429 research outputs found
Radiation from the non-extremal fuzzball
The fuzzball proposal says that the information of the black hole state is
distributed throughout the interior of the horizon in a `quantum fuzz'. There
are special microstates where in the dual CFT we have `many excitations in the
same state'; these are described by regular classical geometries without
horizons. Jejjala et.al constructed non-extremal regular geometries of this
type. Cardoso et. al then found that these geometries had a classical
instability. In this paper we show that the energy radiated through the
unstable modes is exactly the Hawking radiation for these microstates. We do
this by (i) starting with the semiclassical Hawking radiation rate (ii) using
it to find the emission vertex in the CFT (iii) replacing the Boltzman
distributions of the generic CFT state with the ones describing the microstate
of interest (iv) observing that the emission now reproduces the classical
instability. Because the CFT has `many excitations in the same state' we get
the physics of a Bose-Einstein condensate rather than a thermal gas, and the
usually slow Hawking emission increases, by Bose enhancement, to a classically
radiated field. This system therefore provides a complete gravity description
of information-carrying radiation from a special microstate of the nonextremal
hole.Comment: corrected typo
Star product and the general Leigh-Strassler deformation
We extend the definition of the star product introduced by Lunin and
Maldacena to study marginal deformations of N=4 SYM. The essential difference
from the latter is that instead of considering U(1)xU(1) non-R-symmetry, with
charges in a corresponding diagonal matrix, we consider two Z_3-symmetries
followed by an SU(3) transformation, with resulting off-diagonal elements. From
this procedure we obtain a more general Leigh-Strassler deformation, including
cubic terms with the same index, for specific values of the coupling constants.
We argue that the conformal property of N=4 SYM is preserved, in both beta-
(one-parameter) and gamma_{i}-deformed (three-parameters) theories, since the
deformation for each amplitude can be extracted in a prefactor. We also
conclude that the obtained amplitudes should follow the iterative structure of
MHV amplitudes found by Bern, Dixon and Smirnov.Comment: 21 pages, no figures, JHEP3, v2: references added, v3: appendix A
added, v4: clarification in section 3.
Comments on black holes I: The possibility of complementarity
We comment on a recent paper of Almheiri, Marolf, Polchinski and Sully who
argue against black hole complementarity based on the claim that an infalling
observer 'burns' as he approaches the horizon. We show that in fact
measurements made by an infalling observer outside the horizon are
statistically identical for the cases of vacuum at the horizon and radiation
emerging from a stretched horizon. This forces us to follow the dynamics all
the way to the horizon, where we need to know the details of Planck scale
physics. We note that in string theory the fuzzball structure of microstates
does not give any place to 'continue through' this Planck regime. AMPS argue
that interactions near the horizon preclude traditional complementarity. But
the conjecture of 'fuzzball complementarity' works in the opposite way: the
infalling quantum is absorbed by the fuzzball surface, and it is the resulting
dynamics that is conjectured to admit a complementary description.Comment: 34 pages, 6 figures, v3: clarifications & references adde
One-loop divergences in the two-dimensional non-anticommutative supersymmetric sigma-model
We discuss the structure of the non-anticommutative N=2 non-linear
sigma-model in two dimensions, constructing differential operators which
implement the deformed supersymmetry generators and using them to reproduce the
classical action. We then compute the one-loop quantum corrections and express
them in a more compact form using the differential operators.Comment: 20pp, 8 figures, uses LaTeX. Title expanded to clarify conten
The information paradox: A pedagogical introduction
The black hole information paradox is a very poorly understood problem. It is
often believed that Hawking's argument is not precisely formulated, and a more
careful accounting of naturally occurring quantum corrections will allow the
radiation process to become unitary. We show that such is not the case, by
proving that small corrections to the leading order Hawking computation cannot
remove the entanglement between the radiation and the hole. We formulate
Hawking's argument as a `theorem': assuming `traditional' physics at the
horizon and usual assumptions of locality we will be forced into mixed states
or remnants. We also argue that one cannot explain away the problem by invoking
AdS/CFT duality. We conclude with recent results on the quantum physics of
black holes which show the the interior of black holes have a `fuzzball'
structure. This nontrivial structure of microstates resolves the information
paradox, and gives a qualitative picture of how classical intuition can break
down in black hole physics.Comment: 38 pages, 7 figures, Latex (Expanded form of lectures given at CERN
for the RTN Winter School, Feb 09), typo correcte
Spacetime in String Theory
We give a brief overview of the nature of spacetime emerging from string
theory. This is radically different from the familiar spacetime of Einstein's
relativity. At a perturbative level, the spacetime metric appears as ``coupling
constants" in a two dimensional quantum field theory. Nonperturbatively (with
certain boundary conditions), spacetime is not fundamental but must be
reconstructed from a holographic, dual theory.Comment: 20 pages; references adde
The Scherk-Schwarz mechanism as a flux compactification with internal torsion
The aim of this paper is to make progress in the understanding of the
Scherk-Schwarz dimensional reduction in terms of a compactification in the
presence of background fluxes and torsion. From the eleven dimensional
supergravity point of view, we find that a general E6(6) S-S phase may be
obtained by turning on an appropriate background torsion, together with
suitable fluxes, some of which can be directly identified with certain
components of the four-form field-strength. Furthermore, we introduce a novel
(four dimensional) approach to the study of dualities between flux/torsion
compactifications of Type II/M-theory. This approach defines the action that
duality should have on the background quantities, in order for the E7(7)
invariance of the field equations and Bianchi identities to be restored also in
the presence of fluxes/torsion. This analysis further implies the
interpretation of the torsion flux as the T-dual of the NS three-form flux.Comment: Version published on J. High Energy Phy
Vortex loop operators, M2-branes and holography
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Membrane paradigm realized?
Are there any degrees of freedom on the black hole horizon? Using the
`membrane paradigm' we can reproduce coarse-grained physics outside the hole by
assuming a fictitious membrane just outside the horizon. But to solve the
information puzzle we need `real' degrees of freedom at the horizon, which can
modify Hawking's evolution of quantum modes. We argue that recent results on
gravitational microstates imply a set of real degrees of freedom just outside
the horizon; the state of the hole is a linear combination of rapidly
oscillating gravitational solutions with support concentrated just outside the
horizon radius. The collective behavior of these microstate solutions may give
a realization of the membrane paradigm, with the fictitious membrane now
replaced by real, explicit degrees of freedom.Comment: 8 pages, Latex, 3 figures (Essay given second place in Gravity
Research Foundation essay competition 2010
The general (2,2) gauged sigma model with three--form flux
We find the conditions under which a Riemannian manifold equipped with a
closed three-form and a vector field define an on--shell N=(2,2) supersymmetric
gauged sigma model. The conditions are that the manifold admits a twisted
generalized Kaehler structure, that the vector field preserves this structure,
and that a so--called generalized moment map exists for it. By a theorem in
generalized complex geometry, these conditions imply that the quotient is again
a twisted generalized Kaehler manifold; this is in perfect agreement with
expectations from the renormalization group flow. This method can produce new
N=(2,2) models with NS flux, extending the usual Kaehler quotient construction
based on Kaehler gauged sigma models.Comment: 24 pages. v2: typos fixed, other minor correction
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