63 research outputs found
Quantum Group Covariance and the Braided Structure of Deformed Oscillators
The connection between braided Hopf algebra structure and the quantum group
covariance of deformed oscillators is constructed explicitly. In this context
we provide deformations of the Hopf algebra of functions on SU(1,1). Quantum
subgroups and their representations are also discussed.Comment: 12 pages, to be published in JM
Braided Oscillators
The braided Hopf algebra structure of the generalized oscillator is
investigated. Using the solutions two types of braided Fibonacci oscillators
are introduced. This leads to two types of braided Biedenharn-Macfarlane
oscillators.Comment: 12 pages, latex, some references added, published versio
Bardeen spacetime as a quantum corrected Schwarzschild black hole: Quasinormal modes and Hawking radiation
The Bardeen black hole holds historical significance as the first model of a
regular black hole. Recently, there have been proposed interpretations of the
Bardeen spacetime as quantum corrections to the Schwarzschild solution. Our
study focuses on investigating the quasinormal modes and Hawking radiation of
the Bardeen black hole. We have observed that previous studies on the
quasinormal modes for the Bardeen black hole suffer from inaccuracies that
cannot be neglected. Therefore, we propose accurate calculations of the
quasinormal modes for scalar, electromagnetic, and neutrino fields in the
Bardeen spacetime. Additionally, we have computed the grey-body factors and
analyzed the emission rates of Hawking radiation. Even when the quantum
correction is small and the fundamental mode only slightly differs from its
Schwarzschild value, the first several overtones deviate at an increasingly
stronger rate. This deviation leads to the appearance of overtones with very
small real oscillation frequencies. This outburst of overtones is closely
linked to the fact that the quantum-corrected black hole differs from its
classical limit primarily near the event horizon. Moreover, the intensity of
the Hawking radiation is significantly suppressed (up to three orders of
magnitude) by the quantum correction.Comment: 12 pages, 9 figure
General Relativistic Thermoelectric Effects in Superconductors
We discuss the general-relativistic contributions to occur in the
electromagnetic properties of a superconductor with a heat flow. The appearance
of general-relativistic contribution to the magnetic flux through a
superconducting thermoelectric bimetallic circuit is shown. A response of the
Josephson junctions to a heat flow is investigated in the general-relativistic
framework. Some gravitothermoelectric effects which are observable in the
superconducting state in the Earth's gravitational field are considered.Comment: 13 pages, 2 figure
Ohm's Law for Plasma in General Relativity and Cowling's Theorem
The general-relativistic Ohm's law for a two-component plasma which includes
the gravitomagnetic force terms even in the case of quasi-neutrality has been
derived. The equations that describe the electromagnetic processes in a plasma
surrounding a neutron star are obtained by using the general relativistic form
of Maxwell equations in a geometry of slow rotating gravitational object. In
addition to the general-relativistic effect first discussed by Khanna \&
Camenzind (1996) we predict a mechanism of the generation of azimuthal current
under the general relativistic effect of dragging of inertial frames on radial
current in a plasma around neutron star. The azimuthal current being
proportional to the angular velocity of the dragging of inertial
frames can give valuable contribution on the evolution of the stellar magnetic
field if exceeds (
is the number density of the charged particles, is the conductivity of
plasma). Thus in general relativity a rotating neutron star, embedded in
plasma, can in principle generate axial-symmetric magnetic fields even in
axisymmetry. However, classical Cowling's antidynamo theorem, according to
which a stationary axial-symmetric magnetic field can not be sustained against
ohmic diffusion, has to be hold in the general-relativistic case for the
typical plasma being responsible for the rotating neutron star.Comment: Accepted for publication in Astrophysics & Space Scienc
Magnetic Fields of Spherical Compact Stars in Braneworld
We study the dipolar magnetic field configuration in dependence on brane
tension and present solutions of Maxwell equations in the internal and external
background spacetime of a magnetized spherical star in a Randall-Sundrum II
type braneworld. The star is modelled as sphere consisting of perfect highly
magnetized fluid with infinite conductivity and frozen-in dipolar magnetic
field. With respect to solutions for magnetic fields found in the Schwarzschild
spacetime brane tension introduces enhancing corrections both to the interior
and the exterior magnetic field. These corrections could be relevant for the
magnetic fields of magnetized compact objects as pulsars and magnetars and may
provide the observational evidence for the brane tension through the
modification of formula for magneto-dipolar emission which gives amplification
of electromagnetic energy loss up to few orders depending on the value of the
brane tension.Comment: 11 pages, 5 figures, 1 tabl
Quadratic Curvature Gravity with Second Order Trace and Massive Gravity Models in Three Dimensions
The quadratic curvature lagrangians having metric field equations with second
order trace are constructed relative to an orthonormal coframe. In
dimensions, pure quadratic curvature lagrangian having second order trace
constructed contains three free parameters in the most general case. The fourth
order field equations of some of these models, in arbitrary dimensions, are
cast in a particular form using the Schouten tensor. As a consequence, the
field equations for the New massive gravity theory are related to those of the
Topologically massive gravity. In particular, the conditions under which the
latter is "square root" of the former are presented.Comment: 24 pages, to appear in GR
Casimir Effect in Hyperbolic Polygons
We derive a trace formula for the spectra of quantum mechanical systems in
hyperbolic polygons which are the fundamental domains of discrete isometry
groups acting in the two dimensional hyperboloid. Using this trace formula and
the point splitting regularization method we calculate the Casimir energy for a
scalar fields in such domains. The dependence of the vacuum energy on the
number of vertexes is established.Comment: Latex, 1
Generalized exclusion and Hopf algebras
We propose a generalized oscillator algebra at the roots of unity with
generalized exclusion and we investigate the braided Hopf structure. We find
that there are two solutions: these are the generalized exclusions of the
bosonic and fermionic types. We also discuss the covariance properties of these
oscillatorsComment: 10 pages, to appear in J. Phys.
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