2,407 research outputs found
Sub-Planckian black holes and the Generalized Uncertainty Principle
The Black Hole Uncertainty Principle correspondence suggests that there could
exist black holes with mass beneath the Planck scale but radius of order the
Compton scale rather than Schwarzschild scale. We present a modified, self-dual
Schwarzschild-like metric that reproduces desirable aspects of a variety of
disparate models in the sub-Planckian limit, while remaining Schwarzschild in
the large mass limit. The self-dual nature of this solution under naturally implies a Generalized Uncertainty Principle
with the linear form . We also
demonstrate a natural dimensional reduction feature, in that the gravitational
radius and thermodynamics of sub-Planckian objects resemble that of -D
gravity. The temperature of sub-Planckian black holes scales as rather than
but the evaporation of those smaller than g is suppressed by
the cosmic background radiation. This suggests that relics of this mass could
provide the dark matter.Comment: 12 pages, 9 figures, version published in J. High En. Phy
Holographic Renormalization for Asymptotically Lifshitz Spacetimes
A variational formulation is given for a theory of gravity coupled to a
massive vector in four dimensions, with Asymptotically Lifshitz boundary
conditions on the fields. For theories with critical exponent z=2 we obtain a
well-defined variational principle by explicitly constructing two actions with
local boundary counterterms. As part of our analysis we obtain solutions of
these theories on a neighborhood of spatial infinity, study the asymptotic
symmetries, and consider different definitions of the boundary stress tensor
and associated charges. A constraint on the boundary data for the fields
figures prominently in one of our formulations, and in that case the only
suitable definition of the boundary stress tensor is due to Hollands,
Ishibashi, and Marolf. Their definition naturally emerges from our requirement
of finiteness of the action under Hamilton-Jacobi variations of the fields. A
second, more general variational principle also allows the Brown-York
definition of a boundary stress tensor.Comment: 34 pages, Added Reference
Thermodynamic instability of doubly spinning black objects
We investigate the thermodynamic stability of neutral black objects with (at
least) two angular momenta. We use the quasilocal formalism to compute the
grand canonical potential and show that the doubly spinning black ring is
thermodynamically unstable. We consider the thermodynamic instabilities of
ultra-spinning black objects and point out a subtle relation between the
microcanonical and grand canonical ensembles. We also find the location of the
black string/membrane phases of doubly spinning black objects.Comment: 25 pages, 7 figures v2: matches the published versio
Pathologies in Asymptotically Lifshitz Spacetimes
There has been significant interest in the last several years in studying
possible gravitational duals, known as Lifshitz spacetimes, to anisotropically
scaling field theories by adding matter to distort the asymptotics of an AdS
spacetime. We point out that putative ground state for the most heavily studied
example of such a spacetime, that with a flat spatial section, suffers from a
naked singularity and further point out this singularity is not resolvable by
any known stringy effect. We review the reasons one might worry that
asymptotically Lifshitz spacetimes are unstable and employ the initial data
problem to study the stability of such systems. Rather surprisingly this
question, and even the initial value problem itself, for these spacetimes turns
out to generically not be well-posed. A generic normalizable state will evolve
in such a way to violate Lifshitz asymptotics in finite time. Conversely,
enforcing the desired asymptotics at all times puts strong restrictions not
just on the metric and fields in the asymptotic region but in the deep interior
as well. Generically, even perturbations of the matter field of compact support
are not compatible with the desired asymptotics.Comment: 36 pages, 1 figure, v2: Enhanced discussion of singularity, including
relationship to Gubser's conjecture and singularity in RG flow solution, plus
minor clarification
Extended phase space thermodynamics for charged and rotating black holes and Born-Infeld vacuum polarization
We investigate the critical behaviour of charged and rotating AdS black holes
in d spacetime dimensions, including effects from non-linear electrodynamics
via the Born-Infeld action, in an extended phase space in which the
cosmological constant is interpreted as thermodynamic pressure. For
Reissner-Nordstrom black holes we find that the analogy with the Van der Walls
liquid-gas system holds in any dimension greater than three, and that the
critical exponents coincide with those of the Van der Waals system. We find
that neutral slowly rotating black holes in four space-time dimensions also
have the same qualitative behaviour. However charged and rotating black holes
in three spacetime dimensions do not exhibit critical phenomena. For
Born-Infeld black holes we define a new thermodynamic quantity B conjugate to
the Born-Infeld parameter b that we call Born-Infeld vacuum polarization. We
demonstrate that this quantity is required for consistency of both the first
law of thermodynamics and the corresponding Smarr relation.Comment: 23 pages, 32 figures, v2: minor changes, upgraded reference
Rotating black holes with equal-magnitude angular momenta in d=5 Einstein-Gauss-Bonnet theory
We construct rotating black hole solutions in Einstein-Gauss-Bonnet theory in
five spacetime dimensions. These black holes are asymptotically flat, and
possess a regular horizon of spherical topology and two equal-magnitude angular
momenta associated with two distinct planes of rotation. The action and global
charges of the solutions are obtained by using the quasilocal formalism with
boundary counterterms generalized for the case of Einstein-Gauss-Bonnet theory.
