1,197 research outputs found
Effective Finite Temperature Partition Function for Fields on Non-Commutative Flat Manifolds
The first quantum correction to the finite temperature partition function for
a self-interacting massless scalar field on a dimensional flat manifold
with non-commutative extra dimensions is evaluated by means of dimensional
regularization, suplemented with zeta-function techniques. It is found that the
zeta function associated with the effective one-loop operator may be nonregular
at the origin. The important issue of the determination of the regularized
vacuum energy, namely the first quantum correction to the energy in such case
is discussed.Comment: amslatex, 14 pages, to appear in Phys. Rev.
On the issue of imposing boundary conditions on quantum fields
An interesting example of the deep interrelation between Physics and
Mathematics is obtained when trying to impose mathematical boundary conditions
on physical quantum fields. This procedure has recently been re-examined with
care. Comments on that and previous analysis are here provided, together with
considerations on the results of the purely mathematical zeta-function method,
in an attempt at clarifying the issue. Hadamard regularization is invoked in
order to fill the gap between the infinities appearing in the QFT renormalized
results and the finite values obtained in the literature with other procedures.Comment: 13 pages, no figure
The Casimir Effect for Generalized Piston Geometries
In this paper we study the Casimir energy and force for generalized pistons
constructed from warped product manifolds of the type where
is an interval of the real line and is a smooth compact
Riemannian manifold either with or without boundary. The piston geometry is
obtained by dividing the warped product manifold into two regions separated by
the cross section positioned at . By exploiting zeta function
regularization techniques we provide formulas for the Casimir energy and force
involving the arbitrary warping function and base manifold .Comment: 16 pages, LaTeX. To appear in the proceedings of the Conference on
Quantum Field Theory Under the Influence of External Conditions (QFEXT11).
Benasque, Spain, September 18-24, 201
One Loop Counterterms in 2D Dilaton-Maxwell Quantum Gravity
The renormalization structure of two-dimensional quantum gravity is
investigated, in a covariant gauge. One-loop divergences of the effective
action are calculated. All the surface divergent terms are taken into account,
thus completing previous one-loop calculations of the theory. It is shown that
the on-shell effective action contains only surface divergences. The off-shell
renormalizability of the theory is discussed and classes of renormalizable
dilaton and Maxwell potentials are found.Comment: 9 pages, LaTeX file, HUPD-92-1
Fluctuations of quantum fields via zeta function regularization
Explicit expressions for the expectation values and the variances of some
observables, which are bilinear quantities in the quantum fields on a
D-dimensional manifold, are derived making use of zeta function regularization.
It is found that the variance, related to the second functional variation of
the effective action, requires a further regularization and that the relative
regularized variance turns out to be 2/N, where N is the number of the fields,
thus being independent on the dimension D. Some illustrating examples are
worked through.Comment: 15 pages, latex, typographical mistakes correcte
Dynamical Casimir Effect with Semi-Transparent Mirrors, and Cosmology
After reviewing some essential features of the Casimir effect and,
specifically, of its regularization by zeta function and Hadamard methods, we
consider the dynamical Casimir effect (or Fulling-Davis theory), where related
regularization problems appear, with a view to an experimental verification of
this theory. We finish with a discussion of the possible contribution of vacuum
fluctuations to dark energy, in a Casimir like fashion, that might involve the
dynamical version.Comment: 11 pages, Talk given in the Workshop ``Quantum Field Theory under the
Influence of External Conditions (QFEXT07)'', Leipzig (Germany), September 17
- 21, 200
Casimir Effect for Spherical Shell in de Sitter Space
The Casimir stress on a spherical shell in de Sitter background for massless
scalar field satisfying Dirichlet boundary conditions on the shell is
calculated. The metric is written in conformally flat form. Although the metric
is time dependent no particles are created. The Casimir stress is calculated
for inside and outside of the shell with different backgrounds corresponding to
different cosmological constants. The detail dynamics of the bubble depends on
different parameter of the model. Specifically, bubbles with true vacuum inside
expand if the difference in the vacuum energies is small, otherwise they
collapse.Comment: 9 pages, submitted to Class. Quantum Gra
Black hole and de Sitter solutions in a covariant renormalizable field theory of gravity
It is shown that Schwarzschild black hole and de Sitter solutions exist as
exact solutions of a recently proposed relativistic covariant formulation of
(power-counting) renormalizable gravity with a fluid. The formulation without a
fluid is also presented here. The stability of the solutions is studied and
their corresponding entropies are computed, by using the covariant Wald method.
The area law is shown to hold both for the Schwarzschild and for the de Sitter
solutions found, confirming that, for the case, one is dealing with a
minimal modification of GR.Comment: 7 paages, latex fil
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