15 research outputs found
Thermodynamics of Rotating Black Branes in Gauss-Bonnet-Born-Infeld Gravity
Considering both the Gauss-Bonnet and the Born-Infeld terms, which are on
similar footing with regard to string corrections on the gravity side and
electrodynamic side, we present a new class of rotating solutions in
Gauss-Bonnet gravity with rotation parameters in the presence of a
nonlinear electromagnetic field. These solutions, which are asymptotically
anti-de Sitter in the presence of cosmological constant, may be interpreted as
black brane solutions with inner and outer event horizons, an extreme black
brane or naked singularity provided the metric parameters are chosen suitably.
We calculate the finite action and conserved quantities of the solutions by
using the counterterm method, and find that these quantities do not depend on
the Gauss-Bonnet parameter. We also compute the temperature, the angular
velocities, the electric charge and the electric potential. Then, we calculate
the entropy of the black brane through the use of Gibbs-Duhem relation and show
that it obeys the area law of entropy. We obtain a Smarr-type formula for the
mass as a function of the entropy, the angular momenta and the charge, and show
that the conserved and thermodynamic quantities satisfy the first law of
thermodynamics. Finally, we perform a stability analysis in both the canonical
and grand-canonical ensemble and show that the presence of a nonlinear
electromagnetic field has no effect on the stability of the black branes, and
they are stable in the whole phase space.Comment: 17 pages, one figur
Effect of Freestream Turbulence on Roughness-induced Crossflow Instability
AbstractThe effect of freestream turbulence on generation of crossflow disturbances over swept wings is investigated through direct nu- merical simulations. The set up follows the experiments performed by Downs et al. (2012). In these experiments the authors use ASU(67)-0315 wing geometry which promotes growth of crossflow disturbances. Distributed roughness elements are locally placed near the leading edge with a given spanwise wavenumber to excite the corresponding stationary crossflow vortices. In present study, we partially reproduce the isotropic homogenous freestream turbulence through direct numerical simulations using freestream spectrum data from the experiments. The generated freestream fields are then applied as the inflow boundary condition for direct numerical simulation of the wing. The distributed roughness elements are modelled through wing surface deformation and placed near the leading edge to trigger the stationary crossflow disturbances. The effects of the generated freestream turbulence on the initial amplitudes and growth of the boundary layer perturbations are then studied
Vertex Operators in Background with NS_NS Flux using Berkovits-Vafa-Witten Variables
String equations for the vertex operators of type IIB on
background with NS-NS flux are calculated using Berkovits-Vafa-Witten
formalism. With suitable field definitions, the linearized field equations for
six-dimensional supergravity and a tensor multiplet on are
recovered from these. We also discuss the massless degrees of freedom that
survive the Kaluza-Klein compactification and how our vertex operators
are related to the vertex operators introduced by Giveon, Kutasov and Seiberg.Comment: 14 pages, LaTeX, added new reference
Thermodynamics of a Kerr Newman de Sitter Black Hole
We compute the conserved quantities of the four-dimensional Kerr-Newman-dS
(KNdS) black hole through the use of the counterterm renormalization method,
and obtain a generalized Smarr formula for the mass as a function of the
entropy, the angular momentum and the electric charge. The first law of
thermodynamics associated to the cosmological horizon of KNdS is also
investigated. Using the minimal number of intrinsic boundary counterterms, we
consider the quasilocal thermodynamics of asymptotic de Sitter
Reissner-Nordstrom black hole, and find that the temperature is equal to the
product of the surface gravity (divided by ) and the Tolman redshift
factor. We also perform a quasilocal stability analysis by computing the
determinant of Hessian matrix of the energy with respect to its thermodynamic
variables in both the canonical and the grand-canonical ensembles and obtain a
complete set of phase diagrams. We then turn to the quasilocal thermodynamics
of four-dimensional Kerr-Newman-de Sitter black hole for virtually all possible
values of the mass, the rotation and the charge parameters that leave the
quasilocal boundary inside the cosmological event horizon, and perform a
quasilocal stability analysis of KNdS black hole.Comment: REVTEX4, 12 pages, 12 figures, references added and some points in
Sec II have been clarified, version to appear in Can. J. Phy
Entropy of Rotating Misner String Spacetimes
Using a boundary counterterm prescription motivated by the AdS/CFT
conjecture, I evaluate the energy, entropy and angular momentum of the class of
Kerr-NUT/bolt-AdS spacetimes. As in the non-rotating case, when the NUT charge
is nonzero the entropy is no longer equal to one-quarter of the area due to the
presence of the Misner string. When the cosmological constant is also non-zero,
the entropy is bounded from above.Comment: Revtex, 9 pages, 3 figure
Kerr de Sitter Spacetimes in Various Dimension and dS/CFT Correspondence
We consider the Kerr-de Sitter (Kerr-dS) black hole in various dimensions.
