494 research outputs found
Reconsidering the quantization of electrodynamics with boundary conditions and some measurable consequences
We show that the commonly known conductor boundary conditions
can be realized in two ways which we call 'thick' and 'thin'
conductor. The 'thick' conductor is the commonly known approach and includes a
Neumann condition on the normal component of the electric field
whereas for a 'thin' conductor remains without boundary condition.
Both types describe different physics already on the classical level where a
'thin' conductor allows for an interaction between the normal components of
currents on both sides. On quantum level different forces between a conductor
and a single electron or a neutral atom result. For instance, the
Casimir-Polder force for a 'thin' conductor is by about 13% smaller than for a
'thick' one.Comment: 22 pages, basic statement weakened, conclusions changed, misprints
correcte
Casimir force under the influence of real conditions
The Casimir force is calculated analytically for configurations of two
parallel plates and a spherical lens (sphere) above a plate with account of
nonzero temperature, finite conductivity of the boundary metal and surface
roughness. The permittivity of the metal is described by the plasma model. It
is proved that in case of the plasma model the scattering formalism of quantum
field theory in Matsubara formulation underlying Lifshitz formula is well
defined and no modifications are needed concerning the zero-frequency
contribution. The temperature correction to the Casimir force is found
completely with respect to temperature and perturbatively (up to the second
order in the relative penetration depth of electromagnetic zero-point
oscillations into the metal) with respect to finite conductivity. The
asymptotics of low and high temperatures are presented and contributions of
longitudinal and perpendicular modes are determined separately. Serving as an
example, aluminium test bodies are considered showing good agreement between
the obtained analytical results and previously performed numerical
computations. The roughness correction is formally included and formulas are
given permitting to calculate the Casimir force under the influence of all
relevant factors
Heat Kernel Expansion for Semitransparent Boundaries
We study the heat kernel for an operator of Laplace type with a
-function potential concentrated on a closed surface. We derive the
general form of the small asymptotics and calculate explicitly several
first heat kernel coefficients.Comment: 16 page
The ground state energy of a spinor field in the background of a finite radius flux tube
We develop a formalism for the calculation of the ground state energy of a
spinor field in the background of a cylindrically symmetric magnetic field. The
energy is expressed in terms of the Jost function of the associated scattering
problem. Uniform asymptotic expansions needed are obtained from the
Lippmann-Schwinger equation. The general results derived are applied to the
background of a finite radius flux tube with a homogeneous magnetic field
inside and the ground state energy is calculated numerically as a function of
the radius and the flux. It turns out to be negative, remaining smaller by a
factor of than the classical energy of the background except for very
small values of the radius which are outside the range of applicability of QED.Comment: 25 pages, 3 figure
Electromagnetic vacuum energy for two parallel slabs in terms of surface, wave guide and photonic modes
The formulation of the Lifshitz formula in terms of real frequencies is
reconsidered for half spaces described by the plasma model. It is shown that
besides the surface modes (for the TM polarization), and the photonic modes,
also waveguide modes must be considered.Comment: some references adde
Drude model and Lifshitz formula
Since nearly 10 years, it is known that inserting the permittivity of the
Drude model into the Lifshitz formula for free energy causes a violation of the
third law of thermodynamics. In this paper we show that the standard Matsubara
formulation for free energy contains a contribution that is non-perturbative in
the relaxation parameter. We argue that the correct formula must have a
perturbative expansion and conclude that the standard Matsubara formulation
with the permittivity of the Drude model inserted is not correct. We trace the
non-perturbative contribution in the complex frequency plane, where it shows up
as a self-intersection or a bifurcation of the integration path.Comment: accepted for publication in EPJ
Critical surface band gap of repulsive Casimir interaction between three dimensional topological insulators at finite temperature
We generalize the calculation of Casimir interaction between topological
insulators with opposite topological magnetoelectric polarizabilities and
finite surface band gaps to finite Temperature cases. We find that finite
temperature quantitatively depress the repulsive peak and enlarge the critical
surface gap for repulsive Casimir force. However the universal property
is still valid for various oscillation strength, temperature
region and topological magnetoelectric polarizabilities.Comment: 7 pages, 4 figure
Dynamical Casimir Effect in a one-dimensional uniformly contracting cavity
We consider particle creation (the Dynamical Casimir effect) in a uniformly
contracting ideal one-dimensional cavity non-perturbatively. The exact
expression for the energy spectrum of created particles is obtained and its
dependence on parameters of the problem is discussed. Unexpectedly, the number
of created particles depends on the duration of the cavity contracting
non-monotonously. This is explained by quantum interference of the events of
particle creation which are taking place only at the moments of acceleration
and deceleration of a boundary, while stable particle states exist (and thus no
particles are created) at the time of contracting.Comment: 13 pages, 4 figure
Ground State Energy of Massive Scalar Field in the Background of Finite Thickness Cosmic String
We calculate the ground state energy of a massive scalar field in the
background of a cosmic string of finite thickness (Gott-Hiscock metric). Using
zeta functional regularization we discuss the renormalization and the relevant
heat kernel coefficients in detail. The finite (non local) part of the ground
state energy is calculated in 2+1 dimensions in the approximation of a small
mass density of the string. By a numerical calculation it is shown to vanish as
a function of the radius of the string and of the parameter of the
nonconformal coupling.Comment: 23 pages, Latex, 3 figures, subm. to Phys. Rev.
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