81 research outputs found
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
LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths
We present a new code for solving the molecular and atomic excitation and
radiation transfer problem in a molecular gas and predicting emergent spectra.
This code works in arbitrary three dimensional geometry using unstructured
Delaunay latices for the transport of photons. Various physical models can be
used as input, ranging from analytical descriptions over tabulated models to
SPH simulations. To generate the Delaunay grid we sample the input model
randomly, but weigh the sample probability with the molecular density and other
parameters, and thereby we obtain an average grid point separation that scales
with the local opacity. Our code does photon very efficiently so that the slow
convergence of opaque models becomes traceable. When convergence between the
level populations, the radiation field, and the point separation has been
obtained, the grid is ray-traced to produced images that can readily be
compared to observations. Because of the high dynamic range in scales that can
be resolved using this type of grid, our code is particularly well suited for
modeling of ALMA data. Our code can furthermore deal with overlapping lines of
multiple molecular and atomic species.Comment: 13 pages, 12 figures, Accepted by A&A on 06/08/201
Ultraviolet divergences, repulsive forces and a spherical plasma shell
We discuss the vacuum energy of the electromagnetic ¯eld interacting with a
spherical plasma shell together with a model for the classical motion of the shell. We discuss
the ultraviolet divergences in terms of the heat kernel coe±cients. Using these, we carry out
the renormalization by rede¯ning the parameters of the classical model. It turns out that this is
possible and that the resulting model has a vacuum energy which changes sign in dependence on
the parameters of the plasma shell. In the limit of the plasma shell becoming an ideal conductor
the vacuum energy found by Boyer in 1968 is reproduced
Vacuum Energy for a Scalar Field with Self-Interaction in (1 + 1) Dimensions
We calculate the vacuum (Casimir) energy for a scalar field with ϕ4 self-interaction in (1 + 1) dimensions non perturbatively, i.e., in all orders of the self-interaction. We consider massive and massless fields in a finite box with Dirichlet boundary conditions and on the whole axis as well. For strong coupling, the vacuum energy is negative indicating some instability
Revisiting the Casimir Energy with General Boundary Conditions, and applications in 1D Crystals
Producción CientíficaWe obtain new expressions for the Casimir energy between plates that are mimicked
by the most general possible boundary conditions allowed by the principles of quantum field theory. This result enables to provide the quantum vacuum energy for scalar fields propagating under the influence of a one-dimensional crystal represented by a periodic potential formed by an infinite array of identical potentials with compact support.MINECO (MTM2014-57129-C2-1-P) and Junta de Castilla y Leon (BU229P18 and VA137G18)
Fermionic Vacuum Energy from a Nielsen-Olesen Vortex
We calculate the vacuum energy of a spinor field in the background of a
Nielsen-Olesen vortex. We use the method of representing the vacuum energy in
terms of the Jost function on the imaginary momentum axis. Renormalization is
carried out using the heat kernel expansion and zeta functional regularization.
With this method well convergent sums and integrals emerge which allow for an
efficient numerical calculation of the vacuum energy in the given case where
the background is not known analytically but only numerically. The vacuum
energy is calculated for several choices of the parameters and it turns out to
give small corrections to the classical energy.Comment: 22 pages, 6 figure
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.Comment: 9 pages, 2 figure
CASIMIR ENERGIES IN SPHERICALLY SYMMETRIC BACKGROUND POTENTIALS REVISITED
In this paper we reconsider the formulation for the computation of the Casimir energy in spherically symmetric background potentials. Compared to the previous analysis, the technicalities are much easier to handle and final answers are surprisingly simple
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