23,332 research outputs found
Massless scalar fields and topological black holes
The exact static solutions in the higher dimensional Einstein-Maxwell-Klein-
Gordon theory are investigated. With the help of the methods developed for the
effective dilaton type gauge gravity models in two dimensions, we find new
spherically and hyperbolically symmetric solutions which generalize the four
dimensional configurations of Dereli-Eris. We show that, like in four
dimensions, the non-trivial scalar field yields, in general, a naked
singularity. The new solutions are compared with the higher dimensional
Brans-Dicke black hole type solutions.Comment: 15 pages, LATEX, no figures. (To appear in Phys. Rev. D
Effective spatial dimension of extremal non-dilatonic black p-branes and the description of entropy on the world volume
By investigating the critical behavior appearing at the extremal limit of the
non-dilatonic, black p-branes in (d+p) dimensions, we find that some critical
exponents related to the critical point obey the scaling laws. From the scaling
laws we obtain that the effective spatial dimension of the non-dilatonic black
holes and black strings is one, and is p for the non-dilatonic black p-branes.
For the dilatonic black holes and black p-branes, the effective dimension will
depend on the parameters in theories. Thus, we give an interpretation why the
Bekenstein-Hawking entropy may be given a simple world volume interpretation
only for the non-dilatonic black p-branes.Comment: 4 pages, RevTex, no figures, to appear in Phys. Rev. Let
Thermodynamical properties of the Universe with dark energy
We have investigated the thermodynamical properties of the Universe with dark
energy. Adopting the usual assumption in deriving the constant co-moving
entropy density that the physical volume and the temperature are independent,
we observed some strange thermodynamical behaviors. However, these strange
behaviors disappeared if we consider the realistic situation that the physical
volume and the temperature of the Universe are related. Based on the well known
correspondence between the Friedmann equation and the first law of
thermodynamics of the apparent horizon, we argued that the apparent horizon is
the physical horizon in dealing with thermodynamics problems. We have
concentrated on the volume of the Universe within the apparent horizon and
considered that the Universe is in thermal equilibrium with the Hawking
temperature on the apparent horizon. For dark energy with , the
holographic principle and the generalized second law are always respected.Comment: two figures; v2: minor corrections and updates, JCAP in pres
Critical behavior in 2+1 dimensional black holes
The critical behavior and phase transition in the 2+1 dimensional Ba\~nados,
Teitelboim, and Zanelli (BTZ) black holes are discussed. By calculating the
equilibrium thermodynamic fluctuations in the microcanonical ensemble,
canonical ensemble, and grand canonical ensemble, respectively, we find that
the extremal spinning BTZ black hole is a critical point, some critical
exponents satisfy the scaling laws of the ``first kind'', and the scaling laws
related to the correlation length suggest that the effective spatial dimension
of extremal black holes is one, which is in agreement with the argument that
the extremal black holes are the Bogomol'nyi saturated string states. In
addition, we find that the massless BTZ black hole is a critical point of
spinless BTZ black holes.Comment: RevTex, 9 pages, nofigur
Relationship between five-dimensional black holes and de Sitter spaces
We study a close relationship between the topological anti-de Sitter
(TAdS)-black holes and topological de Sitter (TdS) spaces including the
Schwarzschild-de Sitter (SdS) black hole in five-dimensions. We show that all
thermal properties of the TdS spaces can be found from those of the TAdS black
holes by replacing by . Also we find that all thermal information for
the cosmological horizon of the SdS black hole is obtained from either the
hyperbolic-AdS black hole or the Schwarzschild-TdS space by substituting
with . For this purpose we calculate thermal quantities of bulk,
(Euclidean) conformal field theory (ECFT) and moving domain wall by using the
A(dS)/(E)CFT correspondences. Further we compute logarithmic corrections to the
Bekenstein-Hawking entropy, Cardy-Verlinde formula and Friedmann equation due
to thermal fluctuations. It implies that the cosmological horizon of the TdS
spaces is nothing but the event horizon of the TAdS black holes and the dS/ECFT
correspondence is valid for the TdS spaces in conjunction with the AdS/CFT
correspondence for the TAdS black holes.Comment: 17 page
Black holes in the Brans-Dicke-Maxwell theory
The black hole solutions in the higher dimensional Brans-Dicke-Maxwell theory
are investigated. We find that the presence of the nontrivial scalar field
depends on the spacetime dimensions (D). When D=4, the solution corresponds to
the Reissner-Nordstr\"{o}m black hole with a constant scalar field. In higher
dimensions (D>4), one finds the charged black hole solutions with the
nontrivial scalar field. The thermal properties of the charged black holes are
discussed and the reason why the nontrivial scalar field exists are explained.
