4,249 research outputs found
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
Neutrino Scattering in Heterogeneous Supernova Plasmas
Neutrinos in core collapse supernovae are likely trapped by neutrino-nucleus
elastic scattering. Using molecular dynamics simulations, we calculate neutrino
mean free paths and ion-ion correlation functions for heterogeneous plasmas.
Mean free paths are systematically shorter in plasmas containing a mixture of
ions compared to a plasma composed of a single ion species. This is because
neutrinos can scatter from concentration fluctuations. The dynamical response
function of a heterogeneous plasma is found to have an extra peak at low
energies describing the diffusion of concentration fluctuations. Our exact
molecular dynamics results for the static structure factor reduce to the Debye
Huckel approximation, but only in the limit of very low momentum transfers.Comment: 11 pages, 13 figure
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
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
Black Hole Entropy and Superconformal Field Theories on Brane-Antibrane Systems
We obtain the enropy of Schwarzschild and charged black holes in D>4 from
superconformal gases that live on p=10-D dimensional brane-antibrane systems
wrapped on T^p. The preperties of the strongly coupled superconformal theories
such as the appearance of hidden dimensions (for p=1,4) and fractional strings
(for p=5) are crucial for our results. In all cases, the Schwarzschild radius
is given by the transverse fluctuations of the branes and antibranes due to the
finite temperature. We show that our results can be generalized to multicharged
black holes.Comment: 24 pages in phyzzx.te
Bubbles Unbound: Bubbles of Nothing Without Kaluza-Klein
I present analytic time symmetric initial data for five dimensions describing
``bubbles of nothing'' which are asymptotically flat in the higher dimensional
sense, i.e. there is no Kaluza-Klein circle asymptotically. The mass and size
of these bubbles may be chosen arbitrarily and in particular the solutions
contain bubbles of any size which are arbitrarily light. This suggests the
solutions may be important phenomenologically and in particular I show that at
low energy there are bubbles which expand outwards, suggesting a new possible
instability in higher dimensions. Further, one may find bubbles of any size
where the only region of high curvature is confined to an arbitrarily small
volume.Comment: 27 pages, 2 figures, v2: minor changes, published versio
Statistical Effects and the Black Hole/D-brane Correspondence
The horizon area and curvature of three-charge BPS black strings are studied
in the D-brane ensemble for the stationary black string. The charge
distributions along the string are used to translate the classical expressions
for the horizon area and curvature of BPS black strings with waves into
operators on the D-brane Hilbert space. Despite the fact that any `wavy' black
string has smaller horizon area and divergent curvature, the typical values of
the horizon area and effects of the horizon curvature in the D-brane ensemble
deviate negligibly from those of the original stationary black string in the
limit of large integer charges. Whether this holds in general will depend on
certain properties of the quantum bound states.Comment: 13 pages, RevTex, small errors corrected, some interpretation changed
in light of new result
When Black Holes Meet Kaluza-Klein Bubbles
We explore the physical consequences of a recently discovered class of exact
solutions to five dimensional Kaluza-Klein theory. We find a number of
surprising features including: (1) In the presence of a Kaluza-Klein bubble,
there are arbitrarily large black holes with topology S^3. (2) In the presence
of a black hole or a black string, there are expanding bubbles (with de Sitter
geometry) which never reach null infinity. (3) A bubble can hold two black
holes of arbitrary size in static equilibrium. In particular, two large black
holes can be close together without merging to form a single black hole.Comment: 23 pages, 5 figures, v2: few comments on stability modifie
Towards a SDLCQ test of the Maldacena Conjecture
We consider the Maldacena conjecture applied to the near horizon geometry of
a D1-brane in the supergravity approximation and present numerical results of a
test of the conjecture against the boundary field theory calculation using
DLCQ. We previously calculated the two-point function of the stress-energy
tensor on the supergravity side; the methods of Gubser, Klebanov, Polyakov, and
Witten were used. On the field theory side, we derived an explicit expression
for the two-point function in terms of data that may be extracted from the
supersymmetric discrete light cone quantization (SDLCQ) calculation at a given
harmonic resolution. This yielded a well defined numerical algorithm for
computing the two-point function. For the supersymmetric Yang-Mills theory with
16 supercharges that arises in the Maldacena conjecture, the algorithm is
perfectly well defined; however, the size of the numerical computation
prevented us from obtaining a numerical check of the conjecture. We now present
numerical results with approximately 1000 times as many states as we previously
considered. These results support the Maldacena conjecture and are within
of the predicted numerical results in some regions. Our results are
still not sufficient to demonstrate convergence, and, therefore, cannot be
considered to a numerical proof of the conjecture. We present a method for
using a ``flavor'' symmetry to greatly reduce the size of the basis and discuss
a numerical method that we use which is particularly well suited for this type
of matrix element calculation.Comment: 10 pages, 1 figur
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