Physics

We consider the Casimir pressure between two metallic plates and calculate the four contributions to it determined by the propagating and evanescent waves and by the transverse magnetic and transverse electric polarizations of the electromagnetic field. The range of interplate separations is considered where nearly the whole pressure has its origin in the electromagnetic response of conduction electrons. In the Casimir physics, this response is described either by the dissipative Drude model resulting in contradictions with the measurement data or by the experimentally consistent but dissipationless plasma model. It is shown that the total transverse magnetic contribution to the Casimir pressure due to both the propagating and evanescent waves and the transverse electric contribution due to only the propagating waves, computed by means of the Drude model, correlate well with the corresponding results obtained using the plasma model. We conclude that the disagreement between the theoretical predictions obtained using the Drude model and precision measurements of the Casimir force is not caused by the account of dissipation in itself, but arises from an incorrect description of the response of metals to the low-frequency transverse electric evanescent waves by this model. It is demonstrated that the Drude model has no supporting experimental evidence in the range of transverse electric evanescent waves, so that the above conclusion is consistent with all available information. The alternative test of the Drude model for the transverse electric evanescent waves suggested in the framework of classical electrodynamics is discussed. Full article

The focus of this paper is on analyzing the role and the choice of parameters in sociophysics diffusion models by leveraging the potentialities of sociophysics from a mathematical programming perspective. We first present a generalised version of Galam’s opinion diffusion model. For a given selection of the coefficients in our model, this proposal yields the original Galam’s model. The generalised model suggests guidelines for possible alternative selection of its parameters that allow it to foster diffusion. Examples of the parameters selection process as steered by numerical optimisation, taking into account various objectives, are provided. Full article

Graphene exhibits diamagnetism, enabling it to be lifted by the repulsive force produced in an inhomogeneous magnetic field. However, the stable levitation of a graphene flake perpendicular to the magnetic field is impeded by its strong anisotropic of magnetic susceptibility that induces rotation. A method to suppress this rotation by applying the Casimir force to the graphene flake is presented in this paper. As a result, the graphene flake can archive stable levitation on a silicon plate when the gravitational force is small. Full article

We study the Galam’s majority-rule model in the presence of an independent behavior that can be driven intrinsically or can be mediated by information regarding the collective opinion of the whole population. We first apply the mean-field approach where we obtained an explicit time-dependent solution for the order parameter of the model. We complement our results with Monte Carlo simulations where our findings indicate that independent opinion leads to order–disorder continuous nonequilibrium phase transitions. Finite-size scaling analysis show that the model belongs to the mean-field Ising model universality class. Moreover, results from an approach with the Kramers–Moyal coefficients provide insights about the social volatility. Full article

Solar cosmic rays (SCRs) are generated during the primordial energy release in solar flares. This explosive process takes place in the solar corona above the active region. It represents the fast release of the magnetic field energy of the current sheet, which is formed near a singular magnetic field line. Solar cosmic rays appear as a result of the acceleration of charged particles, mainly protons, by an inductive electric field in the current sheet equal to the field E = V × B/c (with V the speed of plasma and B the magnetic field near the current sheet, and c the speed of light). To study the mechanism of solar flares and obtain conditions for studying SCR acceleration, it is necessary to carry out magnetohydrodynamic (MHD) simulations of flare situations in the solar corona above a real active region. Methods of stabilization were developed which made it possible to partially solve the problem of numerical instabilities. MHD simulations shows complicated configurations near the singular line. Comparison of the results of the MHD simulations with observations showed the general agreement of the positions of the current sheets with regions of intense flare radiation. However, there are some problems with the details of such coincidences. The results obtained in this paper show the possibility of improving the methods of MHD simulation in order to solve the problems that arise during solving of MHD equations. Full article