Introducing a counterterm, we show that the total action of these spacetimes
are finite. We compute the masses and the angular momenta of Kerr-dS spaces
with one rotational parameter in four, five and seven dimensions. These
conserved charges are also computed for the case of Kerr-dS space with two
rotational parameters in five dimensions. Although the angular momentum density
due to the counterterm is nonzero, it gives a vanishing contribution to the
total angular momentum. We also find that the total angular momentum of the
spacetime is independent of the radius of the boundary for all cases, a fact
that is not true for the total mass of the system.Comment: 11 pages, no figure, reference added, the version to be published in
Phys. Rev. D6
Misner String Entropy
I show that gravitational entropy can be ascribed to spacetimes containing
Misner strings (the gravitational analogues of Dirac strings), even in the
absence of any other event horizon (or bolt) structures. This result follows
from an extension of proposals for evaluating the stress-energy of a
gravitational system which are motivated by the AdS/CFT correspondence.Comment: revtex, 5 pages, references added, typo correcte
Quasilocal Thermodynamics of Kerr and Kerr-anti-de Sitter Spacetimes and the AdS/CFT Correspondence
We consider the quasilocal thermodynamics of rotating black holes in
asymptotically flat and asymptotically anti de Sitter spacetimes. Using the
minimal number of intrinsic boundary counterterms inspired by the AdS/CFT
correspondence, we find that we are able to carry out an analysis of the
thermodynamics of these black holes for virtually all possible values of the
rotation parameter and cosmological constant that leave the quasilocal boundary
well-defined, going well beyond what is possible with background subtraction
methods. Specifically, we compute the quasilocal energy and angular
momentum for arbitrary values of the rotation, mass and cosmological
constant parameters for the 3+1 dimensional Kerr, Kerr-AdS black holes and 2+1
dimensional BTZ black hole. We perform a quasilocal stability analysis and find
phase behavior that is commensurate with previous analyses carried out at
infinity.Comment: Latex, 43 pages, 22 eps figures, several typos corrected, final
version to appear in Phys. Rev.
Ricci flat rotating black branes with a conformally invariant Maxwell source
We consider Einstein gravity coupled to an gauge field for which the
density is given by a power of the Maxwell Lagrangian. In -dimensions the
action of Maxwell field is shown to enjoy the conformal invariance if the power
is chosen as . We present a class of charge rotating solutions in
Einstein-conformally invariant Maxwell gravity in the presence of a
cosmological constant. These solutions may be interpreted as black brane
solutions with inner and outer event horizons or an extreme black brane
depending on the value of the mass parameter. Since we are considering power of
the Maxwell density, the black brane solutions exist only for dimensions which
are multiples of four. We compute conserved and thermodynamics quantities of
the black brane solutions and show that the expression of the electric field
does not depend on the dimension. Also, we obtain a Smarr-type formula and show
that these conserved and thermodynamic quantities of black branes satisfy the
first law of thermodynamics. Finally, we study the phase behavior of the
rotating black branes and show that there is no Hawking--Page phase transition
in spite of conformally invariant Maxwell field.Comment: 13 pages, one figur
3D Gravity, Point Particles and Liouville Theory
This paper elaborates on the bulk/boundary relation between negative
cosmological constant 3D gravity and Liouville field theory (LFT). We develop
an interpretation of LFT non-normalizable states in terms of particles moving
in the bulk. This interpretation is suggested by the fact that ``heavy'' vertex
operators of LFT create conical singularities and thus should correspond to
point particles moving inside AdS. We confirm this expectation by comparing the
(semi-classical approximation to the) LFT two-point function with the
(appropriately regularized) gravity action evaluated on the corresponding
metric.Comment: 17 pages, 3 figures, references adde