arXiv subjects

Yu. Voronina

Publications and source records attributed to Yu. Voronina.

4 recordsLinked to original sources

arXiv2022

Super-critical QED-effects via VP-energy

The properties of the QED-vacuum energy $\hbox{$\cal E $}_{VP}$ under Coulomb super-criticality condition $Z>Z_{cr,1}$ are explored in essentially non-perturbative approach. It is shown that in the supercritical region $\hbox{$\cal E $}_{VP}$ is the decreasing function of the Coulomb source parameters, resulting in decay into the negative range as $\sim - Z^4/R$. The conditions, under which the emission of vacuum positrons can be unambiguously detected on the nuclear conversion pairs background, are also discussed. In particular, for a super-critical dummy nucleus with charge $Z$ and $R(Z) \simeq 1.2 \ (2.5\, Z)^{1/3}$ fm the lowest $1s$-level dives into the lower continuum at $Z_{cr,1} \simeq 170$ (the model of uniformly charged ball) or $Z_{cr,1} \simeq 173$ (the spherical shell model), whereupon there appears the vacuum shell with the induced charge (-$2|e|$) and the QED-vacuum becomes charged, but in both cases the actual threshold for reliable spontaneous positrons detection is not less than $Z^\ast \simeq 210$.

physics.atom-ph↗

arXiv2019

Casimir force variability in one-dimensional QED systems

The Casimir force between two short-range charge sources, embedded in a background of one dimensional massive Dirac fermions, is explored by means of the original $\ln\text{[Wronskian]}$ contour integration techniques. For identical sources with the same (positive) charge, we find that in the non-perturbative region the Casimir interaction between them can reach sufficiently large negative values and simultaneously reveal the features of a long-range force in spite of nonzero fermion mass, that could significantly influence the properties of such quasi-one-dimensional QED systems. For large distances $s$ between sources we recover that their mutual interaction is governed first of all by the structure of the discrete spectrum of a single source, in dependence on which it can be tuned to give an attractive, a repulsive, or an (almost) compensated Casimir force with various rates of the exponential fall-down, quite different from the standard $\exp (-2 m s)$ law. By means of the same $\ln\text{[Wronskian]}$ techniques, the case of two $δ$-sources is also considered in a self-consistent manner with similar results for the variability of the Casimir force. A quite different behavior of the Casimir force is found for the antisymmetric source-anti-source system. In particular, in this case, there is no possibility for a long-range interaction between sources. The asymptotics of the Casimir force follows the standard $\exp (-2 m s)$ law. Moreover, for small separations between sources, the Casimir force for symmetric and antisymmetric cases turns out to be of opposite sign.

hep-th↗

arXiv2018

Casimir (vacuum) energy in planar QED with strong coupling

The essentially non-perturbative vacuum polarization effects, caused by an extended external supercritical Coulomb source, are explored for a planar Dirac-Coulomb (DC) system with strong coupling (similar to graphene and graphene-based heterostructures). Taking account of results, obtained in \cite{partI2018} for the induced charge density $ρ_{VP}(\vec{r})$, in the present paper the evaluation of the Casimir (vacuum) energy $\mathcal{E}_{VP}$ is presented. The main result is that for a wide range of the system parameters in the overcritical region $\mathcal{E}_{VP}$ turns out to be a rapidly decreasing negative function $\sim - Z^3/R_0\, $ with $Z\, , R_0$ being the charge and the size of the external source. By an explicit calculation the possibility for complete screening of the electrostatic reflection self-energy of the external source by such polarization effects for $Z \gg Z_{cr,1}$ is demonstrated. The dependence of the Casimir energy on the screening of the Coulomb asymptotics of the external source at some $R_1>R_0$ is also explored in detail, and some peculiar effects in the partial channels with the lowest rotational numbers $m_j=\pm 1/2\, , \pm3/2$ in the screened case are also discussed.

cond-mat.mes-hall↗

arXiv2018

Essentially non-perturbative and peculiar polarization effects in planar QED with strong coupling

The essentially non-perturbative polarization effects are considered for a planar supercritical Dirac-Coulomb system with strong coupling (similar to graphene and graphene-based heterostructures) in terms of induced charge density $ρ_{VP}(\vec{r})$. The main attention is paid to the renormalization, convergence of the partial expansion and the behavior of $ρ_{VP}(\vec{r})$ and the integral induced charge $Q_{VP}$ in the overcritical region. The dependence of the induced density on the screening of the Coulomb asymptotics of the external source is also explored in detail. Some peculiar effects in the discrete spectrum with the lowest rotational numbers $m_j=\pm 1/2\, , \pm3/2$ in the screened case are detected and their possible role in the transition through corresponding $Z_{cr}$ is also discussed.

cond-mat.mes-hall↗