The Lamb shift, one of the most fundamental interactions in atomic physics, arises from the interaction of H atoms with the electromagnetic fluctuations of the quantum vacuum. The energy shift has been computed in a variety of ways. The energy shift, as Feynman, Power, and Milonni demonstrated, equals the change in the vacuum energy in the volume containing the H atoms due to the change in the index of refraction arising from the presence of the H atoms. Using this result and a group theoretical calculation of the contribution to the Lamb shift from each frequency of the vacuum fluctuations, in this paper we obtain an expression for the region of the vacuum energy for each frequency $\omega$ around the H atom due to the Lamb shift. This same field plays an essential role in the van der Waals force. We show the ground state atom is surrounded by a region of positive vacuum energy that extends well beyond the atom for low frequencies. This region can be described as a steady state cloud of vacuum fluctuations. For energies $E=\hslash \omega$ less than 1 eV, where ℏ is the reduced Planck constant and $\omega$ is frequency, the radius of the positive energy region is shown to be approximately 14.4/E Å. For a vacuum fluctuation of wavelength, $\lambda$, the radius is $(\alpha /2\pi )\lambda$, where $\alpha$ is the fine-structure constant. Thus, for long wavelengths, the region has macroscopic dimensions. The energy–time uncertainty relation predicts a maximum possible radius that is larger than the radius based on the radiative shift calculations by a factor of $1/4\alpha$. Full article

The critical properties of a discrete version of opinion dynamics systems, based on the Biswas–Chatterjee–Sen model defined on Solomon networks with both nearest and random neighbors, are investigated through extensive computer simulations. By employing Monte Carlo algorithms on SNs of different sizes, the magnetic-like variables of the model are computed as a function of the noise parameter. Using the finite-size scaling hypothesis, it is observed that the model undergoes a second-order phase transition. The critical transition noise and the respective ratios of the usual critical exponents are computed in the limit of infinite-size networks. The results strongly indicate that the discrete Biswas–Chatterjee–Sen model is in a different universality class from the other lattices and networks, but in the same universality class as the Ising and majority-vote models on the same Solomon networks. Full article

In this paper we extend the Zeldovich formula, which was originally derived for the free electromagnetic field and was interpreted as the number of photons. We show that our extended formula gives a universal dimensionless measure of the overall strength of electromagnetic fields: free fields and fields produced by various sources, in both the classical and the quantum theory. In particular, we find that this number—called here the Zeldovich number—for macroscopic systems is very large, of the order of ${10}^{20}$. For the hydrogen atom in the ground state, the Zeldovich number is equal to 0.025 and for the xenon atom it is around 50. Full article

Social physics (or sociophysics) offers new research perspectives for addressing social issues in various domains. In this study, we explore the decision-making process of doctoral graduates during their transition from graduation to employment, drawing on the ideas of sociophysics. We divide the process into two decision steps and propose a generative model based on appropriate assumptions. This model effectively reproduces empirical data, allowing us to derive essential parameters that influence the decision-making process from empirical observations. Through a comparison of the best-fit parameters, we discover that doctoral graduates in business disciplines tend to exhibit more concentrated employment choices, while those in computer science and history disciplines demonstrate a greater diversity of options. Furthermore, we observe that universities consider factors beyond rankings when selecting doctoral graduates. Full article

We analyze the (dynamical) classic limit of a special semiclassical system. We describe the interaction of a quantum system with a classical one. This limit has been well studied before as a function of a constant of motion linked to the Heisenberg principle. In this paper, we investigate the existence of the mentioned limit, but with reference to the total energy of the system. Additionally, we find an attractive result regarding the border of the transition. Full article

A new method for studying two-particle transverse momentum ($P_T$) correlations in soft hadronic interactions is proposed. It is shown that Monte Carlo models: PYTHIA 6 and Geant4 FTF (FRITIOF), give different predictions for the correlations in proton–proton interactions. The correlations are connected with Schwinger’s mechanism of particle creation. These correlations can be studied in current and future experiments in high energy physics, in particular, at the Nuclotron-based Ion Collider fAcility (NICA). Full article

The Casimir forces between metals or good conductors have been checked experimentally. Semiconductors and especially dielectrics have not been investigated because of the surface charges, which generate strong electrostatic forces. Here, it is proposed to study the Casimir interaction of a dielectric and metal using a thin dielectric layer deposited on an optically thick metallic substrate. If the thickness of the layer is a few tens of nanometers, the electrostatic force due to charging can be compensated for by applying an extra voltage between the metallic plates. On the other hand, the contribution of the dielectric layer to the Casimir force is sufficiently large to extract information about the interaction between the bulk dielectric and metal. Full article

