Heat kernel Coefficients and Divergencies of the Casimir Energy for the Dispersive Sphere

The first heat kernel coefficients are calculated for a dispersive ball whose permittivity at high frequency differs from unity by inverse powers of the frequency. The corresponding divergent part of the vacuum energy of the electromagnetic field is given and ultraviolet divergencies are seen to be present. Also in a model where the number of atoms is fixed the pressure exhibits infinities. As a consequence, the ground-state energy for a dispersive dielectric ball cannot be interpreted easily.Comment: 8 pages, Contribution to the 5th Workshop on Quantum Field Theory under the Influence of External Conditions, Leipzig, Germany, 10-14 Sep 200

On the Vacuum energy of a Color Magnetic Vortex

We calculate the one loop gluon vacuum energy in the background of a color magnetic vortex for SU(2) and SU(3). We use zeta functional regularization to obtain analytic expressions suitable for numerical treatment. The momentum integration is turned to the imaginary axis and fast converging sums/integrals are obtained. We investigate numerically a number of profiles of the background. In each case the vacuum energy turns out to be positive increasing in this way the complete energy and making the vortex configuration less stable. In this problem bound states (tachyonic modes) are present for all investigated profiles making them intrinsically unstable.Comment: 28 pages, 4 figure

Generalized Lifshitz formula for a cylindrical plasma sheet in front of a plane beyond proximity force approximation

We calculate the first correction beyond proximity force approximation for a cylindrical graphene sheet in interaction with a flat graphene sheet or a dielectric half space.Comment: 35 pages, 8 figure

Vacuum energy between a sphere and a plane at finite temperature

We consider the Casimir effect for a sphere in front of a plane at finite temperature for scalar and electromagnetic fields and calculate the limiting cases. For small separation we compare the exact results with the corresponding ones obtained in proximity force approximation. For the scalar field with Dirichlet boundary conditions, the low temperature correction is of order $T^2$ like for parallel planes. For the electromagnetic field it is of order $T^4$. For high temperature we observe the usual picture that the leading order is given by the zeroth Matsubara frequency. The non-zero frequencies are exponentially suppressed except for the case of close separation.Comment: 14 pages, 3 figures, revised version with several improvement

Low temperature expansion in the Lifshitz formula

The low temperature expansion of the free energy in a Casimir effect setup is considered in detail. The starting point is the Lifshitz formula in Matsubara representation and the basic method is its reformulation using the Abel-Plana formula making full use of the analytic properties. This provides a unified description of specific models. We re-derive the known results and, in a number of cases, we are able to go beyond. We also discuss the cases with dissipation. It is an aim of the paper to give a coherent exposition of the topic. The paper includes the derivations and should provide a self contained representation.Comment: Final version, to appear in 'Advances in Mathematical Physics

First analytic correction beyond PFA for the electromagnetic field in sphere-plane geometry

We consider the vacuum energy for a configuration of a sphere in front of a plane, both obeying conductor boundary condition, at small separation. For the separation becoming small we derive the first next-to-leading order of the asymptotic expansion in the separation-to-radius ratio \ep. This correction is of order \ep. In opposite to the scalar cases it contains also contributions proportional to logarithms in first and second order, \ep \ln \ep and \ep (\ln \ep)^2. We compare this result with the available findings of numerical and experimental approaches.Comment: 20 pages, 1 figur

Casimir force between Chern-Simons surfaces

We calculate the Casimir force between two parallel plates if the boundary conditions for the photons are modified due to presence of the Chern-Simons term. We show that this effect should be measurable within the present experimental technique.Comment: 8 pages, 1 figur