862 research outputs found
Strings on conifolds from strong coupling dynamics: quantitative results
Three quantitative features of string theory on AdS_5 x X_5, for any
(quasi)regular Sasaki-Einstein X_5, are recovered exactly from an expansion of
field theory at strong coupling around configurations in the moduli space of
vacua. These configurations can be thought of as a generalized matrix model of
(local) commuting matrices. First, we reproduce the spectrum of scalar
Kaluza-Klein modes on X_5. Secondly, we recover the precise spectrum of BMN
string states, including a nontrivial dependence on the volume of X_5. Finally,
we show how the radial direction in global AdS_5 emerges universally in these
theories by exhibiting states dual to AdS giant gravitons.Comment: 1+28 pages. 1 figur
Black Hole Production from High Energy Scattering in AdS/CFT
In this article we show how to set up initial states in SYM
theory that correspond to high energy graviton collisions, leading to black
hole formation in . For this purpose, we study states in the
gauge theory that are dual to graviton wavepackets localized at the center of
, and carrying large angular momentum along the . These states are
created by exciting only the s-wave mode of one of the complex adjoint scalars
of SYM. For a single graviton, the state is 1/2 BPS and one can show that it is
dual to a linearized 1/2 BPS geometry in the bulk. Exploiting this dictionary,
we show how to localize the particle's wavefunciton so that the dual linearized
metric has the form of a Aichelburg-Sexl shock wave. One can then put two such
shock waves into a head-on collision, which is known to produce a trapped
surface. Finally, we discuss the prospect of studying graviton scattering
directly at strong coupling in the gauge theory using a reduced model of matrix
quantum mechanics.Comment: 11 pages, revtex format, no figure
Strings on conifolds from strong coupling dynamics, part I
A method to solve various aspects of the strong coupling expansion of the
superconformal field theory duals of AdS_5 x X geometries from first principles
is proposed. The main idea is that at strong coupling the configurations that
dominate the low energy dynamics of the field theory compactified on a three
sphere are given by certain non-trivial semi-classical configurations in the
moduli space of vacua.
We show that this approach is self-consistent and permits one to express most
of the dynamics in terms of an effective N=4 SYM dynamics. This has the
advantage that some degrees of freedom that move the configurations away from
moduli space can be treated perturbatively, unifying the essential low energy
dynamics of all of these theories. We show that with this formalism one can
compute the energies of strings in the BMN limit in the Klebanov-Witten theory
from field theory considerations, matching the functional form of results found
using AdS geometry. This paper also presents various other technical results
for the semiclassical treatment of superconformal field theories.Comment: 52 pages, JHEP3 styl
A study of open strings ending on giant gravitons, spin chains and integrability
We systematically study the spectrum of open strings attached to half BPS
giant gravitons in the N=4 SYM AdS/CFT setup. We find that some null
trajectories along the giant graviton are actually null geodesics of AdS_5x
S^5, so that we can study the problem in a plane wave limit setup. We also find
the description of these states at weak 't Hooft coupling in the dual CFT. We
show how the dual description is given by an open spin chain with variable
number of sites. We analyze this system in detail and find numerical evidence
for integrability. We also discover an interesting instability of long open
strings in Ramond-Ramond backgrounds that is characterized by having a
continuum spectrum of the string, which is separated from the ground state by a
gap. This instability arises from accelerating the D-brane on which the strings
end via the Ramond-Ramond field. From the integrable spin chain point of view,
this instability prevents us from formulating the integrable structure in terms
of a Bethe Ansatz construction.Comment: 38 pages+appendices, 9 figures. Uses JHEP3. v2: added reference
Multi-matrix models and emergent geometry
Encouraged by the AdS/CFT correspondence, we study emergent local geometry in
large N multi-matrix models from the perspective of a strong coupling
expansion. By considering various solvable interacting models we show how the
emergence or non-emergence of local geometry at strong coupling is captured by
observables that effectively measure the mass of off-diagonal excitations about
a semiclassical eigenvalue background. We find emergent geometry at strong
coupling in models where a mass term regulates an infrared divergence. We also
show that our notion of emergent geometry can be usefully applied to fuzzy
spheres. Although most of our results are analytic, we have found numerical
input valuable in guiding and checking our results.Comment: 1+34 pages, 4 figures. References adde
Aspects of ABJM orbifolds with discrete torsion
We analyze orbifolds with discrete torsion of the ABJM theory by a finite
subgroup of . Discrete torsion is implemented by
twisting the crossed product algebra resulting after orbifolding. It is shown
that, in general, the order of the cocycle we chose to twist the algebra by
enters in a non trivial way in the moduli space. To be precise, the M-theory
fiber is multiplied by a factor of in addition to the other effects that
were found before in the literature. Therefore we got a
action on the fiber. We present a general
analysis on how this quotient arises along with a detailed analysis of the
cases where is abelian
A Monte-Carlo study of the AdS/CFT correspondence: an exploration of quantum gravity effects
In this paper we study the AdS/CFT correspondence for N=4 SYM with gauge
group U(N), compactified on S^3 in four dimensions using Monte-Carlo
techniques. The simulation is based on a particular reduction of degrees of
freedom to commuting matrices of constant fields, and in particular, we can
write the wave functions of these degrees of freedom exactly. The square of the
wave function is equivalent to a probability density for a Boltzman gas of
interacting particles in six dimensions. From the simulation we can extract the
density particle distribution for each wave function, and this distribution can
be interpreted as a special geometric locus in the gravitational dual. Studying
the wave functions associated to half-BPS giant gravitons, we are able to show
that the matrix model can measure the Planck scale directly. We also show that
the output of our simulation seems to match various theoretical expectations in
the large N limit and that it captures 1/N effects as statistical fluctuations
of the Boltzman gas with the expected scaling. Our results suggest that this is
a very promising approach to explore quantum corrections and effects in
gravitational physics on AdS spaces.Comment: 40 pages, 7 figures, uses JHEP. v2: references adde
BPS Condensates, Matrix Models and Emergent String Theory
A prescription is given for computing anomalous dimensions of single trace
operators in SYM at strong coupling and large using a reduced model of
matrix quantum mechanics. The method involves treating some parts of the
operators as "BPS condensates" which, in certain limit, have a dual description
as null geodesics on the . In the gauge theory, the condensate is similar
to a representative of the chiral ring and it is described by a background of
commuting matrices. Excitations around these condensates correspond to
excitations around this background and take the form of "string bits" which are
dual to the "giant magnons" of Hofman and Maldacena. In fact, the matrix model
approach gives a {\it quantum} description of these string configurations and
explains why the infinite momentum limit suppresses the quantum effects. This
method allows, not only to derive part of the classical sigma model Hamiltonian
of the dual string (in the infinite momentum limit), but also its quantum
canonical structure. Therefore, it provides an alternative method of testing
the AdS/CFT correspondence without the need of integrability.Comment: 36 pages, 1 figure, 2 appendices, v2: references adde
A renormalization procedure for tensor models and scalar-tensor theories of gravity
Tensor models are more-index generalizations of the so-called matrix models,
and provide models of quantum gravity with the idea that spaces and general
relativity are emergent phenomena. In this paper, a renormalization procedure
for the tensor models whose dynamical variable is a totally symmetric real
three-tensor is discussed. It is proven that configurations with certain
Gaussian forms are the attractors of the three-tensor under the renormalization
procedure. Since these Gaussian configurations are parameterized by a scalar
and a symmetric two-tensor, it is argued that, in general situations, the
infrared dynamics of the tensor models should be described by scalar-tensor
theories of gravity.Comment: 20 pages, 3 figures, references added, minor correction
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