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Physics, Volume 8, Issue 1 (March 2026) – 32 articles

Cover Story (view full-size image): This study investigated 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 the establishment of a significant cross-correlation between NEs, so that their internal dynamics depend on the NR's plasma frequency. The chimera-like state is realized in such hybrid medium as the coexistence of locally synchronized and desynchronized NE dynamical states. View this paper
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18 pages, 492 KB  
Article
Condensate Dark Stars Beyond the Mean-Field Approximation: The Lee–Huang–Yang Correction
by Grigoris Panotopoulos
Physics 2026, 8(1), 32; https://doi.org/10.3390/physics8010032 - 10 Mar 2026
Viewed by 538
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology: 2nd Edition)
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21 pages, 349 KB  
Article
Quantum Concepts and Techniques in Classical Domains Demonstrated in Bulk Phonons and Plasmons
by Mohamed Babiker
Physics 2026, 8(1), 31; https://doi.org/10.3390/physics8010031 - 3 Mar 2026
Viewed by 678
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Quantum Theory 100 Years Later: Advances on Foundations and Applications)
21 pages, 436 KB  
Article
Mean Extinction Times in Multi-Metastable Systems: A Discrete Coarse-Grained Approach
by Santosh Kumar Kudtarkar
Physics 2026, 8(1), 30; https://doi.org/10.3390/physics8010030 - 2 Mar 2026
Viewed by 371
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Statistical Physics and Nonlinear Phenomena)
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11 pages, 255 KB  
Article
Dark Energy from Entanglements with Mirror Universe
by Merab Gogberashvili and Tinatin Tsiskaridze
Physics 2026, 8(1), 29; https://doi.org/10.3390/physics8010029 - 2 Mar 2026
Cited by 1 | Viewed by 726
Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology: 2nd Edition)
16 pages, 328 KB  
Article
Linear Instability of Three-Dimensional Dynamic Equilibrium States for Two-Component Vlasov–Poisson Plasma
by Yuriy G. Gubarev and Jingyue Luo
Physics 2026, 8(1), 28; https://doi.org/10.3390/physics8010028 - 2 Mar 2026
Viewed by 372
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Condensed Matter Physics)
13 pages, 1152 KB  
Article
Influence of Three-Body Recombination on Formation of Dark Atoms
by Dmitry Kalashnikov and Konstantin Belotsky
Physics 2026, 8(1), 27; https://doi.org/10.3390/physics8010027 - 2 Mar 2026
Viewed by 554
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology: 2nd Edition)
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18 pages, 1864 KB  
Review
Primer of Strong-Field Quantum Electrodynamics for Experimentalists
by Annabel Kropf and Ivo Schulthess
Physics 2026, 8(1), 26; https://doi.org/10.3390/physics8010026 - 2 Mar 2026
Cited by 2 | Viewed by 1060
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section High Energy Physics)
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15 pages, 977 KB  
Article
Particle-in-Cell Simulations of Laser Crossbeam Energy Transfer via Magnetized Ion-Acoustic Wave
by Yuan Shi and John D. Moody
Physics 2026, 8(1), 25; https://doi.org/10.3390/physics8010025 - 1 Mar 2026
Viewed by 514
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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17 pages, 986 KB  
Article
Interacting Ricci-Type Holographic Dark Energy and Dark Sector Couplings
by 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 and Antonio Rivasplata-Mendoza
Physics 2026, 8(1), 24; https://doi.org/10.3390/physics8010024 - 1 Mar 2026
Viewed by 627
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology: 2nd Edition)
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22 pages, 875 KB  
Article
Hamiltonian Dynamics of Classical Spins
by Slobodan Radošević, Sonja Gombar, Milica Rutonjski, Petar Mali, Milan Pantić and Milica Pavkov-Hrvojević
Physics 2026, 8(1), 23; https://doi.org/10.3390/physics8010023 - 25 Feb 2026
