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Concept of UCN Source at WWR-K Reactor (AlSUN)
Mapping OAM-Free Laguerre–Gaussian Astigmatic Beams onto the Poincaré Sphere and Geometric Phases
A Review of Whistler Wave Propagation and Interaction Experiments at Arecibo Observatory, Puerto Rico
Nonlinear Dynamics of Cylindrical Waves in Isentropic Plasma
The Influence of the Inelastic Electron–Phonon Collision Time on the Resistive State of 3D Superconducting Materials

Journal Description

Physics

Physics is an international, peer-reviewed, open access journal which presents latest researches on all aspects of physics. It publishes original research articles, review articles, communications with no restriction on the length of the papers. Physics is published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, ESCI (Web of Science), Inspec, INSPIRE, Astrophysics Data System, and other databases.
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 37.8 days after submission; acceptance to publication is undertaken in 34.2 days (median values for papers published in this journal in the second half of 2025).
Journal Rank: JCR - Q2 (Physics, Multidisciplinary) / CiteScore - Q2 (General Physics and Astronomy)
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Physics.
Journal Cluster of Atomic, Molecular, and Optical (AMO) Physics: Entropy, Photonics, Atoms, Lights, Optics, Plasma, Physics, Quantum Beam Science and Lasers.

Impact Factor: 1.8 (2024); 5-Year Impact Factor: 1.6 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2624-8174

Latest Articles

7 pages, 411 KB

Open AccessCommunication

A Simple Introduction to Gravitomagnetic Effects

by Elmo Benedetto

Physics 2026, 8(2), 42; https://doi.org/10.3390/physics8020042 - 1 May 2026

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 [...] Read more.

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. Full article

(This article belongs to the Section Physics Education)

13 pages, 476 KB

Open AccessArticle

Albedo-Induced Perturbation in the Sitnikov Three-Body Problem

by M. Shahbaz Ullah, M. Javed Idrisi and Sergey Ershkov

Physics 2026, 8(2), 41; https://doi.org/10.3390/physics8020041 - 13 Apr 2026

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 [...] Read more.

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. Full article

(This article belongs to the Section Mathematical Physics and Mathematical Methods)

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16 pages, 6395 KB

Open AccessReview

Casimir Effect with Dielectric Matter in Salted Water and Implications at the Cell Scale

by Larissa Inácio, Felipe S. S. Rosa, Astrid Lambrecht, Paulo A. Maia Neto and Serge Reynaud

Physics 2026, 8(2), 40; https://doi.org/10.3390/physics8020040 - 10 Apr 2026

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 [...] Read more.

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. 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, 1610 KB

Open AccessArticle

First- and Second-Order Raman Scattering and Photorefraction in Nonlinear Optical Crystal LiNbO₃:Y³⁺(0.46 wt%)

by Nikolay V. Sidorov, Mikhail N. Palatnikov, Alexander Y. Pyatyshev and Alexander V. Skrabatun

Physics 2026, 8(2), 39; https://doi.org/10.3390/physics8020039 - 9 Apr 2026

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 [...] Read more.

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. Full article

(This article belongs to the Section Condensed Matter Physics)

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16 pages, 597 KB

Open AccessCommunication

The Influence of a Magnetic Field on Wave Processes in a Viscous Conductive Liquid on a Rotating Wall

by Anatoly A. Gurchenkov and Ivan A. Matveev

Physics 2026, 8(2), 38; https://doi.org/10.3390/physics8020038 - 8 Apr 2026

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 [...] Read more.

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. Full article

(This article belongs to the Section Classical Physics)

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34 pages, 5761 KB

Open AccessArticle

Wigner Quasiprobability of Coherent Phase States

by Alfred Wünsche

Physics 2026, 8(2), 37; https://doi.org/10.3390/physics8020037 - 8 Apr 2026

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 [...] Read more.

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

s u (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

| e^{i φ} ⟩

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. 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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12 pages, 1563 KB

Open AccessArticle

Controlling Magnetic Energy Confinement in One- and Three-Dimensional Systems

by José Holanda

Physics 2026, 8(2), 36; https://doi.org/10.3390/physics8020036 - 3 Apr 2026

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 [...] Read more.

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. Full article

(This article belongs to the Section Applied Physics)

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14 pages, 319 KB

Open AccessArticle

Non-Commutative Integration Method and Generalized Coherent States

by Alexander Breev and Dmitry Gitman

Physics 2026, 8(2), 35; https://doi.org/10.3390/physics8020035 - 2 Apr 2026

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)

10 pages, 279 KB

Open AccessArticle

A Scalar Particle Under Effects of a Magnetic Field Induced by the Lorentz Symmetry Violation

by Fernando M. O. Moucherek and Ricardo L. L. Vitória

Physics 2026, 8(2), 34; https://doi.org/10.3390/physics8020034 - 2 Apr 2026

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. [...] Read more.

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. Full article

(This article belongs to the Section High Energy Physics)

23 pages, 590 KB

Open AccessArticle

Why the Casimir Force for Magnetic Metals Computed by the Lifshitz Theory Using the Drude Model Disagrees with the Measurement Data

by Galina L. Klimchitskaya, Constantine C. Korikov and Vladimir M. Mostepanenko

Physics 2026, 8(2), 33; https://doi.org/10.3390/physics8020033 - 1 Apr 2026

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 [...] Read more.

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

μ

m, 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. Full article

(This article belongs to the Special Issue Quantum Theory 100 Years Later: Advances on Foundations and Applications)

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18 pages, 492 KB

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

As is known, the standard cosmological model (

Λ

CDM ) 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 (

Λ

CDM ) 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

Λ

CDM 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

Open AccessReview

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Λ

CDM (

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

Open AccessArticle

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

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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