The principle of binding energy conservation during charge conjugation and the hypothesis of gravitational repulsion of antiparticle masses is used to formulate appropriate two-component hydrodynamics. The dispersion relation for small perturbations is obtained and analyzed. The modified Jeans instability for matter-antimatter system is found as the function of arbitrary fraction of the repulsive matter. For the hydrogen-antihydrogen system, the recent ALPHA-g experimental result is used to apply to the early Universe evolution. It is shown that the non-damping sound mode exists if the annihilation damping is absent.

The optical properties of a nonideal fully ionized plasma are discussed using kinetic theory. It is shown that plasma conductivity in a moderately nonideal case in general requires accounting for the arbitrary degeneracy of the electron component of the plasma. The analytical results obtained generalize the recently developed consideration of the optical properties of plasma for nondegenerate electrons. Calculations were carried out for the static conductivity of plasma.

In a recent paper [Phys. Rev. E 100, 023202 (2019)], Munirov and Fish proposed application of the well-known approach for the calculation of the fluctuation field radiation spectrum in a transparent fully ionized plasma to the problem of cosmic microwave background. They used the result for spectral energy distribution of the equilibrium radiation, assuming that the spectrum of free photons is changed to the non-damping spectrum of transverse waves in non-relativistic plasma. The similar approach has been considered earlier by several authors for non-relativistic and relativistic plasmas. The results of Munirov and Fish are in fact in perfect agreement with the most of the previously existing expressions. However, we argue that this approach based on such simple approximation is not enough justified and the more elaborated consideration, taking into account not only temporal but also spatial dispersion of dielectric permittivity is necessary for a consistent description of radiation in plasmas. Moreover, interaction between free photons and charged particles in the framework of quantum electrodynamics leads to the result different in comparison with the standard consideration even for the transparent plasma medium.

Based on the discrete model of infection spread in a closed population, appearance of epidemic waves associated with strengthening and weakening quarantine measures in the present paper is shown. The effect of quarantine measures is considered in the model under consideration via time dependence in the infection transmission rate. It was shown that the epidemic development is controlled by four key parameters: the number of infected persons, the average virus carriage time (as applied to COVID-19-type epidemics caused by the virus SARS-CoV-2 spread), the average number of dangerous contacts (which can cause virus transfer from an infected person to healthy men) of one infectious person (virus carrier) per day and the probability of infection due to a hazardous contact. The two latter parameters enter the model only as a product called the indicator of infection growth (IG) in population. The found solutions depend also on the population size and on the initial number of infected persons. The IG in the model under consideration is similar in meaning to the reproductive number in continuous SIR and SEIR models. At the same time, due to the prolonged virus carriage characteristic of COVID-19, the solutions proposed here are based on the equations with delay, and even without temporal variations of the IG, differ significantly from the SIR and SEIR models. The effect of the feedback between the epidemic spread rate and variations in the IG, caused by strengthening or weakening quarantine measures is studied. It results in a principal change in the epidemic behavior, which not reaching the saturation mode, transforms to its wavy flow mode. The dependence of the onset of epidemic waves on characteristic times of quarantine restriction weakening was revealed. In the model under consideration, the possibility of complete epidemic end in the case of long-term restricted quarantine measures was shown. The possible existence of the quasi-steady mode of low-intensity epidemic was detected. In this mode, the number of virus carriers remains unchanged for a long time due to the balance of the number of infections and recoveries per day.

The consideration of dark energy is intended to explain the unexpected but observed acceleration of the universe. Baryon asymmetry in matter-antimatter initial annihilation is mostly accepted to explain the absence of observations of annihilation radiation that in turn leads to the most accepted hypothesis that we live in a matter dominated universe. These are two of the greatest puzzles in modern cosmology as they are not compatible with well-known and accepted physics. Here, we assume that antimatter gravitationally repels matter, knowing that it is not easily accepted in modern physics, but does not contradict the available experimental data especially since the inertial mass remains positive. On a cosmological-scale the universe in this hypothesis, even though it is gravitationally neutral with equal quantities of positive matter and negative antimatter domains, reveals the mechanism of expansion naturally due to repulsion between those domains. On local scales, we justify the absence of observations of annihilation radiation in possible matter-antimatter galaxy collisions on the gravitational repulsion and also the bouncing off due to annihilation explosion region between them. From the simulations that we performed, it is shown that the extracted data clearly create the Hubble expansion law regardless of the initial distribution of galaxies, their positions, velocities, masses, mergers/annihilations and other initial conditions, without the need for a dark energy component. It is also shown that, in specific initial density cases, the known bump that show acceleration in the Hubble diagram appears clearly, and in turn reveals the observed acceleration of the universe expansion, again without any dark energy involved.

