equation relating the index of refraction field and the refraction angle. Additionally, we used an intermediate expression of the first method to find a straightforward analytical solution of the ray path to an inferior mirage.

Physics doi: 10.3390/physics7030025

Authors: Rafael M. Fortiny Matheus E. Pereira Alexandre G. M. Schmidt

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple slits and by a Cantor set. We present detailed calculations of the scattered wave function for the line segment, as well as for the single, double, and multiple slits. We define reflection and transmission functions that are position-dependent in a defined region. From these results, we obtain the probability densities and differential and total cross-sections for these problems.

Physics doi: 10.3390/physics7030024

Authors: Daniel Almeida Fagundes Magno V. T. Machado

In this paper, we analyze the application of an analytical gluon distribution based on double-asymptotic scaling to the photoproduction of vector mesons in coherent pp, pA, and AA collisions at LHC energies, using the color dipole formalism. Predictions for the rapidity distribution are presented for ρ0, J/ψ, ψ(2S), and Υ(1S) mesons photoproduction. An analysis of the uncertainties associated with different implementations of the dipole–proton amplitude is performed. The vector meson photoproduction accompanied by electromagnetic dissociation is also analyzed.

Physics doi: 10.3390/physics7020023

Authors: Jan Stenflo

The large-scale dynamics of the universe is generally described in terms of the time-dependent scale factor a(t). To make contact with observational data, the a(t) function needs to be related to the observable z(r) function, redshift versus distance. Model fitting of data has shown that the equation that governs z(r) needs to contain a constant term, which has been identified as Einstein’s cosmological constant. Here, it is shown that the required constant term is not a cosmological constant but is due to an overlooked geometric difference between proper time t and look-back time tlb along lines of sight, which fan out isotropically in all directions of the 3D (3-dimensional) space that constitutes the observable universe. The constant term is needed to satisfy the requirement of spatial isotropy in the local limit. Its magnitude is independent of the epoch in which the observer lives and agrees with the value found by model fitting of observational data. Two of the observational consequences of this explanation are examined: an increase in the age of the universe from 13.8 Gyr to 15.4 Gyr, and a resolution of the H0 tension, which restores consistency to cosmological theory.

Physics doi: 10.3390/physics7020022

Authors: Carlos Alberto Dagua-Conda John Alexander Gil-Corrales Rebeca Victoria Herrero-Hahn Miguel Eduardo Mora-Ramos Alvaro Luis Morales Carlos Alberto Duque

External fields modify the confinement potential and electronic structure in a multiple quantum well system, affecting the light–matter interaction. Here, we present a theoretical study of the modulation of the nonlinear optical response simultaneously employing an intense non-resonant laser field and an electric field. Considering four occupied subbands, we focus on a GaAs/AlGaAs symmetric multiple quantum well system with five wells and six barriers. By solving the Schrödinger equation through the finite element method under the effective mass approximation, we determine the electronic structure and the nonlinear optical response using the density matrix formalism. The laser field dresses the confinement potential while the electric field breaks the inversion symmetry. The combined effect of both fields modifies the intersubband transition energies and the overlap of the wave functions. The results obtained demonstrate an active tunability of the nonlinear optical response, opening up the possibility of designing optoelectronic devices with tunable optical properties.

Physics doi: 10.3390/physics7020021

Authors: Kewen Jing Haitao Li Henggao Xiang Xianghe Peng

The macroscopic magnetic properties of magnetorheological elastomers (MREs) are influenced by their microstructure, yet limited investigations has been conducted on this subject to date. In this paper, a microstructure-based model is proposed to investigate the magnetization response of MREs. The dipole theory is employed to compute the local magnetic field, and a fitting equation derived from finite element analysis is used to correct the magnetic field. The Fröhlich–Kennelly equation is applied to describe the nonlinear magnetic properties of the particle material. Based on experimental observations, a body-centered tetragonal (BCT) model is established to describe the magnetization properties of anisotropic MREs. The proposed model is validated by comparison with experimental data and can be utilized to predict the effective susceptibility of MREs. The effects of particle volume fraction, the direction of the external magnetic field, and the shape of the MRE samples can also be analyzed using this model.

Physics doi: 10.3390/physics7020020

Authors: Roberto Passante Lucia Rizzuto

We consider a multilevel atom, such as a hydrogen atom, interacting with the quantum electromagnetic field in the dressed ground state of the interacting system. Using perturbation theory within the dipole approximation, we evaluate the dressed ground state and investigate the effect of atomic self-dressing on several field and atomic observables. Specifically, we obtain general expressions of the renormalized electric and magnetic field fluctuations and energy densities around the atom, and analyze their scaling with the distance from the atom, obtaining approximated expressions in the so-called near and far zones. We also investigate nonlocal spatial field correlations around the atom. We stress how the quantities we evaluate can be probed through two- and three-body nonadditive Casimir–Polder dispersion interactions. We also investigate the effect of self-dressing—namely, the virtual transitions occurring in the dressed ground state—on atomic observables, such as the average potential energy of the electron in the nuclear field. This also allows us to obtain a more fundamental quantum basis for the Welton interpretation of the Lamb shift of a ground-state hydrogen atom, in terms of the atomic self-dressing processes.

