44195025
Subleading contributions to the black hole entropy in the brick wall approach
The brick wall model is a semiclassical approach to understand the microscopic origin of black hole entropy. In this approach, the black hole geometry is assumed to be a fixed classical background on which matter fields propagate, and the entropy of black holes supposedly arises due to the canonical entropy of matter fields outside the black hole event horizon, evaluated at the Hawking temperature. Apart from certain lower dimensional cases, the density of states of the matter fields around black holes cannot be evaluated exactly. As a result, often, in the brick wall model, the density of states and the resulting canonical entropy of the matter fields are evaluated at the leading order (in terms of ({Dirac_h}/2{pi})) in the WKB approximation. The success of the approach is reflected by the fact that the Bekenstein-Hawking area law - viz. that the entropy of black holes is equal to one-quarter the area of their event horizon, say, A{sub H} - has been recovered using this model in a variety of black hole spacetimes. In this work, we compute the canonical entropy of a quantum scalar field around static and spherically symmetric black holes through the brick wall approach at the higher ordersmore » (in fact, up to the sixth order in ({Dirac_h}/2{pi})) in the WKB approximation. We explicitly show that the brick wall model generally predicts corrections to the Bekenstein-Hawking entropy in all spacetime dimensions. In four dimensions, we find that the corrections to the Bekenstein-Hawking entropy are of the form [A{sub H}{sup n}logA{sub H}], while, in six dimensions, the corrections behave as [A{sub H}{sup m}+A{sub H}{sup n}logA{sub H}], where (m,n)<1. We compare our results with the corrections to the Bekenstein-Hawking entropy that have been obtained through the other approaches in the literature, and discuss the implications.« less
199678166
Horizon entropy and higher curvature equations of state
The Clausius relation between entropy change and heat flux has previously been used to derive Einstein's field equations as an equation of state. We examine here whether a similar derivation can be given for extensions beyond Einstein gravity to include higher derivative and higher curvature terms.
119281634
Second Law Violations in Lovelock Gravity for Black Hole Mergers
We study the classical second law of black hole thermodynamics, for Lovelock theories (other than general relativity), in arbitrary dimensions. Using the standard formula for black hole entropy, we construct scenarios involving the merger of two black holes in which the entropy instantaneously decreases. Our construction involves a Kaluza-Klein compactification down to a dimension in which one of the Lovelock terms is topological. We discuss some open issues in the definition of the second law which might be used to remove this entropy decrease.
18164758
Closed string exchanges on C2/Z2 in a background B-field
In an earlier work it was shown that the IR singularities arising in the nonplanar one loop two point function of a noncommutative = 2 gauge theory can be reproduced exactly from the massless closed string exchanges. The noncommutative gauge theory is realised on a fractional D3 brane localised at the fixed point of the C2/Z2 orbifold. In this paper we identify the contributions from each of the closed string modes. The sum of these adds up to the nonplanar two-point function.
624279
Phase Transitions in Higher Derivative Gravity
This paper deals with black holes, bubbles and orbifolds in Gauss–Bonnet theory in five dimensional anti de Sitter space. In particular, we study stable, unstable and metastable phases of black holes from thermodynamical perspective. By comparing bubble and orbifold geometries, we analyse associated instabilities. Assuming AdS/CFT correspondence, we discuss the effects of this higher derivative bulk coupling on a specific matrix model near the critical points of the boundary gauge theory at finite temperature. Finally, we propose another phenomenological model on the boundary which mimics various phases of the bulk space-time.
117009870
Energy loss due to field fluctuations in a two-stream QCD plasma
We derive the expression for the collisional energy loss in two stream plasma induced by the fluctuating chromoelectric field. It is revealed that the main contribution here comes from the unstable modes which grow exponentially with time. A strong direction dependence of the energy loss has also been demonstrated.
122369912
Interacting holographic dark energy with variable deceleration parameter and accreting black holes in Bianchi type-V universe
In this paper, we have considered the spatially homogeneous and anisotropic Bianchi type-V space time filled with two interacting fluids; dark matter and a hypothetical isotropic fluid as the holographic dark energy components. To obtain an exact solution of the Einstein’s field equations, we used the assumption of time dependent deceleration parameter. We have investigated geometric and kinematic properties of the model. It is observed that the anisotropy parameter of the universe approaches to zero and the universe achieve flatness for large cosmic time. We have shown that this expanding solution is stable against the perturbation with respect to anisotropic spatial directions. We have also studied the evolution of the mass of a black hole embedded in a universe which interacts with a combination of dark matter and dark energy, considering that in the vicinity of the black hole the metric is of Schwarzschild type. We found that the black hole mass increases with the evolution of the universe, and on later epochs the increase in mass stops as dark energy accretion takes over. The results are found to be consistent with recent cosmological observations.
110456171
Real-time dataflow and workflow with the CMS tracker data
The Tracker detector took data with cosmics rays at the Tracker Integration Facility (TIF) at CERN. First on-line monitoring tasks were executed at the Tracker Analysis Centre (TAC) which is a dedicated Control Room at TIF with limited computing resources. A set of software agents were developed to perform the real-time data conversion in a standard format, to archive data on tape at CERN and to publish them in the official CMS data bookkeeping systems. According to the CMS computing and analysis model, most of the subsequent data processing has to be done in remote Tier-1 and Tier-2 sites, so data were automatically transferred from CERN to the sites interested to analyze them, currently Fermilab, Bari and Pisa. Official reconstruction in the distributed environment was triggered in real-time by using the tool currently used for the processing of simulated events. Automatic end-user analysis of data was performed in a distributed environment, in order to derive the distributions of important physics variables. The tracker data processing is currently migrating to the Tier-0 CERN as a prototype for the global data taking chain. Tracker data were also registered into the most recent version of the data bookkeeping system, DBS-2, by profiting from the new features to handle real data. A description of the dataflow/workflow and of the tools developed is given, together with the results about the performance of the real-time chain. Almost 7.2 million events were officially registered, moved, reconstructed and analyzed in remote sites by using the distributed environment.