Viewed by 763
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Physics Education)
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13 pages, 1339 KB  
Article
Kicked Fluxonium with a Quantum Strange Attractor
by Alexei D. Chepelianskii and Dima L. Shepelyansky
Physics 2026, 8(1), 22; https://doi.org/10.3390/physics8010022 - 16 Feb 2026
Viewed by 594
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Quantum Mechanics and Quantum Systems)
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15 pages, 1756 KB  
Article
Dynamical Correlations and Chimera-like States of Nanoemitters Coupled to Plasmon Polaritons in a Lattice of Conducting Nanorings
by Boris A. Malomed, Gennadiy Burlak, Gustavo Medina-Ángel and Yuri Karlovich
Physics 2026, 8(1), 21; https://doi.org/10.3390/physics8010021 - 16 Feb 2026
Viewed by 474
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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62 pages, 1346 KB  
Review
Non-Relativistic Quantum Electrodynamics and the Coulomb Interaction
by R. Guy Woolley
Physics 2026, 8(1), 20; https://doi.org/10.3390/physics8010020 - 12 Feb 2026
Viewed by 913
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Quantum Theory 100 Years Later: Advances on Foundations and Applications)
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19 pages, 954 KB  
Article
Quantum Theory and Unusual Dielectric Functions of Graphene
by Vladimir M. Mostepanenko and Galina L. Klimchitskaya
Physics 2026, 8(1), 19; https://doi.org/10.3390/physics8010019 - 10 Feb 2026
Viewed by 552
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Quantum Theory 100 Years Later: Advances on Foundations and Applications)
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14 pages, 1677 KB  
Review
Partially Ionized Plasma Physics and Technological Applications
by Igor Kaganovich and Michael Tendler
Physics 2026, 8(1), 18; https://doi.org/10.3390/physics8010018 - 6 Feb 2026
Viewed by 1015
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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17 pages, 601 KB  
Article
Exact Solutions to a Model for Micropolar Fluid Flows with Rayleigh Energy Dissipation
by Evgenii Yu. Prosviryakov, Evgenii S. Baranovskii, Sergey V. Ershkov and Alexander V. Yudin
Physics 2026, 8(1), 17; https://doi.org/10.3390/physics8010017 - 6 Feb 2026
Viewed by 421
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Classical Physics)
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10 pages, 4014 KB  
Communication
Wave-Packet Transport in Graphene Under Asymmetric Electrostatic Arrays: Geometry-Tunable Confinement
by Khakimjan Butanov, Maksudbek Baydjanov, Hammid Yusupov, Komiljon Bobojonov, Maksudbek Yusupov, Andrey Chaves and Khamdam Rakhimov
Physics 2026, 8(1), 16; https://doi.org/10.3390/physics8010016 - 6 Feb 2026
Viewed by 574
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Condensed Matter Physics)
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11 pages, 396 KB  
Article
Kinetic Theory of Solitons and Quasi-Particles
by José Tito Mendonça and Kyriakos Hizanidis
Physics 2026, 8(1), 15; https://doi.org/10.3390/physics8010015 - 5 Feb 2026
Viewed by 634
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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12 pages, 14633 KB  
Article
Internal Gravity Wave Turbulence in the Earth’s Ionospheric F-Layer
by Sukhendu Das Adhikary and Amar Prasad Misra
Physics 2026, 8(1), 14; https://doi.org/10.3390/physics8010014 - 1 Feb 2026
Viewed by 415
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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21 pages, 1086 KB  
Review
On the Possibility of a Dual Cascade in Three-Dimensional Incompressible Turbulent Flows
by Mitsuo Kono and Hans L. Pécseli
Physics 2026, 8(1), 13; https://doi.org/10.3390/physics8010013 - 28 Jan 2026
Viewed by 442
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
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13 pages, 324 KB  
Article
