63 research outputs found
Fermion localization on thick branes
We consider chiral fermion confinement in scalar thick branes, which are
known to localize gravity, coupled through a Yukawa term. The conditions for
the confinement and their behavior in the thin-wall limit are found for various
different BPS branes, including double walls and branes interpolating between
different AdS_5 spacetimes. We show that only one massless chiral mode is
localized in all these walls, whenever the wall thickness is keep finite. We
also show that, independently of wall's thickness, chiral fermionic modes
cannot be localized in dS_4 walls embedded in a M_5 spacetime. Finally, massive
fermions in double wall spacetimes are also investigated. We find that, besides
the massless chiral mode localization, these double walls support
quasi-localized massive modes of both chiralities.Comment: 8 pages, 3 figure
Hypersymmetry bounds and three-dimensional higher-spin black holes
We investigate the hypersymmetry bounds on the higher spin black hole
parameters that follow from the asymptotic symmetry superalgebra in higher-spin
anti-de Sitter gravity in three spacetime dimensions. We consider anti-de
Sitter hypergravity for which the analysis is most transparent. This is a
Chern-Simons theory which contains,
besides a spin- field, a spin- field and a spin- field. The
asymptotic symmetry superalgebra is then the direct sum of two-copies of the
hypersymmetric extension of , which contains
fermionic generators of conformal weight and bosonic generators of
conformal weight in addition to the Virasoro generators. Following standard
methods, we derive bounds on the conserved charges from the anticommutator of
the hypersymmetry generators. The hypersymmetry bounds are nonlinear and are
saturated by the hypersymmetric black holes, which turn out to possess
-hypersymmetry and to be "extreme", where extremality can be defined in
terms of the entropy: extreme black holes are those that fulfill the
extremality bounds beyond which the entropy ceases to be a real function of the
black hole parameters. We also extend the analysis to other -solitonic
solutions which are maximally (hyper)symmetric.Comment: 26 page
Asymptotically locally flat spacetimes and dynamical black flowers in three dimensions
The theory of massive gravity proposed by Bergshoeff, Hohm and Townsend is
considered in the special case of the pure irreducibly fourth order quadratic
Lagrangian. It is shown that the asymptotically locally flat black holes of
this theory can be consistently deformed to "black flowers" that are no longer
spherically symmetric. Moreover, we construct radiating spacetimes settling
down to these black flowers in the far future. The generic case can be shown to
fit within a relaxed set of asymptotic conditions as compared to the ones of
general relativity at null infinity, while the asymptotic symmetries remain the
same. Conserved charges as surface integrals at null infinity are constructed
following a covariant approach, and their algebra represents BMS, but
without central extensions. For solutions possessing an event horizon, we
derive the first law of thermodynamics from these surface integrals.Comment: 14 pages, no figure
Microscopic entropy of the three-dimensional rotating black hole of BHT massive gravity
Asymptotically AdS rotating black holes for the Bergshoeff-Hohm-Townsend
(BHT) massive gravity theory in three dimensions are considered. In the special
case when the theory admits a unique maximally symmetric solution, apart from
the mass and the angular momentum, the black hole is described by an
independent "gravitational hair" parameter, which provides a negative lower
bound for the mass. This bound is saturated at the extremal case and, since the
temperature and the semiclassical entropy vanish, it is naturally regarded as
the ground state. The absence of a global charge associated with the
gravitational hair parameter reflects through the first law of thermodynamics
in the fact that the variation of this parameter can be consistently reabsorbed
by a shift of the global charges, giving further support to consider the
extremal case as the ground state. The rotating black hole fits within relaxed
asymptotic conditions as compared with the ones of Brown and Henneaux, such
that they are invariant under the standard asymptotic symmetries spanned by two
copies of the Virasoro generators, and the algebra of the conserved charges
acquires a central extension. Then it is shown that Strominger's holographic
computation for general relativity can also be extended to the BHT theory;
i.e., assuming that the quantum theory could be consistently described by a
dual conformal field theory at the boundary, the black hole entropy can be
microscopically computed from the asymptotic growth of the number of states
according to Cardy's formula, in exact agreement with the semiclassical result.Comment: 10 pages, no figure
Asymptotic structure of the Einstein-Maxwell theory on AdS
The asymptotic structure of AdS spacetimes in the context of General
Relativity coupled to the Maxwell field in three spacetime dimensions is
analyzed. Although the fall-off of the fields is relaxed with respect to that
of Brown and Henneaux, the variation of the canonical generators associated to
the asymptotic Killing vectors can be shown to be finite once required to span
the Lie derivative of the fields. The corresponding surface integrals then
acquire explicit contributions from the electromagnetic field, and become
well-defined provided they fulfill suitable integrability conditions, implying
that the leading terms of the asymptotic form of the electromagnetic field are
functionally related. Consequently, for a generic choice of boundary
conditions, the asymptotic symmetries are broken down to . Nonetheless, requiring compatibility
of the boundary conditions with one of the asymptotic Virasoro symmetries,
singles out the set to be characterized by an arbitrary function of a single
variable, whose precise form depends on the choice of the chiral copy.
Remarkably, requiring the asymptotic symmetries to contain the full conformal
group selects a very special set of boundary conditions that is labeled by a
unique constant parameter, so that the algebra of the canonical generators is
given by the direct sum of two copies of the Virasoro algebra with the standard
central extension and . This special set of boundary
conditions makes the energy spectrum of electrically charged rotating black
holes to be well-behaved.Comment: 18 pages, no figure
Higher Spin Black Holes with Soft Hair
We construct a new set of boundary conditions for higher spin gravity,
inspired by a recent "soft Heisenberg hair"-proposal for General Relativity on
three-dimensional Anti-de Sitter. The asymptotic symmetry algebra consists of a
set of affine current algebras. Its associated canonical charges
generate higher spin soft hair. We focus first on the spin-3 case and then
extend some of our main results to spin-, many of which resemble the spin-2
results: the generators of the asymptotic algebra naturally emerge from
composite operators of the charges through a twisted Sugawara
construction; our boundary conditions ensure regularity of the Euclidean
solutions space independently of the values of the charges; solutions, which we
call "higher spin black flowers", are stationary but not necessarily
spherically symmetric. Finally, we derive the entropy of higher spin black
flowers, and find that for the branch that is continuously connected to the BTZ
black hole, it depends only on the affine purely gravitational zero modes.
Using our map to -algebra currents we recover well-known expressions for
higher spin entropy. We also address higher spin black flowers in the metric
formalism and achieve full consistency with previous results.Comment: 24 pages, no figure
Remarks on the Myers-Perry and Einstein Gauss-Bonnet Rotating Solutions
The Kerr-type solutions of the five-dimensional Einstein and
Einstein-Gauss-Bonnet equations look pretty similar when written in Kerr-Schild
form. However the Myers-Perry spacetime is circular whereas the rotating
solution of the Einstein-Gauss-Bonnet theory is not. We explore some
consequences of this difference in particular regarding the (non) existence of
Boyer-Lindquist-type coordinates and the extension of the manifold
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