1,344 research outputs found
Left-Right Entanglement Entropy of Dp-branes
We compute the left-right entanglement entropy for Dp-branes in string
theory. We employ the CFT approach to string theory Dp-branes, in particular,
its presentation as coherent states of the closed string sector. The
entanglement entropy is computed as the von Neumann entropy for a density
matrix resulting from integration over the left-moving degrees of freedom. We
discuss various crucial ambiguities related to sums over spin structures and
argue that different choices capture different physics; however, we advance a
themodynamic argument that seems to favor a particular choice of replica. We
also consider Dp branes on compact dimensions and verify that the effects of
T-duality act covariantly on the Dp brane entanglement entropy. We find that
generically the left-right entanglement entropy provides a suitable
generalization of boundary entropy and of the D-brane tension.Comment: 20 pages, 3 figures. v2: A thermodynamic argument favoring a
particular treatment of spin structures is advanced; one figure improved and
references adde
Gravitational Collapse, Chaos in CFT Correlators and the Information Paradox
We consider gravitational collapse of a massless scalar field in
asymptotically Anti de Sitter spacetime. Following the AdS/CFT dictionary we
further study correlations in the field theory side by way of the Klein-Gordon
equation of a probe scalar field in the collapsing background. We present
evidence that in a certain regime the probe scalar field behaves chaotically,
thus supporting Hawking's argument in the black hole information paradox
proposing that although the information can be retrieved in principle,
deterministic chaos impairs, in practice, the process of unitary extraction of
information from a black hole. We emphasize that quantum chaos will change this
picture.Comment: 5 pages, 3 figure
Left-Right Entanglement Entropy of Boundary States
We study entanglement entropy of boundary states in a free bosonic conformal
field theory. A boundary state can be thought of as composed of a particular
combination of left and right-moving modes of the two-dimensional conformal
field theory. We investigate the reduced density matrix obtained by tracing
over the right-moving modes in various boundary states. We consider Dirichlet
and Neumann boundary states of a free noncompact as well as a compact boson.
The results for the entanglement entropy indicate that the reduced system can
be viewed as a thermal CFT gas. Our findings are in agreement and generalize
results in quantum mechanics and quantum field theory where coherent states can
also be considered. In the compact case we verify that the entanglement entropy
expressions are consistent with T-duality.Comment: 15 pages, no figures. v2 References added, typos fixe
On Exactly Marginal Deformations Dual to -Field Moduli of IIB Theory on SE
The complex dimension of the space of exactly marginal deformations for
quiver CFTs dual to IIB theory compactified on is known to be
generically three. Simple general formulas already exist for two of the exactly
marginal directions in the space of couplings, one of which corresponds to the
sum of the (inverse squared of) gauge couplings, and the other to the
-deformation. Here we identify the third exactly marginal direction,
which is dual to the modulus on the gravity side. This
identification leads to a relation between the field theory gauge couplings and
the vacuum expectation value of the gravity modulus that we further support by
a computation related to the chiral anomaly induced by added fractional branes.
We also present a simple algorithm for finding similar exactly marginal
directions in any CFT described by brane tiling, and demonstrate it for the
quiver CFTs dual to IIB theory compactified on and the Suspended
Pinch Point.Comment: 28 pages, JHEP style. v2: minor corrections, added references and
acknowledgements. v3: a number of speculative comments regarding the
application of the Konishi anomaly equation to our problem are removed. v4:
the proposal in Eq. (2.4) added back as a conjectur
Chaos Rules out Integrability of Strings in AdS_5 x T^{1,1}
We show that certain classical string configurations in AdS_5 x T^{1,1} are
chaotic. This answers the question of integrability of string on such
backgrounds in the negative. We consider a string localized in the center of
AdS_5 that winds around two circles of T^{1,1}. The corresponding dynamical
system is equivalent to two coupled gravitational pendula and allows a very
intuitive understanding. We find conclusive evidence of chaotic behavior by
systematically analyzing the workings of the KAM theorem. We also show that the
largest Lyapunov exponent is positive.Comment: 12 pages, 11 figure
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