Physics doi: 10.3390/physics7020019

Authors: Nathan A. Lanfear Sergei K. Suslov

We construct the Green functions (or Feynman’s propagators) for the Schrödinger equations of the form iψt+14ψxx±tx2ψ=0 (for the wave function ψ and its time (t) and x-space derivatives) in terms of Airy functions and solve the Cauchy initial value problem in the coordinate and momentum representations. Particular solutions of the corresponding nonlinear Schrödinger equations with variable coefficients are also found. A special case of the quantum parametric oscillator is studied in detail first. The Green function is explicitly given in terms of Airy functions and the corresponding transition amplitudes are found in terms of a hypergeometric function. The general case of the quantum parametric oscillator is considered then in a similar fashion. A group theoretical meaning of the transition amplitudes and their relation with Bargmann’s functions is established. The relevant bibliography, to the best of our knowledge, is addressed.

Physics doi: 10.3390/physics7020018

Authors: Qinrui Chen Liangqiang Zhou Fengxian An

In this paper, the chaotic behavior and subharmonic bifurcation in a dynamical model for charged dilation-AdS black holes are investigated in extended phase space using analytical and numerical methods. An analytical expression for the chaotic critical value at the disturbance amplitude is obtained using the Melnikov method, revealing the monotonicity of the threshold values for chaos with charge and frequency, and the coupling parameters between the expansion field and the Maxwell field are studied. It is shown that chaos can be controlled through the system parameters. Meanwhile, an analytical expression for the critical value of the bifurcation of subharmonic orbits at disturbance amplitudes is acquired using the subharmonic Melnikov method. The relationship between the threshold value and the vibration frequency and the order of the subharmonic orbit is studied. This demonstrates that the system undergoes chaotic motion via infinite odd-order subharmonic bifurcations. Finally, numerical simulations are used to verify the analytical results.

Physics doi: 10.3390/physics7020017

Authors: Ilias Benyahia Aissa Abderrahmane Yacine Khetib Mashhour A. Alazwari Obai Younis Abdeldjalil Belazreg Samir Laouedj

Phase change materials (PCMs) are widely used in latent heat thermal energy storage systems (LHTESSs), but their low thermal conductivity limits performance. This study numerically investigates the enhancement of thermal efficiency in LHTESSs using nano-enhanced PCM (NePCM), composed of paraffin wax embedded with copper (Cu) nanoparticles. The NePCM is confined within a trapezoidal cavity, with the base serving as the heat source. Four different cavity heights were analyzed: cases 1, 2, 3, and 4 with the heights D of 24 mm, 18 mm, 15 mm, and 13.5 mm, respectively. The finite element method was employed to solve the governing equations. The influence of two hot base temperatures (333.15 K and 338.15 K) and Cu nanoparticle volume fractions ranging from 0% to 6% was examined. The results show that incorporating Cu nanoparticles at 6 vol% (volume fraction) enhanced thermal conductivity and reduced melting time by 10.71%. Increasing the base temperature to 338.15 K accelerated melting by 65.55%. Among all configurations, case 4 exhibited the best performance, reducing melting duration by 15.12% compared to case 1.

Physics doi: 10.3390/physics7020016

Authors: Oleg M. Gradov

In this paper, an equation describing nonlinear wave phenomena on the surface of magnetically active plasma in the approximation of the complete homogeneity of processes along the direction of the constant magnetic field is obtained. One of its solutions, in the form of a pulse having the shape of rapidly decaying oscillations with a changing period, is found to essentially depend on the magnitude of the magnetic field and shown to be approximately described by a specially selected analytical function. A detailed analytical analysis of the properties of another solitary wave formation existing under conditions of resonant coincidence of its carrier frequency with the corresponding value of its eigen surface oscillations in the considered cold semi-infinite plasma, in which a constant magnetic field is directed along its boundary, is also carried out. The conditions for the excitation of wave disturbances are determined, and analytical expressions that adequately describe the space–time structure of nonlinear waves are proposed.

Physics doi: 10.3390/physics7020015

Authors: Annu Choudhary Vinod Kumar Amritanshu Shukla

The shape parameters and energy spectra of the decoupled h11/2 bands in isotopes Ru99,101,103, 101,103,105,107Pd and 101,103,105,107Cd are analyzed using the particle-plus-rotor model and cranked shell model calculations. The quasiparticle-plus-rotor (PRM) model calculations are performed, considering both soft and rigid triaxial cores, using the constant-moment-of-inertia (CMI) and variable-moment-of-inertia (VMI) approaches. The asymmetry parameter γ obtained from the PRM model calculations is found to be consistent with the results obtained from the cranked shell model calculations when the core exhibited CMI behavior.

Physics doi: 10.3390/physics7020014

Authors: Suryadi Precious O. Amadi Norshamsuri Ali

This study presents a theoretical investigation into the interference properties of three photons in a six-port optical beam splitter, commonly referred to as a tritter. We examine various configurations of the relative phase differences among the input photons. Our findings reveal that fully constructive interference periodically occurs at a single output port for specific constant phase differences, while fully destructive interference simultaneously manifests at the remaining two output ports. These distinctive interference patterns arise across a wide range of specific phase difference combinations among the input photons. We suggest that these unique interference characteristics provide new insights into the potential implementation of a three-party quantum key distribution protocol. Such three-photon interference phenomena are crucial for facilitating symmetric secure key distribution among three parties.