Thermodynamics and evaporation of the noncommutative black hole

We investigate the thermodynamics of the noncommutative black hole whose static picture is similar to that of the nonsingular black hole known as the de Sitter-Schwarzschild black hole. It turns out that the final remnant of extremal black hole is a thermodynamically stable object. We describe the evaporation process of this black hole by using the noncommutativity-corrected Vaidya metric. It is found that there exists a close relationship between thermodynamic approach and evaporation process.Comment: 16 pages, 6 figures, added references, to appear in JHE

Thermodynamics of Gauss-Bonnet black holes revisited

We investigate the Gauss-Bonnet black hole in five dimensional anti-de Sitter spacetimes (GBAdS). We analyze all thermodynamic quantities of the GBAdS, which is characterized by the Gauss-Bonnet coupling $c$ and mass $M$, comparing with those of the Born-Infeld-AdS (BIAdS), Reissner-Norstr\"om-AdS black holes (RNAdS), Schwarzschild-AdS (SAdS), and BTZ black holes. For $c<0$ we cannot obtain the black hole with positively definite thermodynamic quantities of mass, temperature, and entropy because the entropy does not satisfy the area-law. On the other hand, for $c>0$, we find the BIAdS-like black hole, showing that the coupling $c$ plays the role of pseudo-charge. Importantly, we could not obtain the SAdS in the limits of $c\to 0$, which means that the GBAdS is basically different from the SAdS. In addition, we clarify the connections between thermodynamic and dynamical stability. Finally, we also conjecture that if a black hole is big and thus globally stable, its quasinormal modes may take analytic expressions.Comment: 22 pages, 8 figures, version to appear in EPJ

Scattering from an AdS_3 bubble and an exact AdS_3

We investigate the close relationship between the potential and absorption cross section for test fields in an AdS$_3$ bubble(a 5D black hole) and an exact AdS$_3$. There are two solutions in type IIB string theory: an AdS$_3$ bubble corresponds to the dilatonic solution, while an exact AdS$_3$ is the non-dilatonic solution. In order to obtain the cross section for an AdS$_3$ bubble, we introduce the \{out\}-state scattering picture with the AdS$_3$-AFS matching procedure. For an exact AdS$_3$, one considers the \{in\}-state scattering picture with the AdS$_3$-AdS$_3$ matching. Here the non-normalizable modes are crucially taken into account for the matching procedure. It turns out that the cross sections for the test fields in an AdS$_3$ bubble take the same forms as those in an exact AdS$_3$. This suggests that in the dilute gas and the low energy limits, the S-matrix for an AdS$_3$ bubble can be derived from an exact AdS$_3$ space.Comment: revised version to appear in Physical Review D, 26 pages with embedded 5 EPS figures in RevTex forma

Rotating Black Branes in the presence of nonlinear electromagnetic field

In this paper, we consider a class of gravity whose action represents itself as a sum of the usual Einstein-Hilbert action with cosmological constant and an $U(1)$ gauge field for which the action is given by a power of the Maxwell invariant. We present a class of the rotating black branes with Ricci flat horizon and show that the presented solutions may be interpreted as black brane solutions with two event horizons, extreme black hole and naked singularity provided the parameters of the solutions are chosen suitably. We investigate the properties of the solutions and find that for the special values of the nonlinear parameter, the solutions are not asymptotically anti-deSitter. At last, we obtain the conserved quantities of the rotating black branes and find that the nonlinear source effects on the electric field, the behavior of spacetime, type of singularity and other quantities.Comment: 7 pages, 5 figures, to appear in EPJ

dS-Holographic C-Functions with a Topological, Dilatonic Twist

Recently, the holographic aspects of asymptotically de Sitter spacetimes have generated substantial literary interest. The plot continues in this paper, as we investigate a certain class of dilatonically deformed ``topological'' de Sitter solutions (which were introduced in hep-th/0110234). Although such solutions possess a detrimental cosmological singularity, their interpretation from a holographic perspective remains somewhat unclear. The current focus is on the associated generalized $C$-functions, which are shown to maintain their usual monotonicity properties in spite of this exotic framework. These findings suggest that such topological solutions may still play a role in our understanding of quantum gravity with a positive cosmological constant.Comment: Latex, 30 pages; reference added and minor changes to tex

Thermodynamics of higher dimensional topological charged AdS black branes in dilaton gravity

In this paper, we study topological AdS black branes of $(n+1)$-dimensional Einstein-Maxwell-dilaton theory and investigate their properties. We use the area law, surface gravity and Gauss law interpretations to find entropy, temperature and electrical charge, respectively. We also employ the modified Brown and York subtraction method to calculate the quasilocal mass of the solutions. We obtain a Smarr-type formula for the mass as a function of the entropy and the charge, compute the temperature and the electric potential through the Smarr-type formula and show that these thermodynamic quantities coincide with their values which are calculated through using the geometry. Finally, we perform a stability analysis in the canonical ensemble and investigate the effects of the dilaton field and the size of black brane on the thermal stability of the solutions. We find that large black branes are stable but for small black brane, depending on the value of dilaton field and type of horizon, we encounter with some unstable phases.Comment: 21 pages, 21 figures, references updated, minor editing, accepted in EPJC (DOI: 10.1140/epjc/s10052-010-1483-3

Challenges and Obstacles for a Bouncing Universe in Brane Models

A Brane evolving in the background of a charged AdS black-hole displays in general a bouncing behaviour with a smooth transition from a contracting to an expanding phase. We examine in detail the conditions and consequences of this behaviour in various cases. For a cosmological-constant-dominated Brane, we obtain a singularity-free, inflationary era which is shown to be compatible only with an intermediate-scale fundamental Planck mass. For a radiation-dominated Brane, the bouncing behaviour can occur only for background-charge values exceeding those allowed for non-extremal black holes. For a matter-dominated Brane, the black-hole mass affects the proper volume or the expansion rate of the Brane. We also consider the Brane evolving in an asymmetric background of two distinct charged AdS black hole spacetimes being bounded by the Brane and find that, in the case of an empty critical Brane, bouncing behaviour occurs only if the black-hole mass difference is smaller than a certain value. The effects of a Brane curvature term on the bounce at early and late times are also investigated.Comment: 23 pages, Latex file, comments and references added, version to appear in Phys. Rev.