On the Description of Turbulent Transport in Magnetic Confinement Systems
by Jan Weiland and Tariq Rafiq
Physics 2026, 8(1), 12; https://doi.org/10.3390/physics8010012 - 27 Jan 2026
Viewed by 554
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)
10 pages, 275 KB  
Communication
High-Temperature Plasma in Casimir Physics
by Suman Kumar Panja and Mathias Boström
Physics 2026, 8(1), 11; https://doi.org/10.3390/physics8010011 - 20 Jan 2026
Viewed by 767
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Quantum Theory 100 Years Later: Advances on Foundations and Applications)
16 pages, 3266 KB  
Article
Selenium Quantification in Soil by LIBS
by Alexandra V. Rogachevskaya, Vasily N. Lednev, Pavel A. Sdvizhenskii, Igor Y. Savin, Sergey V. Gudkov, Alexey S. Dorohov and Andrey Y. Izmaylov
Physics 2026, 8(1), 9; https://doi.org/10.3390/physics8010009 - 16 Jan 2026
Viewed by 782
Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Section Applied Physics)
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12 pages, 317 KB  
Article
Shortcuts to Adiabaticity, Unexciting Backgrounds, and Reflectionless Potentials
by Fernando C. Lombardo and Francisco D. Mazzitelli
Physics 2026, 8(1), 10; https://doi.org/10.3390/physics8010010 - 16 Jan 2026
Viewed by 661
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)
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19 pages, 1436 KB  
Article
The Geometry of Qubit Decoherence: Linear Versus Nonlinear Dynamics in the Bloch Ball
by Alan C. Maioli, Evaldo M. F. Curado, Jean-Pierre Gazeau and Tomoi Koide
Physics 2026, 8(1), 8; https://doi.org/10.3390/physics8010008 - 14 Jan 2026
Viewed by 663
Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)
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15 pages, 877 KB  
Article
Modeling the Fall of the Inca Empire: A Lotka–Volterra Approach to the Spanish Conquest
by Nuno Crokidakis
Physics 2026, 8(1), 7; https://doi.org/10.3390/physics8010007 - 14 Jan 2026
Cited by 1 | Viewed by 1384
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Statistical Physics and Nonlinear Phenomena)
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13 pages, 5762 KB  
Article
Mechanisms in Droplet Impact on Rough Surfaces with Spontaneously Varying Viscosity
by Shuwen Cao, Jinhong Yang and Shun Lei
Physics 2026, 8(1), 6; https://doi.org/10.3390/physics8010006 - 13 Jan 2026
Viewed by 665
Abstract
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. [...] Read more.
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. Full article
(This article belongs to the Section Classical Physics)
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15 pages, 2275 KB  
Article
Electron Scattering Properties in Dense Quantum Plasma of Neon
by Erik O. Shalenov, Yerkhan A. Tashkenbayev, Yeldos S. Seitkozhanov and Karlygash N. Dzhumagulova
Physics 2026, 8(1), 5; https://doi.org/10.3390/physics8010005 - 1 Jan 2026
Viewed by 776
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Atomic Physics)
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18 pages, 7188 KB  
Article
Predicting Energy-Dependent Transformation Products of Environmental Contaminants: The Case of Ibuprofen
by Grégoire Salomon, Mathias Rapacioli, J. Christian Schön and Nathalie Tarrat
Physics 2026, 8(1), 4; https://doi.org/10.3390/physics8010004 - 30 Dec 2025
Viewed by 482
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Applied Physics)
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16 pages, 7514 KB  
Article
Simulating Magnetic Ordering and Exchange Interactions in Ni2Co(BO3)2
by Svetlana Sofronova, Artem Chernyshev, Anna Selyanina, Aleksandr Krylov and Timofey Tislenko
Physics 2026, 8(1), 3; https://doi.org/10.3390/physics8010003 - 30 Dec 2025
Viewed by 561
Abstract
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%). [...] Read more.
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. Full article
(This article belongs to the Section Condensed Matter Physics)
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