arXiv subjects

P. Grashin

Publications and source records attributed to P. Grashin.

3 recordsLinked to original sources

arXiv2023

Spontaneous emission in the supercritical QED: what is wrong and what is possible

Spontaneous positron emission, caused by the supercritical Coulomb source with charge $Z$ and size $R$, is explored in essentially non-perturbative approach with emphasis on the VP-energy $\cal E_{VP}$, considered as a function of the Coulomb source parameters $Z$ and $R$. The specific contribution to $\cal E_{VP}$, which appears in the supercritical case due to direct Coulomb interaction between VP-charge densities $\varrho_{VP}(\vec{r})$, is outlined and studied in detail. It is shown that after first levels diving into the lower continuum this contribution, being properly renormalized, turns out to be negative in contrast to the classical electrostatics and so could play an important role in spontaneous emission, especially for $Z$ just above the first $Z_{cr,1}$. The additional problems of spontaneous emission, caused by the lepton number conservation, are also discussed.

hep-ph↗

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↗