3,538 research outputs found
Rate of decoherence for an electron weakly coupled to a phonon gas
We study the dynamics of an electron weakly coupled to a phonon gas. The
initial state of the electron is the superposition of two spatially localized
distant bumps moving towards each other, and the phonons are in a thermal
state. We investigate the dynamics of the system in the kinetic regime and show
that the time evolution makes the non-diagonal terms of the density matrix of
the electron decay, destroying the interference between the two bumps. We show
that such a damping effect is exponential in time, and the related decay rate
is proportional to the total scattering cross section of the electron-phonon
interaction.Comment: 27 pages, 2 figure
Black hole conserved charges in Generalized Minimal Massive Gravity
In this paper we construct mass, angular momentum and entropy of black hole
solution of Generalized Minimal Massive Gravity (GMMG) in asymptotically
Anti-de Sitter (AdS) spacetimes. The generalized minimal massive gravity theory
is realized by adding the CS deformation term, the higher derivative
deformation term, and an extra term to pure Einstein gravity with a negative
cosmological constant. We apply our result for conserved charge to the rotating BTZ black hole solution of GMMG, and find energy,
angular momentum and entropy. Then we show our results for these quantities are
consistent with the first law of black holes thermodynamics.Comment: 11 pages, accepted for publication in PLB. arXiv admin note: text
overlap with arXiv:1412.215
Lorentz-diffeomorphism Conserved Charges And Virasoro Algebra In Chern-Simons-Like Theories Of Gravity
The Chern-Simons-like theories of gravity (CSLTG) are formulated at first
order formalism. In this formalism, the derivation of the entropy of a black
hole on bifurcation surface, as a quasi-local conserved charge is problematic.
In this paper we overcome to these problems by considering the concept of total
variation and the Lorentz-Lie derivative. We firstly find an expression for the
ADT conserved current in the context of the CSLTG which is based on the concept
of the Killing vector fields. Then, we generalize it to be conserved for all
diffeomorphism generators. Thus, we can extract an off-shell conserved charge
for any vector field which generates a diffeomorphism. The formalism presented
here is based on the concept of quasi-local conserved charges which are
off-shell. The charges can be calculated on any codimension two space-like
surface surrounding a black hole and the results are independent of the chosen
surface. By using the off-shell quasi-local conserved charge, we investigate
the Virasoro algebra and find a formula to calculate the central extension
term. We apply the formalism to the BTZ black hole solution in the context of
the Einstein gravity and the Generalized massive gravity, then we find the
eigenvalues of their Virasoro generators as well as the corresponding central
charges. Eventually, we calculate the entropy of the BTZ black hole by the
Cardy formula and we show that the result exactly matches with the one obtained
by the concept of the off-shell conserved charges.Comment: 19 pages. In Press by Nucl. Phys. B (2016).
doi:10.1016/j.nuclphysb.2016.05.02
Black hole entropy in the Chern-Simons-like theories of gravity and Lorentz-diffeomorphism Noether charge
In the first order formalism of gravity theories, there are some theories
which are not Lorentz-diffeomorphism covariant. In the framework of such
theories we cannot apply the method of conserved charge calculation used in
Lorentz-diffeomorphism covariant theories. In this paper we firstly introduce
the total variation of a quantity due to an infinitesimal
Lorentz-diffeomorphism transformation. Secondly, in order to obtain the
conserved charges of Lorentz-diffeomorphism non-covariant theories, we extend
the Tachikawa method \cite{3}. This extension includes not only Lorentz gauge
transformation but also the diffeomorphism. We apply this method to the
Chern-Simons-like theories of gravity (CSLTG) and obtain a general formula for
the entropy of black holes in those theories. Finally, some examples on CSLTG
are provided and the entropy of the BTZ black hole is calculated in the context
of the examples.Comment: 13 pages, we have improved language of the pape
Enhanced asymptotic algebra of the flat spacetime solutions of generalized minimal massive gravity
We apply the new fall of conditions presented in the paper \cite{10} on
asymptotically flat spacetime solutions of Chern-Simons-like theories of
gravity. We show that the considered fall of conditions asymptotically solve
equations of motion of generalized minimal massive gravity. We demonstrate that
there exist two type of solutions, one of those is trivial and the others are
non-trivial. By looking at non-trivial solutions, for asymptotically flat
spacetimes in the generalized minimal massive gravity, in contrast to Einstein
gravity, cosmological parameter can be non-zero. We obtain the conserved
charges of the asymptotically flat spacetimes in generalized minimal massive
gravity, and by introducing Fourier modes we show that the asymptotic symmetry
algebra is a semidirect product of a algebra and two current
algebras. Also we verify that the algebra can be obtained by a
contraction of the AdS asymptotic symmetry algebra when the AdS radius
tends to infinity in the flat-space limit. Finally we find energy, angular
momentum and entropy for a particular case and deduce that these quantities
satisfy the first law of flat space cosmologies.Comment: 16 pages. arXiv admin note: text overlap with arXiv:1701.0020
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