54 research outputs found
Generalized Conformal Symmetry and Oblique AdS/CFT Correspondence for Matrix Theory
The large N behavior of Matrix theory is discussed on the basis of the
previously proposed generalized conformal symmetry. The concept of `oblique'
AdS/CFT correspondence, in which the conformal symmetry involves both the
space-time coordinates and the string coupling constant, is proposed. Based on
the explicit predictions for two-point correlators, possible implications for
the Matrix-theory conjecture are discussed.Comment: LaTeX, 10 pages, 2 figures, written version of the talk presented at
Strings'9
Fast Scramblers, Horizons and Expander Graphs
We propose that local quantum systems defined on expander graphs provide a
simple microscopic model for thermalization on quantum horizons. Such systems
are automatically fast scramblers and are motivated from the membrane paradigm
by a conformal transformation to the so-called optical metric.Comment: 22 pages, 2 figures. Added further discussion in section 3. Added
reference
Anisotropic scale invariant cosmology
We study a possibility of anisotropic scale invariant cosmology. It is shown
that within the conventional Einstein gravity, the violation of the null energy
condition is necessary. We construct an example based on a ghost condensation
model that violates the null energy condition. The cosmological solution
necessarily contains at least one contracting spatial direction as in the
Kasner solution. Our cosmology is conjectured to be dual to, if any, a
non-unitary anisotropic scale invariant Euclidean field theory. We investigate
simple correlation functions of the dual theory by using the holographic
computation. After compactification of the contracting direction, our setup may
yield a dual field theory description of the winding tachyon condensation that
might solve the singularity of big bang/crunch of the universe.Comment: 12 pages, v2: reference adde
Fast Scramblers Of Small Size
We investigate various geometrical aspects of the notion of `optical depth'
in the thermal atmosphere of black hole horizons. Optical depth has been
proposed as a measure of fast-crambling times in such black hole systems, and
the associated optical metric suggests that classical chaos plays a leading
role in the actual scrambling mechanism. We study the behavior of the optical
depth with the size of the system and find that AdS/CFT phase transitions with
topology change occur naturally as the scrambler becomes smaller than its
thermal length. In the context of detailed AdS/CFT models based on D-branes,
T-duality implies that small scramblers are described in terms of matrix
quantum mechanics.Comment: 14 pages, 3 figures. Added reference
Nonlocality vs. complementarity: a conservative approach to the information problem
A proposal for resolution of the information paradox is that "nice slice"
states, which have been viewed as providing a sharp argument for information
loss, do not in fact do so as they do not give a fully accurate description of
the quantum state of a black hole. This however leaves an information
*problem*, which is to provide a consistent description of how information
escapes when a black hole evaporates. While a rather extreme form of
nonlocality has been advocated in the form of complementarity, this paper
argues that is not necessary, and more modest nonlocality could solve the
information problem. One possible distinguishing characteristic of scenarios is
the information retention time. The question of whether such nonlocality
implies acausality, and particularly inconsistency, is briefly addressed. The
need for such nonlocality, and its apparent tension with our empirical
observations of local quantum field theory, may be a critical missing piece in
understanding the principles of quantum gravity.Comment: 11 pages of text and figures, + references. v2 minor text. v3 small
revisions to match final journal versio
No Forbidden Landscape in String/M-theory
Scale invariant but non-conformal field theories are forbidden in (1+1)
dimension, and so should be the corresponding holographic dual gravity
theories. We conjecture that such scale invariant but non-conformal field
configurations do not exist in the string/M-theory. We provide a proof of this
conjecture in the classical supergravity limit under a certain gauge condition.
Our proof does also apply in higher dimensional scale invariant but
non-conformal field configurations, which suggests that scale invariant but
non-conformal field theories may be forbidden in higher dimensions as well.Comment: 14 pages, v2: energy condition on c-theorem is corrected, v3: extra
assumption in the proof is discussed due to a sign error in the previous
versio
Brownian motion in AdS/CFT
We study Brownian motion and the associated Langevin equation in AdS/CFT. The
Brownian particle is realized in the bulk spacetime as a probe fundamental
string in an asymptotically AdS black hole background, stretching between the
AdS boundary and the horizon. The modes on the string are excited by the
thermal black hole environment and consequently the string endpoint at the
boundary undergoes an erratic motion, which is identified with an external
quark in the boundary CFT exhibiting Brownian motion. Semiclassically, the
modes on the string are thermally excited due to Hawking radiation, which
translates into the random force appearing in the boundary Langevin equation,
while the friction in the Langevin equation corresponds to the excitation on
the string being absorbed by the black hole. We give a bulk proof of the
fluctuation-dissipation theorem relating the random force and friction. This
work can be regarded as a step toward understanding the quantum microphysics
underlying the fluid-gravity correspondence. We also initiate a study of the
properties of the effective membrane or stretched horizon picture of black
holes using our bulk description of Brownian motion.Comment: 54 pages (38 pages + 5 appendices), 5 figures. v2: references added,
clarifications in 6.2. v3: clarifications, version submitted to JHE
Can the Horowitz-Maldacena proposal be an alternative to the firewall?
Recently, there have been discussions that black hole complementarity is
inconsistent and that the firewall is required to prohibit the observation of
duplicated information. It is thought that if the Horowitz-Maldacena proposal
works as a selection principle, then this may be an alternative to the
firewall. In this paper, we first point out that the Horowitz-Maldacena
proposal seems to help black hole complementarity for charged black holes.
However, if we consider the Hayden-Preskill argument further, which states that
a black hole can function as an information mirror after the information
retention time, then we can show that the Horowitz-Maldaceana proposal cannot
help black hole complementarity. This can be extended to neutral black hole
cases. Therefore, in conclusion, we find that dynamical black holes do not
respect complementarity, even with the Horowitz-Maldacena proposal.Comment: 11 pages, 3 figure
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
Condensation of an ideal gas with intermediate statistics on the horizon
We consider a boson gas on the stretched horizon of the Schwartzschild and
Kerr black holes. It is shown that the gas is in a Bose-Einstein condensed
state with the Hawking temperature if the particle number of the
system be equal to the number of quantum bits of space-time N \simeq
{A}/{{\l_{p}}^{2}}. Entropy of the gas is proportional to the area of the
horizon by construction. For a more realistic model of quantum degrees of
freedom on the horizon, we should presumably consider interacting bosons
(gravitons). An ideal gas with intermediate statistics could be considered as
an effective theory for interacting bosons. This analysis shows that we may
obtain a correct entropy just by a suitable choice of parameter in the
intermediate statistics.Comment: 12 pages, added new sections related to an ideal gas with
intermediate statistic
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