Classical radiation from a single relativistically accelerating electron is investigated where the temperature characterizing the system highlights the dependence on acceleration. In the context of the dynamic Casimir effect with Planck-distributed photons and thermal black hole evaporation, we demonstrate analytic consistency between the ideas of constant acceleration and equilibrium thermal radiation. For ultra-relativistic speeds, we demonstrate a long-lasting constant peel acceleration and constant power emission, which is consistent with the idea of balanced equilibrium of Planck-distributed particle radiation. Full article

In the classical approach to dealing with near-field radiative heat exchange between two closely spaced bodies, no coupling between the different heat carriers inside the materials and thermal photons is usually considered. Here, we provide an overview of the current state of research on this coupling between solids of different sizes while paying specific attention to the impact of the conduction regime inside the solids on the conduction–radiation coupling. We describe how the shape of the solids affects this coupling, and show that it can be located at the origin of a drastic change in the temperature profiles inside each body and the heat flux exchanged between them. These results could have important implications in the fields of nanoscale thermal management, near-field solid-state cooling, and nanoscale energy conversion. Full article

The experimental data from VENUS, TOPAS, OPAL, DELPHI, ALEPH and L3 Collaborations collected from 1989 to 2003 are applied to study the quantum electrodynamics (QED) framework through the direct contact interaction term approach, using the annihilation reaction $e^{+}{e}^{-}\to \gamma \gamma \left(\gamma \right)$. The analysis involves performing a ${\chi }^2$-test to detect the presence of an excited electron $e^{*}$, and and evidence of non-point like behavior in the $e^{+}{e}^{-}$ annihilation zone. The analysis yields compelling results, showing a significant signal at a confidence level of approximately 5 standard deviations. These findings suggest the existence of an excited electron with a mass of 308 ± 14 GeV and indicate the presence of a contact interaction characterized by a cutoff scale of 1253.53 ± 226 GeV. Furthermore, the interpretation of the cutoff scale result in terms of a radius of (1.57 ± 0.07) × 10⁻¹⁷ cm raises an intriguing possibility regarding the electron’s non-pointness. Full article

This paper is devoted to nonequilibrium systems in the physics approach to social systems. Equilibrium systems have been considered in the recenly published first part of the review. The style of the paper combines the features of a tutorial and a review, which, from one side, makes it simpler to read for nonspecialists aiming at grasping the basics of social physics, and from the other side, describes several rather recent original models containing new ideas that could be of interest to experienced researchers in the field. Full article

This paper is devoted to the current status of the novel fully active 3D (three-dimensional) fine-grained scintillator detector SuperFGD as a main part of the near off-axis detector upgrade program for the T2K experiment. The following important components related to the SuperFGD such as SuperFGD electronics and mechanics, wavelength shifting (WLS) fibers, and light emitting diode (LED) calibration system are also discussed here as well as the detector’s near future. Full article

In this paper, we review the physics studies to be performed with the Spin Physics Detector (SPD) at the Nuclotron-based Ion Collider fAcility (NICA) which is a multi-purpose experiment designed to study nucleon spin structure in the three dimensions. With capabilities to collide polarized protons and deuterons with center-of-mass energy up to 27 GeV and luminosity up to ${10}^{32}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ for protons (an order of magnitude less for deuterons), the experiment is considered to allow measurements of cross-sections and spin asymmetries of hadronic processes sensitive to the unpolarized and various polarized (helicity, Sivers, Boer-Mulders) gluon distributions inside the nucleons. Results from the SPD will be complimentary to the present high-energy spin experiments at the RHIC (Relativistic Heavy Ion Collider) facility or future experiments such as the Electron-Ion Collider (EIC) at BNL (Brookhaven National Laboratory) and the AFTER experiment at the LHC (Large Hadron Collider) in understanding the spin structure of the basic building blocks of visible matter. Monte Carlo simulation-based results presented here demonstrate the impact of the SPD asymmetry measurements on gluon helicity parton distribution function (PDF) and gluon Sivers functions. With polarized deuteron collisions, the SPD is expected to be the unique laboratory for probing tensor-polarized gluon distributions. Additionally, there are possibilities of colliding other light nuclei, such as carbon, at reduced collision energy and luminosity during the first stage of the experiment. Full article