The general structure of the perturbation theory series for the thermodynamic potential of a system of electrons and point ions is discussed. In the classical limit, when Planck’s constant ℏ → 0, the particular terms of the perturbation theory series diverge due to the impossibility of maintaining of stability of a purely classical system of the opposite sign charges attracted to each other. At the same time, it is known that in a certain range of parameters, a thermodynamic potential that does not contain Planck’s constant is a good approximation. Such thermodynamic functions describes the experimental data well and corresponds to the molecular dynamics calculations of model quasi-Coulomb systems. It is shown that the transition to a purely classical description, which implies the limit ℏ → 0, is impossible, but the terms of the series containing ℏ are small for certain plasma parameters and can be discarded. This is the rationale explanation of using classical models and approximations to describe plasma in certain parameter ranges. On this basis, a hypothesis is formulated about the absence of a classical limit for all measurable physical properties (including kinetic characteristics) of the Coulomb model of plasma, in which point particles interact according to the Coulomb law and, therefore, there are no adjustable parameters.

Based on a discrete model of the spread of infection in a closed population, the corresponding form of differential equations with delay is found. It is shown that the development of the epidemic is determined by four key parameters: the number of infectious persons, the average number of dangerous contacts of one infectious person per day, the probability of infection as a result of such contact, and the average time interval during which the sick person is able to infect others. The decision also depends on the size of the population and on the initial number of infected persons. The four named parameters have a clear meaning and are related to the well-known concept of reproductive number in the continuous Susceptible–Infectious–Recovered (SIR) and Susceptible–Infected–Infectious–Recovered (SEIR) models. The epidemic saturation conditions are established by solving the obtained differential equations. It is shown that, due to the long virus carrying characteristic of COVID-19, the solutions proposed here differ significantly from the SIR model.

The high-frequency asymptotic behavior of the spectral density of the distribution of equilibrium radiation in a nondegenerate electron gas is considered. It is shown that, at high frequencies, the expression for equilibrium radiation in a collisionless electron gas undergoes a renormalization of zero-point oscillations.

Based on the general expression for the spectral density of equilibrium radiation in a nonrelativistic plasma medium, the high-frequency asymptotics is found for an electron gas accounting for the spatial dispersion of the transverse dielectric permittivity. The necessity of modifying zero oscillations in the presence of a collisionless plasma medium is shown.

The recently developed model of the epidemic spread of two virus strains in a closed population is generalized to the situation typical for the couple of strains delta and omicron, when there is a high probability of omicron infection soon enough after recovering from delta infection. This model can be considered as a kind of combination of SIR and SIS models for the case of competition of two strains of the same virus with different contagiousness in a population. The obtained equations and results can be directly implemented for practical calculations of the replacement of strains of the SARS-CoV-2 virus. A comparison between the estimated replacement time and the corresponding statistics shows reasonable agreement.

Based on the formulas for the frequency-dependent conductivity of a moderately nonideal plasma, an expression is obtained for the spectral density of equilibrium radiation, which depends not only on the temperature, but also on the density of charged particles.

The SIR model of the epidemic spread is used for consideration the problem of the competition of two viruses having different contagiousness. It is shown how the more contagious strain replaces over time the less contagious one. In particular the results can be applied to the current situation when the omicron strain appeared in population affected by the delta strain.PACS number(s)02.50.-r, 05.60.-k, 82.39.-k, 87.19.Xx

The optical properties of non-ideal completely ionized plasma are discussed from the perspective of the kinetic theory approach. It is demonstrated that a physically motivated modification of the Coulomb logarithm, originally proposed in the context of ion-particle scattering in dusty plasma, allows us to improve the theoretical description of the dynamical conductivity and hence of the optical properties of plasma in the moderately non-ideal regime. The obtained analytical results for the refractive index, reduced absorption and reflection coefficients can be straightforwardly implemented for practical calculations. The comparison between experimental and theoretical results for the reflectivity is performed and discussed in some detail. (C) 2022 Elsevier Ltd. All rights reserved.

