2,703 research outputs found
Small Black holes vs horizonless solutions in AdS
It is argued that the appropriate macroscopic description of half-BPS mesonic
chiral operators in generic toric gauge theories is in terms
of the geometric quantization of smooth horizonless configurations. The
relevance of different ensemble macroscopic descriptions is emphasized :
lorentzian vs euclidean configurations as (semiclassical) microstates vs saddle
points in an euclidean path integral.Comment: 10 pages; v2 improved entropy discussion and new references include
Supersymmetric Baryonic Branes
We derive an energy bound for a `baryonic' D5-brane probe in the background near the horizon of D3-branes. Configurations saturating
the bound are shown to be 1/4 supersymmetric -wrapped D5-branes, with a
total Born-Infeld charge . Previous results are recovered as a special case.
We derive a similar energy bound for a `baryonic' M5-brane probe in the
background of M5-branes. Configurations saturating the bound are again 1/4
supersymmetric and, in the near-horizon limit, provide a
worldvolume realization of the `baryon string' vertex of the
(2,0)-supersymmetric six-dimensional conformal field theory on coincident
M5-branes. For the full M5-background we find a worldvolume realization of the
Hanany-Witten effect in M-theory.Comment: 32 pp. Third version is the same as the second except for a little
additional material. To appear in JHE
Extremal black holes, Holography & Coarse graining
I review some of the concepts at the crossroads of gravitational
thermodynamics, holography and quantum mechanics. First, the origin of
gravitational thermodynamics due to coarse graining of quantum information is
exemplified using the half-BPS sector of SYM and its LLM
description in type IIB supergravity. The notion of black holes as effective
geometries, its relation to the fuzzball programme and some of the puzzles
raising for large black holes are discussed. Second, I review recent progress
for extremal black holes, both microscopically, discussing a constituent model
for stationary extremal non-bps black holes, and semiclassically, discussing
the extremal black hole/CFT conjecture. The latter is examined from the
AdS/CFT perspective. Third, I review the importance of the
holographic principle to encode non-local gravity features allowing us to
relate the gravitational physics of local observers with thermodynamics and the
role causality plays in these arguments by identifying horizons (screens) as
diathermic walls. I speculate with the emergence of an approximate CFT in the
deep IR close to any horizon and its relation with an effective dynamical
description of the degrees of freedom living on these holographic screens.Comment: 68 pages, 6 figures, invited review published in International
Journal of Modern Physics A; v2 contains further references and extra
comments on rotating extremal multi-center black hole configuration
Strings vs Spins on the Null Orbifold
We study the null orbifold singularity in 2+1 d flat space higher spin theory
as well as string theory. Using the Chern-Simons formulation of 2+1 d Einstein
gravity, we first observe that despite the singular nature of this geometry,
the eigenvalues of its Chern-Simons holonomy are trivial. Next, we construct a
resolution of the singularity in higher spin theory: a Kundt spacetime with
vanishing scalar curvature invariants. We also point out that the UV
divergences previously observed in the 2-to-2 tachyon tree level string
amplitude on the null orbifold do not arise in the
limit. We find all the divergences of the amplitude and demonstrate that the
ones remaining in the tensionless limit are physical IR-type divergences. We
conclude with a discussion on the meaning and limitations of higher spin
(cosmological) singularity resolution and its potential connection to string
theory.Comment: 27 pages, 5 figures, v2: comments about boundary conditions added,
strengthening the conclusio
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