1,218 research outputs found
Configurational entropy of charged AdS black holes
When we consider charged AdS black holes in higher dimensional spacetime and
a molecule number density along coexistence curves is numerically extended to
higher dimensional cases. It is found that a number density difference of a
small and large black holes decrease as a total dimension grows up. In
particular, we find that a configurational entropy is a concave function of a
reduced temperature and reaches a maximum value at a critical (second-order
phase transition) point. Furthermore, the bigger a total dimension becomes, the
more concave function in a configurational entropy while the more convex
function in a reduced pressure.Comment: 6 pages, 4 figures, typos corrected, version to appear in PL
The Extended Thermodynamic Properties of a topological Taub-NUT/Bolt-AdS spaces
We consider higher dimensional topological Taub-NUT/Bolt-AdS solutions where
a cosmological constant is treated as a pressure. The thermodynamic quantities
of these solutions are explicitly calculated. Furthermore, we find these
thermodynamic quantities satisfy the Clapeyron equation. In particular, a new
thermodynamically stable region for the NUT solution is found by studying the
Gibbs free energy. Intriguingly, we also find that like the AdS black hole
case, the G-T diagram of the Bolt solution has two branches which are joined at
a minimum temperature. The Bolt solution with the large radius, at the lower
branch, becomes stable beyond a certain temperature while the Bolt solution
with the small radius, at the upper branch, is always unstable.Comment: 7 pages, 6 figures, typos corrected, version to appear in PL
The Extended Thermodynamic Properties of Taub-NUT/Bolt-AdS spaces
We investigate the extended thermodynamic properties of higher-dimensional
Taub-NUT/Bolt-AdS spaces where a cosmological constant is treated as a
pressure. We find a general form for thermodynamic volumes of Taub-NUT/Bolt-AdS
black holes for arbitrary dimensions. Interestingly, it is found that the
Taub-NUT-AdS metric has a thermodynamically stable range when the total number
of dimensions is a multiple of 4 (4, 8, 12, ...). We also explore their phase
structure and find the first order phase transition holds for
higher-dimensional cases.Comment: 18 pages, 5 figures, typos corrected, references added, version to
appear in PL
Late Time Behaviors of an Inhomogeneous Rolling Tachyon
We study an inhomogeneous decay of an unstable D-brane in the context of
Dirac-Born-Infeld~(DBI)-type effective action. We consider tachyon and
electromagnetic fields with dependence of time and one spatial coordinate, and
an exact solution is found under an exponentially decreasing tachyon potential,
, which is valid for the description of the late time
behavior of an unstable D-brane. Though the obtained solution contains both
time and spatial dependence, the corresponding momentum density vanishes over
the entire spacetime region. The solution is governed by two parameters. One
adjusts the distribution of energy density in the inhomogeneous direction, and
the other interpolates between the homogeneous rolling tachyon and static
configuration. As time evolves, the energy of the unstable D-brane is converted
into the electric flux and tachyon matter.Comment: 17 pages, 1 figure, version to appear in PR
Configurational entropy of tachyon kinks on unstable Dp-branes
We consider tachyon effective theory with Born-Infeld electromagnetic fields
and investigate the configurational entropy of the various tachyon kink
solutions. We find that the configurational entropy stats at a minimum value
and saturates to a maximum value as the negative pressure of pure tachyonic
field increases. In particular, when an electric field is turned on and its
magnitude is larger than or equal to the critical value, we find the
configurational entropy has a global minimum, which is related to the
predominant tachyonic states.Comment: 9 pages, 20 figures, typos corrected, added comments and references,
version to appear in PL
Quasi-Normal Modes of a Natural AdS Wormhole in Einstein-Born-Infeld Gravity
We study the matter perturbations of a new AdS wormhole in (3+1)-dimensional
Einstein-Born-Infeld gravity, called "natural wormhole", which does not require
exotic matters. We discuss the stability of the perturbations by numerically
computing the quasi-normal modes (QNMs) of a massive scalar field in the
wormhole background. We investigate the dependence of quasi-normal frequencies
on the mass of scalar field as well as other parameters of the wormhole. It is
found that the perturbations are always stable for the wormhole geometry which
has the general relativity (GR) limit when the scalar field mass m satisfies a
certain, tachyonic mass bound m^2 > m^2_* with m^2_* < 0, analogous to the
Breitenlohner-Freedman (BF) bound in the global-AdS space, m^2_BF = 3 Lambda/4.
It is also found that the BF-like bound m^2_* shifts by the changes of the
cosmological constant Lambda or angular-momentum number l, with a level
crossing between the lowest complex and pure-imaginary modes for zero angular
momentum l = 0. Furthermore, it is found that the unstable modes can also have
oscillatory parts as well as non-oscillatory parts depending on whether the
real and imaginary parts of frequencies are dependent on each other or not,
contrary to arguments in the literature. For wormhole geometries which do not
have the GR limit, the BF-like bound does not occur and the perturbations are
stable for arbitrary tachyonic and non-tachyonic masses, up to a critical mass
m^2_c > 0 where the perturbations are completely frozen.Comment: Added comments and references, Accepted in EPJ
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