31 research outputs found
Trajectories in a space with a spherically symmetric dislocation
We consider a new type of defect in the scope of linear elasticity theory,
using geometrical methods. This defect is produced by a spherically symmetric
dislocation, or ball dislocation. We derive the induced metric as well as the
affine connections and curvature tensors. Since the induced metric is
discontinuous, one can expect ambiguity coming from these quantities, due to
products between delta functions or its derivatives, plaguing a description of
ball dislocations based on the Geometric Theory of Defects. However, exactly as
in the previous case of cylindric defect, one can obtain some well-defined
physical predictions of the induced geometry. In particular, we explore some
properties of test particle trajectories around the defect and show that these
trajectories are curved but can not be circular orbits.Comment: 11 pages, 3 figure
Renormalization Ambiguities and Conformal Anomaly in Metric-Scalar Backgrounds
We analyze the problem of the existing ambiguities in the conformal anomaly
in theories with external scalar field in curved backgrounds. In particular, we
consider the anomaly of self-interacting massive scalar field theory and of
Yukawa model in the massless conformal limit. In all cases the ambiguities are
related to finite renormalizations of a local non-minimal terms in the
effective action. We point out the generic nature of this phenomenon and
provide a general method to identify the theories where such an ambiguity can
arise.Comment: RevTeX, 10 pages, no figures. Small comment and two references added.
Accepted for publication in Physical Review
On the static solutions in gravity with massive scalar field in three dimensions
We investigate circularly symmetric static solutions in three-dimensional
gravity with a minimally coupled massive scalar field. We integrate numerically
the field equations assuming asymptotic flatness, where black holes do not
exist and a naked singularity is present. We also give a brief review on the
massless cases with cosmological constant.Comment: 11 pages, LaTeX, 1 Postscript figure. Some changes were don
Universality and ambiguity in fermionic effective actions
We discuss an ambiguity in the one-loop effective action of massive fields
which takes place in massive fermionic theories. The universality of
logarithmic UV divergences in different space-time dimensions leads to the
non-universality of the finite part of effective action, which can be called
the non-local multiplicative anomaly. The general criteria of existence of this
phenomena are formulated and applied to fermionic operators with different
external fields.Comment: 13 pages, no figure
On Possible Light-Torsion Mixing in Background Magnetic Field
The interaction of the light with propagating axial torsion fields in the
presence of an external magnetic field has been investigated. Axial torsion
fields appearing in higher derivative quantum gravity possess two states, with
spin one and zero, with different masses. The torsion field with spin-0 state
is a ghost that can be removed if its mass is infinite. We investigate the
possibility when the light mixes with the torsion fields resulting in the
effect of vacuum birefringence and dichroism. The expressions for ellipticity
and the rotation of light polarization axis depending on the coupling constant
and the external magnetic field have been obtained.Comment: 12 pages, title changed, shortened journal version, accepted in
Eur.Phys.J.
Slowly rotating charged black holes in anti-de Sitter third order Lovelock gravity
In this paper, we study slowly rotating black hole solutions in Lovelock
gravity (n=3). These exact slowly rotating black hole solutions are obtained in
uncharged and charged cases, respectively. Up to the linear order of the
rotating parameter a, the mass, Hawking temperature and entropy of the
uncharged black holes get no corrections from rotation. In charged case, we
compute magnetic dipole moment and gyromagnetic ratio of the black holes. It is
shown that the gyromagnetic ratio keeps invariant after introducing the
Gauss-Bonnet and third order Lovelock interactions.Comment: 14 pages, no figur
The background scale Ward identity in quantum gravity
We show that with suitable choices of parametrization, gauge fixing and cutoff, the anomalous variation of the effective action under global rescalings of the background metric is identical to the derivative with respect to the cutoff, i.e. to the beta functional, as defined by the exact RG equation. The Ward identity and the RG equation can be combined, resulting in a modified flow equation that is manifestly invariant under global background rescalings
Tests of Lorentz symmetry using antihydrogen
Signals of CPT and Lorentz violation are possible in the context of
spectroscopy using hydrogen and antihydrogen. We apply the Standard-Model
Extension, a broad framework for Lorentz breaking in physics, to various
transitions in the hydrogen and antihydrogen spectra. The results show an
unsuppressed effect in the transition between the upper two hyperfine sublevels
of the ground state of these systems. We also discuss related tests in Penning
traps, and recent work on Lorentz violation in curved spacetime.Comment: 11pp, invited talk at PQE 37 Conference, Snowbird, Utah, USA, 2-6 Jan
200
Effective Action of Vacuum: Semiclassical Approach
We present brief, to great extent pedagogical review on renormalization in
curved space-time and of some recent results on the derivation and better
understanding of quantum corrections to the action of gravity. The paper is
mainly devoted to the semiclassical approach, but we also discuss its
importance for quantum gravity and string theory.Comment: 54 pages, 2 figures, invited review paper partially based on various
lecture courses, accepted in Classical and Quantum Gravity as topical review.
A few changes compared to the original version: some relevant comments on
black hole case and references added, typos correcte
Non-singular screw dislocations as the Coulomb gas with smoothed out coupling and the renormalization of the shear modulus
A field theory is developed for a thermodynamical description of array of
parallel non-singular screw dislocations in elastic cylinder. The partition
function of the system is considered in the functional integral form.
Self-energy of the dislocation cores is chosen in the form suggested by the
gauge-translational model of non-singular screw dislocation. It is shown that
the system of the dislocations is equivalent to the two-dimensional Coulomb
gas. The coupling potential is prevented from a short-distance divergency since
the core energies are taken into account. Two-point correlation functions of
the stress components are obtained. Renormalization of the shear modulus caused
by the presence of the dislocations is studied in the approximation of
non-interacting dislocation dipoles. It is demonstrated that the finite size of
the dislocation cores results in a modification of the renormalization law.Comment: 20 pages, LaTe