258 research outputs found
Dynamics of First Order Transitions with Gravity Duals
A first order phase transition usually proceeds by nucleating bubbles of the
new phase which then rapidly expand. In confining gauge theories with a gravity
dual, the deconfined phase is often described by a black hole. If one starts in
this phase and lowers the temperature, the usual description of how the phase
transition proceeds violates the area theorem. We study the dynamics of this
phase transition using the insights from the dual gravitational description,
and resolve this apparent contradiction.Comment: 11 pages, 1 figure. v2: minor clarifications, reference adde
Comments on Black Holes in String Theory
A very brief review is given of some of the developments leading to our
current understanding of black holes in string theory. This is followed by a
discussion of two possible misconceptions in this subject - one involving the
stability of small black holes and the other involving scale radius duality.
Finally, I describe some recent results concerning quasinormal modes of black
holes in anti de Sitter spacetime, and their implications for strongly coupled
conformal field theories (in various dimensions).Comment: 13 pages. Talk given at Strings '99, Potsdam, German
Tachyon Condensation and Black Strings
We show that under certain conditions, closed string tachyon condensation
produces a topology changing transition from black strings to Kaluza-Klein
"bubbles of nothing." This can occur when the curvature at the horizon is much
smaller than the string scale, so the black string is far from the
correspondence point when it would make a transition to an excited fundamental
string. This provides a dramatic new endpoint to Hawking evaporation. A similar
transition occurs for black p-branes, and can be viewed as a nonextremal
version of a geometric transition. Applications to AdS black holes and the AdS
soliton are also discussed.Comment: 23 pages, 1 figure, v2: references adde
Comments on Black Holes in Matrix Theory
The recent suggestion that the entropy of Schwarzschild black holes can be
computed in matrix theory using near-extremal D-brane thermodynamics is
examined. It is found that the regime in which this approach is valid actually
describes black strings stretched across the longitudinal direction, near the
transition where black strings become unstable to the formation of black holes.
It is argued that the appropriate dynamics on the other (black hole) side of
the transition is that of the zero modes of the corresponding super Yang-Mills
theory. A suggestive mean field theory argument is given for the entropy of
black holes in all dimensions. Consequences of the analysis for matrix theory
and the holographic principle are discussed.Comment: 15 pages, harvmac, minor errors correcte
Quantum Probes of Spacetime Singularities
It is shown that there are static spacetimes with timelike curvature
singularities which appear completely nonsingular when probed with quantum test
particles. Examples include extreme dilatonic black holes and the fundamental
string solution. In these spacetimes, the dynamics of quantum particles is well
defined and uniquely determined.Comment: 12 pages, RevTeX, no figures, A few breif comments added and typos
correcte
Negative Energy, Superluminosity and Holography
The holographic connection between large Super Yang Mills theory and
gravity in anti deSitter space requires unfamiliar behavior of the SYM theory
in the limit that the curvature of the AdS geometry becomes small. The
paradoxical behavior includes superluminal oscillations and negative energy
density. These effects typically occur in the SYM description of events which
take place far from the boundary of AdS when the signal from the event arrives
at the boundary. The paradoxes can be resolved by assuming a very rich
collection of hidden degrees of freedom of the SYM theory which store
information but give rise to no local energy density. These degrees of freedom,
called precursors, are needed to make possible sudden apparently acausal energy
momentum flows. Such behavior would be impossible in classical field theory as
a consequence of the positivity of the energy density. However we show that
these effects are not only allowed in quantum field theory but that we can
model them in free quantum field theory.Comment: Expanded version replacing earlier hep-th/990218
New stability results for Einstein scalar gravity
We consider asymptotically anti de Sitter gravity coupled to a scalar field
with mass slightly above the Breitenlohner-Freedman bound. This theory admits a
large class of consistent boundary conditions characterized by an arbitrary
function . An important open question is to determine which admit stable
ground states. It has previously been shown that the total energy is bounded
from below if is bounded from below and the bulk scalar potential
admits a suitable superpotential. We extend this result and show that the
energy remains bounded even in some cases where can become arbitrarily
negative. As one application, this leads to the possibility that in
gauge/gravity duality, one can add a double trace operator with negative
coefficient to the dual field theory and still have a stable vacuum
The Value of Singularities
We point out that spacetime singularities play a useful role in gravitational
theories by eliminating unphysical solutions. In particular, we argue that any
modification of general relativity which is completely nonsingular cannot have
a stable ground state. This argument applies both to classical extensions of
general relativity, and to candidate quantum theories of gravity.Comment: 5 pages, no figures; a few clarifying comments adde
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