Also the solutions for higher dimensional Brans-Dicke theory are given for
comparison.Comment: Revtex, 5 pages, no figures, contents were rewritten and new
references were adde
Examining exotic structure of proton-rich nucleus Al
The longitudinal momentum distribution (P_{//}) of fragments after one-proton
removal from ^{23} Al and reaction cross sections (\sigma_R) for
^{23,24} Al on carbon target at 74A MeV have been measured. The ^{23,24} Al
ions were produced through projectile fragmentation of 135 A MeV ^{28} Si
primary beam using RIPS fragment separator at RIKEN. P_{//} is measured by a
direct time-of-flight (TOF) technique, while \sigma_R is determined using a
transmission method. An enhancement in \sigma_R is observed for ^{23} Al
compared with ^{24} Al. The P_{//} for ^{22} Mg fragments from ^{23} Al breakup
has been obtained for the first time. FWHM of the distributions has been
determined to be 232 \pm 28 MeV/c. The experimental data are discussed by using
Few-Body Glauber model. Analysis of P_{//} demonstrates a dominant d-wave
configuration for the valence proton in ground state of ^{23} Al, indicating
that ^{23} Al is not a proton halo nucleus
Thermodynamic Properties of Spherically-Symmetric, Uniformly-Accelerated Reference Frames
We aim to study the thermodynamic properties of the spherically symmetric
reference frames with uniform acceleration, including the spherically symmetric
generalization of Rindler reference frame and the new kind of uniformly
accelerated reference frame. We find that, unlike the general studies about the
horizon thermodynamics, one cannot obtain the laws of thermodynamics for their
horizons in the usual approaches, despite that one can formally define an area
entropy (Bekenstein-Hawking entropy). In fact, the common horizon for a set of
uniformly accelerated observers is not always exist, even though the
Hawking-Unruh temperature is still well-defined. This result indicates that the
Hawking-Unruh temperature is only a kinematic effect, to gain the laws of
thermodynamics for the horizon, one needs the help of dynamics. Our result is
in accordance with those from the various studies about the acoustic black
holes.Comment: 8 page
On the topology and area of higher dimensional black holes
Over the past decade there has been an increasing interest in the study of
black holes, and related objects, in higher (and lower) dimensions, motivated
to a large extent by developments in string theory. The aim of the present
paper is to obtain higher dimensional analogues of some well known results for
black holes in 3+1 dimensions. More precisely, we obtain extensions to higher
dimensions of Hawking's black hole topology theorem for asymptotically flat
() black hole spacetimes, and Gibbons' and Woolgar's genus
dependent, lower entropy bound for topological black holes in asymptotically
locally anti-de Sitter () spacetimes. In higher dimensions the genus
is replaced by the so-called -constant, or Yamabe invariant, which is a
fundamental topological invariant of smooth compact manifolds.Comment: 15 pages, Latex2e; typos corrected, a convention clarified, resulting
in the simplification of certain formulas, other improvement
Hologrphy and holographic dark energy model
The holographic principle is used to discuss the holographic dark energy
model. We find that the Bekenstein-Hawking entropy bound is far from saturation
under certain conditions. A more general constraint on the parameter of the
holographic dark energy model is also derived.Comment: no figures, use revtex, v2: use iop style, some typos corrected and
references updated, will appear in CQ
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