506 research outputs found
Casimir interaction of strained graphene
We calculate the Casimir interaction of two freestanding graphene samples
under uniaxial strain. Our approach fully takes retardation and dispersion into
account and is based on quantum field theoretical expressions for
conductivities in terms of the polarization operator. The force shows a rather
weak dependence on the realistic values of strain, changing just by a few
percent in its maximum as compared to the non-strained case.Comment: 5 pages, 3 figures, EPL style, misprint correcte
Vacuum energy in the presence of a magnetic string with delta function profile
We present a calculation of the ground state energy of massive spinor fields
and massive scalar fields in the background of an inhomogeneous magnetic string
with potential given by a delta function. The zeta functional regularization is
used and the lowest heat kernel coefficients are calculated. The rest of the
analytical calculation adopts the Jost function formalism. In the numerical
part of the work the renormalized vacuum energy as a function of the radius
of the string is calculated and plotted for various values of the strength of
the potential. The sign of the energy is found to change with the radius. For
both scalar and spinor fields the renormalized energy shows no logarithmic
behaviour in the limit , as was expected from the vanishing of the heat
kernel coefficient , which is not zero for other types of profiles.Comment: 30 pages, 10 figure
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
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
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
On the ground state energy for a penetrable sphere and for a dielectric ball
We analyse the ultraviolet divergencies in the ground state energy for a
penetrable sphere and a dielectric ball. We argue that for massless fields
subtraction of the ``empty space'' or the ``unbounded medium'' contribution is
not enough to make the ground state energy finite whenever the heat kernel
coefficient is not zero. It turns out that for a penetrable
sphere, a general dielectric background and the dielectric ball. To our
surprise, for more singular configurations, as in the presence of sharp
boundaries, the heat kernel coefficients behave to some extend better than in
the corresponding smooth cases, making, for instance, the dilute dielectric
ball a well defined problem.Comment: 18 pages, 1 figure, subm. to Phys. Rev.
Ground state energy in a wormhole space-time
The ground state energy of the massive scalar field with non-conformal
coupling on the short-throat flat-space wormhole background is calculated
by using zeta renormalization approach. We discuss the renormalization and
relevant heat kernel coefficients in detail. We show that the stable
configuration of wormholes can exist for . In particular case of
massive conformal scalar field with , the radius of throat of stable
wormhole . The self-consistent wormhole has radius of throat
and mass of scalar boson ( and
are the Planck length and mass, respectively).Comment: revtex, 18 pages, 3 eps figures. accepted in Phys.Rev.
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