69 research outputs found
Scalar Boundary Conditions in Lifshitz Spacetimes
We investigate the conditions imposable on a scalar field at the boundary of
the so- called Lifshitz spacetime which has been proposed as the dual to
Lifshitz field theories. For effective mass squared between -(d+z-1)^2/4 and
z^2-(d+z-1)^2/4, we find a one-parameter choice of boundary condition type. The
bottom end of this range corresponds to a Breitenlohner-Freedman bound; below
it, the Klein-Gordon operator need not be positive, so we cannot make sense of
the dynamics. Above the top end of the range, only one boundary condition type
is available; here we expect compact initial data will remain compact in the
future.Comment: references adde
Partition Functions in Even Dimensional AdS via Quasinormal Mode Methods
In this note, we calculate the one-loop determinant for a massive scalar
(with conformal dimension ) in even-dimensional AdS space,
using the quasinormal mode method developed in arXiv:0908.2657 by Denef,
Hartnoll, and Sachdev. Working first in two dimensions on the related Euclidean
hyperbolic plane , we find a series of zero modes for negative real values
of whose presence indicates a series of poles in the one-loop
partition function in the complex plane; these poles
contribute temperature-independent terms to the thermal AdS partition function
computed in arXiv:0908.2657. Our results match those in a series of papers by
Camporesi and Higuchi, as well as Gopakumar et.al. in arXiv:1103.3627 and
Banerjee et.al. in arXiv:1005.3044. We additionally examine the meaning of
these zero modes, finding that they Wick-rotate to quasinormal modes of the
AdS black hole. They are also interpretable as matrix elements of the
discrete series representations of in the space of smooth functions
on . We generalize our results to general even dimensional AdS,
again finding a series of zero modes which are related to discrete series
representations of , the motion group of .Comment: 27 pages; v2: minor updates and JHEP versio
Closed-String Tachyon Condensation and the Worldsheet Super-Higgs Effect
Alternative gauge choices for worldsheet supersymmetry can elucidate
dynamical phenomena obscured in the usual superconformal gauge. In the
particular example of the tachyonic heterotic string, we use a judicious
gauge choice to show that the process of closed-string tachyon condensation can
be understood in terms of a worldsheet super-Higgs effect. The worldsheet
gravitino assimilates the goldstino and becomes a dynamical propagating field.
Conformal, but not superconformal, invariance is maintained throughout.Comment: 4 pages; v2: typos corrected, a reference added; v3: final version,
to appear in Phys. Rev. Lett. (abstract and intro modified for a broader
audience
Boundary Causality vs Hyperbolicity for Spherical Black Holes in Gauss-Bonnet
We explore the constraints boundary causality places on the allowable
Gauss-Bonnet gravitational couplings in asymptotically AdS spaces, specifically
considering spherical black hole solutions. We additionally consider the
hyperbolicity properties of these solutions, positing that
hyperbolicity-violating solutions are sick solutions whose causality properties
provide no information about the theory they reside in. For both signs of the
Gauss-Bonnet coupling, spherical black holes violate boundary causality at
smaller absolute values of the coupling than planar black holes do. For
negative coupling, as we tune the Gauss-Bonnet coupling away from zero, both
spherical and planar black holes violate hyperbolicity before they violate
boundary causality. For positive coupling, the only hyperbolicity-respecting
spherical black holes which violate boundary causality do not do so appreciably
far from the planar bound. Consequently, eliminating hyperbolicity-violating
solutions means the bound on Gauss-Bonnet couplings from the boundary causality
of spherical black holes is no tighter than that from planar black holes.Comment: 17 pages, 6 figure
Hidden horizons in non-relativistic AdS/CFT
We study boundary Green's functions for spacetimes with non-relativistic
scaling symmetry. For this class of backgrounds, scalar modes with large
transverse momentum, or equivalently low frequency, have an exponentially
suppressed imprint on the boundary. We investigate the effect of these modes on
holographic two-point functions. We find that the boundary Green's function is
generically insensitive to horizon features on small transverse length scales.
We explicitly demonstrate this insensitivity for Lifshitz z=2, and then use the
WKB approximation to generalize our findings to Lifshitz z>1 and RG flows with
a Lifshitz-like region. We also comment on the analogous situation in
Schroedinger spacetimes. Finally, we exhibit the analytic properties of the
Green's function in these spacetimes.Comment: Abstract and Introduction updated, typos correcte
Towards Bulk Metric Reconstruction from Extremal Area Variations
The Ryu-Takayanagi and Hubeny-Rangamani-Takayanagi formulae suggest that bulk
geometry emerges from the entanglement structure of the boundary theory. Using
these formulae, we build on a result of Alexakis, Balehowsky, and Nachman to
show that in four bulk dimensions, the entanglement entropies of boundary
regions of disk topology uniquely fix the bulk metric in any region foliated by
the corresponding HRT surfaces. More generally, for a bulk of any dimension , knowledge of the (variations of the) areas of two-dimensional
boundary-anchored extremal surfaces of disk topology uniquely fixes the bulk
metric wherever these surfaces reach. This result is covariant and not reliant
on any symmetry assumptions; its applicability thus includes regions of strong
dynamical gravity such as the early-time interior of black holes formed from
collapse. While we only show uniqueness of the metric, the approach we present
provides a clear path towards an explicit spacetime metric reconstruction.Comment: 33+4 pages, 7 figures; v2: addressed referee comment
Universal features of Lifshitz Green's functions from holography
We examine the behavior of the retarded Green's function in theories with
Lifshitz scaling symmetry, both through dual gravitational models and a direct
field theory approach. In contrast with the case of a relativistic CFT, where
the Green's function is fixed (up to normalization) by symmetry, the generic
Lifshitz Green's function can a priori depend on an arbitrary function
, where is the
scale-invariant ratio of frequency to wavenumber, with dynamical exponent .
Nevertheless, we demonstrate that the imaginary part of the retarded Green's
function (i.e. the spectral function) of scalar operators is exponentially
suppressed in a window of frequencies near zero. This behavior is universal in
all Lifshitz theories without additional constraining symmetries. On the
gravity side, this result is robust against higher derivative corrections,
while on the field theory side we present two examples where the
exponential suppression arises from summing the perturbative expansion to
infinite order.Comment: 32 pages, 4 figures, v2: reference added, v3: fixed bug in
bibliograph
- …