Equations for infection spread in a closed population are found in discrete approximation, corresponding to the published statistical data, and in continuous time in the form of delay differential equations. We consider the epidemic as dependent upon four key parameters: the size of population involved, the mean number of dangerous contacts of one infected person per day, the probability to transmit infection due to such contact and the mean duration of disease. In the simplest case of free-running epidemic in an infinite population, the number of infected rises exponentially day by day. Here we show the model for epidemic process in a closed population, constrained by isolation, treatment and so on. The four parameters introduced here have the clear sense and are in association with the well-known concept of reproduction number in the continuous susceptible– infectious–removed, susceptible–exposed–infectious–removed (SIR, SEIR) models. We derive the initial rate of infection spread from the published statistical data for the initial stage of epidemic, when the quarantine measures were absent. On this basis, we can found the corresponding basic reproduction number mentioned above. Our approach allows evaluating the influence of quarantine measures on free pandemic process that leads to the time-dependent rate of infection and suppression of infection. We found a good correspondence of the theory and reliable statistical data. The initially formulated discrete model, describing epidemic course day by day is transferred to differential form. The conditions for saturation of epidemic are found by solving the delay differential equations. They differ essentially from ones in SIR model due to finite delay, typical for COVID-19 The proposed model opens up the possibility to predict the optimal level of social quarantine measures. The model is quite flexible and it can be extended to more complex cases.

Based on the self-consistent Hartree–Fock approximation, the nonstationary equation is obtained for the one-particle wave function describing the Bose–Einstein condensate in a rarefied gas of spin-zero bosons. A rarefied gas of bosons is exposed to the static external field, which ensures its finite ground state. The derived equation allows one to correctly determine the ground state energy in the stationary case.

The asymptotic behavior of the equilibrium radiation in Maxwellian plasma is investigated for the region of low frequencies. It is shown, that already for a weakly non-ideal plasma the equilibrium radiation can essentially deviate from the Planck law. The deviation from the Planck distribution is described by the transverse dielectric permittivity which takes into account both frequency and spatial dispersion. The influence of plasma non-ideality increases with increase of the non-ideality parameter in the in the dielectric permittivity. The spectral energy distribution of the equilibrium radiation essentially changes in the region of observable frequencies. At asymptotically low frequencies there is transfer from logarithmic to power behavior of the equilibrium radiation. The results indicate that in the primordial plasma of Early Universe the spectral energy distribution of radiation could be different then the Planck one.

The simplest approximation for the first stages of the infection spread is considered. The specific feature of the COVID-19 characterized by its long latent period is taken into account. Exponential increase of numbers of infected people is determined by the half period of the maximal latent time for the COVID-19. The averaging over latent period leads to additional increase of the infected numbers.PACS number(s)02.50.-r, 05.60.-k, 82.39.-k, 87.19.Xx

Using the linear response theory and the concept of off-diagonal long-range order, the Kramers–Kronig relations for the dielectric permittivity of a disordered Coulomb system in the presence of a single-component Bose–Einstein condensate for nuclei are obtained.

A study of equilibrium radiation in plasma media shows that the spectral energy distribution of such radiation is different from the distribution of Planck equilibrium radiation. Using the quantum electrodynamic approach, a general relation was found for the spectral energy density of equilibrium radiation in a system of charged particles for opaque and transparent media.

The consideration of equilibrium radiation in plasma-like media shows that the spectral energy distribution of such radiation differs from that of Planck equilibrium radiation. Based on the previously derived relation for the spectral energy density of equilibrium radiation in the system of charged particles, accounting for finite damping in a medium with spatial dispersion, the limiting case of infinitesimal damping dispersion is considered. It was shown that zero-point vacuum fluctuations being a component of the total spectral energy distribution in the medium should be renormalized when using certain models for the transverse plasma permittivity. In this case, renormalized zero-point vacuum fluctuations become dependent on plasma parameters. The possibility of the manifestation of this effect is discussed.