1,739 research outputs found
Acoustic black holes: massless scalar field analytic solutions and analogue Hawking radiation
We obtain the analytic solutions of the radial part of the massless
Klein-Gordon equation in the spacetime of both three dimensional rotating and
four dimensional canonical acoustic black holes, which are given in terms of
the confluent Heun functions. From these solutions, we obtain the scalar waves
near the acoustic horizon. We discuss the analogue Hawking radiation of
massless scalar particles and the features of the spectrum associated with the
radiation emitted by these acoustic black holes.Comment: 26 pages, with erratum. arXiv admin note: text overlap with
arXiv:1405.784
Lagrangian formulation of Newtonian cosmology
In this paper, we use the Lagrangian formalism of classical mechanics and
some assumptions to obtain cosmological differential equations analogous to
Friedmann and Einstein equations, obtained from the theory of general
relativity. This method can be used to a universe constituted of incoherent
matter, that is, the cosmologic substratum is comprised of dust.Comment: 5 pages. accepted for publication in Revista Brasileira de Ensino de
F\'{i}sica (RBEF). arXiv admin note: text overlap with arXiv:astro-ph/0309756
by other author
Confluent Heun functions and the physics of black holes: resonant frequencies, Hawking radiation and scattering of scalar waves
We apply the confluent Heun functions to study the resonant frequencies
(quasispectrum), the Hawking radiation and the scattering process of scalar
waves, in a class of spacetimes, namely, the ones generated by a
Kerr-Newman-Kasuya spacetime (dyon black hole) and a Reissner-Nordstr\"{o}m
black hole surrounded by a magnetic field (Ernst spacetime). In both
spacetimes, the solutions for the angular and radial parts of the corresponding
Klein-Gordon equations are obtained exactly, for massive and massless fields,
respectively. The special cases of Kerr and Schwarzschild black holes are
analyzed and the solutions obtained, as well as in the case of a Schwarzschild
black hole surrounded by a magnetic field. In all these special situations, the
resonant frequencies, Hawking radiation and scattering are studied.Comment: 18 pages. This paper was unified and published with arXiv:1603.0224
Class of solutions of the Wheeler-DeWitt equation in the Friedmann-Robertson-Walker universe
We show that the solutions of the Wheeler-DeWitt equation in a homogeneous
and isotropic universe are given by triconfluent Heun functions for the
spatially closed, flat, and open geometries of the Friedmann-Robertson-Walker
universe filled with different forms of energy. In a matter-dominated universe,
we find the polynomial solution and the energy density spectrum. In the cases
of radiation-dominated and vacuum universes, there are no polynomial solutions
as shown.Comment: 20 pages, 10 figure
Quantum Newtonian cosmology and the biconfluent Heun functions
We obtain the exact solution of the Schr\"odinger equation for a particle
(galaxy) moving in a Newtonian universe with a cosmological constant, which is
given in terms of the biconfluent Heun functions. The first six Heun
polynomials of the biconfluent function are written explicitly. The energy
spectrum which resembles the one corresponding to the isotropic harmonic
oscillator is also obtained. The wave functions as well as the energy levels
codify the role played by the cosmological constant.Comment: 15 pages, 2 figure
Ground State Energy of Massive Scalar Field in the Global Monopole Background
We consider the ground state energy of scalar massive field in the spacetime
of a pointlike global monopole. Using zeta function regularization method we
obtain the heat kernel coefficients for this system. We show that the
coefficient contains additional contribution due to the non-trivial
topological structure of the spacetime. Taking into account the heat kernel
coefficients we obtain that the ground state energy of the scalar field is
zero. We also discuss our result using dimensional considerations.Comment: 8 pages, RevTex, no figure
On the extension of Jackiw's scalar theory to (2+1)- dimensional gravity
We study some aspects of three-dimensional gravity by extending Jackiw's
scalar theory to (2+1)-dimensions and find a black hole solution. We show that
in in general this teory does not possess a Newtonian limit except for special
metric configurations.Comment: 11 pages, LATEX fil
Remarks on some quantum effects in the spacetime of a cosmic string
We study the behaviour of a non-relativistic quantum particle interacting
with different potentials, in the background spacetime generated by a cosmic
string. We find the energy spectra for the quantum systems under consideration
and discuss how they differ from their flat Minkowski spacetime values.Comment: 17 pages, LATEX fil
Analytic solutions in the dyon black hole with a cosmic string: scalar fields, Hawking radiation and energy flux
Charged massive scalar fields are considered in the gravitational and
electromagnetic field produced by a dyonic black hole with a cosmic string
along its axis of symmetry. Exact solutions of both angular and radial parts of
the covariant Klein-Gordon equation in this background are obtained, and are
given in terms of the confluent Heun functions. The role of the presence of the
cosmic string in these solutions is showed up. From the radial solution, we
obtain the exact wave solutions near the exterior horizon of the black hole,
and discuss the Hawking radiation spectrum and the energy flux.Comment: 21 pages. arXiv admin note: substantial text overlap with
arXiv:1405.7846, arXiv:1401.5397, arXiv:1406.688
Hydrogen atom in the gravitational fields of topological defects
We consider a hydrogen atom in the background spacetimes generated by an
infinitely thin cosmic string and by a point-like global monopole. In both
cases, we find the solutions of the corresponding Dirac equations and we
determine the energy levels of the atom. We investigate how the geometric and
topological features of these spacetimes leads to shifts in the energy levels
as compared with the flat Minkowski spacetime.Comment: 17 pages, LATEX fil
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