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Michael Bordag

Publications and source records attributed to Michael Bordag.

7 recordsLinked to original sources
arXiv2019

Vacuum energy for generalised Dirac combs at $T = 0$

The quantum vacuum energy for a hybrid comb of Dirac $δ$-$δ'$ potentials is computed using the energy of the single $δ$-$δ'$ potential over the real line that makes up the comb. The zeta function of a comb periodic potential is the continuous sum of zeta functions over the dual primitive cell of Bloch quasi-momenta. The result obtained for the quantum vacuum energy is non-perturbative in the sense that the energy function is not analytical for small couplings

math-ph↗
arXiv2018

Dispersion Forces Between Fields Confined to Half Spaces

We consider the Casimir effect for a scalar field interacting with another scalar field that is confined to two half spaces. This model is aimed to mimic the interaction of the photon field with matter in two slabs. We use Dirichlet boundary conditions on the interfaces for the fields in the half spaces and calculate their one-loop contribution to the wave equation for the other field. We perform the ultraviolet renormalization and develop a convenient formalism for the calculation of the vacuum energy in this configuration.

quant-ph↗
arXiv2013

On the Casimir repulsion in sphere-plate geometry

The electromagnetic vacuum energy is considered in the presence of a perfectly conducting plane and a ball with dielectric permittivity $\varepsilon$ and magnetic permeability $μ$, $μ\ne1$. The attention is focused on the Casimir repulsion in this system caused by magnetic permeability of the sphere. In the case of perfectly permeable sphere, $μ=\infty$, the vacuum energy is estimated numerically. The short and long distance asymptotes corresponding to the repulsive force and respective low temperature corrections and high temperature limits are found for a wide range of $μ$. The constraints on the Casimir repulsion in this system are discussed.

quant-ph↗
arXiv2011

Long range chromomagnetic fields at high temperature

The magnetic mass of neutral gluons in Abelian chromomagnetic field at high temperature is calculated in SU(2)$ gluodynamics. It is noted that such type fields are spontaneously generated at high temperature. The mass is computed either from the Schwinger-Dyson equation accounting for the one-loop polarization tensor or in Monte-Carlo simulations on a lattice. In latter case, an average magnetic flux penetrating a plaquette is measured for a number of lattices. Both calculations are in agreement with each other and result in zero magnetic mass. Some applications of the results obtained are discussed.

hep-ph↗
arXiv2010

The low temperature corrections to the Casimir force between a sphere and a plane

We calculate the low temperature corrections to the free energy for a sphere in front of a plane. First, the scalar field obeying Dirichet or Neumann boundary conditions is considered. Second, the electromagnetic field is studied, the sphere being perfectly conducting and being a dielectric ball with both, constant permittivity and permittivity of the plasma model.

quant-ph↗
arXiv1999

Once More on a Colour Ferromagnetic Vacuum State at Finite Temperature

The spontaneous vacuum magnetization at finite temperature is investigated in SU(2) gluodynamics within a consistent effective potential approach including the one-loop and the correlation correction contributions. To evaluate the latter ones the high temperature limits of the polarization operators of charged and neutral gluon fields in a covariantly constant magnetic field and at high temperature are calculated.The radiation mass squared of charged gluons is found to be positive. It is shown that the ferromagnetic vacuum state having a field strength of order $(gH)^{1/2} \sim g^{4/3} T$ is spontaneously generated at high temperature. The vacuum stability and some applications of the results obtained are discussed.

hep-ph↗