We discuss the general properties of these black holes and study their
dependence on the Gauss-Bonnet coupling constant . We argue that most
of the properties of the configurations are not affected by the higher
derivative terms. For fixed the set of black hole solutions terminates
at an extremal black hole with a regular horizon, where the Hawking temperature
vanishes and the angular momenta attain their extremal values. The domain of
existence of regular black hole solutions is studied. The near horizon geometry
of the extremal solutions is determined by employing the entropy function
formalism.Comment: 25 pages, 7 figure
Lovelock-Lifshitz Black Holes
In this paper, we investigate the existence of Lifshitz solutions in Lovelock
gravity, both in vacuum and in the presence of a massive vector field. We show
that the Lovelock terms can support the Lifshitz solution provided the
constants of the theory are suitably chosen. We obtain an exact black hole
solution with Lifshitz asymptotics of any scaling parameter in both
Gauss-Bonnet and in pure 3rd order Lovelock gravity. If matter is added in the
form of a massive vector field, we also show that Lifshitz solutions in
Lovelock gravity exist; these can be regarded as corrections to Einstein
gravity coupled to this form of matter. For this form of matter we numerically
obtain a broad range of charged black hole solutions with Lifshitz asymptotics,
for either sign of the cosmological constant. We find that these asymptotic
Lifshitz solutions are more sensitive to corrections induced by Lovelock
gravity than are their asymptotic AdS counterparts. We also consider the
thermodynamics of the black hole solutions and show that the temperature of
large black holes with curved horizons is proportional to where is
the critical exponent; this relationship holds for black branes of any size. As
is the case for asymptotic AdS black holes, we find that an extreme black hole
exists only for the case of horizons with negative curvature. We also find that
these Lovelock-Lifshitz black holes have no unstable phase, in contrast to the
Lovelock-AdS case. We also present a class of rotating Lovelock-Lifshitz black
holes with Ricci-flat horizons.Comment: 26 pages, 10 figures, a few references added, typo fixed and some
comments have been adde
Shaping black holes with free fields
Starting from a metric Ansatz permitting a weak version of Birkhoff's theorem
we find static black hole solutions including matter in the form of free scalar
and p-form fields, with and without a cosmological constant \Lambda. Single
p-form matter fields permit multiple possibilities, including dyonic solutions,
self-dual instantons and metrics with Einstein-Kaelher horizons. The inclusion
of multiple p-forms on the other hand, arranged in a homogeneous fashion with
respect to the horizon geometry, permits the construction of higher dimensional
dyonic p-form black holes and four dimensional axionic black holes with flat
horizons, when \Lambda<0. It is found that axionic fields regularize black hole
solutions in the sense, for example, of permitting regular -- rather than
singular -- small mass Reissner-Nordstrom type black holes. Their cosmic string
and Vaidya versions are also obtained.Comment: 38 pages. v2: minor changes, published versio
Gauss-Bonnet Black Holes and Heavy Fermion Metals
We consider charged black holes in Einstein-Gauss-Bonnet Gravity with
Lifshitz boundary conditions. We find that this class of models can reproduce
the anomalous specific heat of condensed matter systems exhibiting
non-Fermi-liquid behaviour at low temperatures. We find that the temperature
dependence of the Sommerfeld ratio is sensitive to the choice of Gauss-Bonnet
coupling parameter for a given value of the Lifshitz scaling parameter. We
propose that this class of models is dual to a class of models of
non-Fermi-liquid systems proposed by Castro-Neto et.al.Comment: 17 pages, 6 figures, pdfLatex; small corrections to figure 10 in this
versio
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