2,792 research outputs found
Probing black holes in non-perturbative gauge theory
We use a 0-brane to probe a ten-dimensional near-extremal black hole with N
units of 0-brane charge. We work directly in the dual strongly-coupled quantum
mechanics, using mean-field methods to describe the black hole background
non-perturbatively. We obtain the distribution of W boson masses, and find a
clear separation between light and heavy degrees of freedom. To localize the
probe we introduce a resolving time and integrate out the heavy modes. After a
non-trivial change of coordinates, the effective potential for the probe agrees
with supergravity expectations. We compute the entropy of the probe, and find
that the stretched horizon of the black hole arises dynamically in the quantum
mechanics, as thermal restoration of unbroken U(N+1) gauge symmetry. Our
analysis of the quantum mechanics predicts a correct relation between the
horizon radius and entropy of a black hole.Comment: 30 pages, LaTeX, 8 eps figures. v2: references added. v3: more
reference
Dynamical tachyons on fuzzy spheres
We study the spectrum of off-diagonal fluctuations between displaced fuzzy
spheres in the BMN plane wave matrix model. The displacement is along the plane
of the fuzzy spheres. We find that when two fuzzy spheres intersect at angles
classical tachyons develop and that the spectrum of these modes can be computed
analytically. These tachyons can be related to the familiar Nielsen-Olesen
instabilities in Yang-Mills theory on a constant magnetic background. Many
features of the problem become more apparent when we compare with maximally
supersymmetric Yang-Mills on a sphere, of which this system is a truncation. We
also set up a simple oscillatory trajectory on the displacement between the
fuzzy spheres and study the dynamics of the modes as they become tachyonic for
part of the oscillations. We speculate on their role regarding the possible
thermalization of the system.Comment: 34 pages, 4 figures; v2: 35 pages, expanded sec. 4.3, added
reference
Holographic representation of local bulk operators
The Lorentzian AdS/CFT correspondence implies a map between local operators
in supergravity and non-local operators in the CFT. By explicit computation we
construct CFT operators which are dual to local bulk fields in the
semiclassical limit. The computation is done for general dimension in global,
Poincare and Rindler coordinates. We find that the CFT operators can be taken
to have compact support in a region of the complexified boundary whose size is
set by the bulk radial position. We show that at finite N the number of
independent commuting operators localized within a bulk volume saturates the
holographic bound.Comment: 36 pages, LaTeX, 4 eps figure
A Comment on Zero-brane Quantum Mechanics
We consider low energy, non-relativistic scattering of two Dirichlet
zero-branes as an exercise in quantum mechanics. For weak string coupling and
sufficiently small velocity, the dynamics is governed by an effective U(2)
gauge theory in 0+1 dimensions. At low energies, D-brane scattering can
reliably probe distances much shorter than the string scale. The only length
scale in the quantum mechanics problem is the eleven dimensional Planck length.
This provides evidence for the role of scales shorter than the string length in
the weakly coupled dynamics of type IIA strings.Comment: 9 pages, harvmac, improved treatment of 2+1 proble
Constructing local bulk observables in interacting AdS/CFT
Local operators in the bulk of AdS can be represented as smeared operators in
the dual CFT. We show how to construct these bulk observables by requiring that
the bulk operators commute at spacelike separation. This extends our previous
work by taking interactions into account. Large-N factorization plays a key
role in the construction. We show diagrammatically how this procedure is
related to bulk Feynman diagrams.Comment: 41 pages, LaTeX. v2: reference correcte
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