332 research outputs found
Classical Limit of Black Hole Quantum N-Portrait and BMS Symmetry
Black hole entropy, denoted by N, in (semi)classical limit is infinite. This
scaling reveals a very important information about the qubit degrees of freedom
that carry black hole entropy. Namely, the multiplicity of qubits scales as N,
whereas their energy gap and their coupling as 1/N. Such a behavior is indeed
exhibited by Bogoliubov-Goldstone degrees of freedom of a quantum-critical
state of N soft gravitons (a condensate or a coherent state) describing the
black hole quantum portrait. They can be viewed as the Goldstone modes of a
broken symmetry acting on the graviton condensate. In this picture Minkowski
space naturally emerges as a coherent state of infinite-N gravitons of infinite
wavelength and it carries an infinite entropy. In this paper we ask what is the
geometric meaning (if any) of the classical limit of this symmetry. We argue
that the infinite-N limit of Bogoliubov-Goldstone modes of critical graviton
condensate is described by recently-discussed classical BMS super-translations
broken by the black hole geometry. However, the full black hole information can
only be recovered for finite N, since the recovery time becomes infinite in
classical limit in which N is infinite.Comment: 15 pages, Late
A Class of N=1 Dual String Pairs and its Modular Superpotential
We compare the N=1 F-theory compactification of Donagi, Grassi and Witten
with modular superpotential - and some closely related models - to dual
heterotic models. We read of the F-theory spectrum from the cohomology of the
fourfold and discuss on the heterotic side the gauge bundle moduli sector
(including the spectral surface) and the necessary fivebranes. Then we consider
the N=1 superpotential and show how a heterotic superpotential matching the
F-theory computation is built up by worldsheet instantons. Finally we discuss
how the original modular superpotential should be corrected by an additional
modular correction factor, which on the F-theory side matches nicely with a
`curve counting function' for the del Pezzo surface. On the heterotic side we
derive the same factor demanding correct T-duality transformation properties of
the superpotential.Comment: 18 pages, Late
Non-commutative D- and M-brane Bound States
We analyze certain brane bound states in M-theory and their descendants in type IIA string theory, all involving 3-form or 2-form background fluxes. Among them are configurations which represent NCYM, NCOS and ODp-theories in the scaling limit of OM-theory. In particular, we show how the conditions for the embedding to preserve supersymmetry are modified by the presence of the flux and discuss their relations for the various different bound states. Via the formalism of geometric quantization such a deformation of a supersymmetric cycle is related to a non-commutativity of its coordinates. We also study possible non-commutative deformations of the Seiberg-Witten curve of N=2 supersymmetric gauge theories due to non-trivial H-flux
Superconformal N=1 Gauge Theories, beta-Function Invariants and their Behavior under Seiberg Duality
In this paper we discuss some aspects of the behavior of superconformal N=1
models under Seiberg's duality. Our claim is that if an electric gauge theory
is superconformal on some marginal subspace of all coupling constants then its
magnetic dual must be also superconformal on a corresponding moduli space of
dual couplings. However this does not imply that the magnetic dual of a
completely finite N=1 gauge theory is again finite. Moreover we generalize this
statement conjecturing that also for non-superconformal N=1 models the
determinant of the beta-function equations is invariant under Seiberg duality.
During the course of this investigation we construct some superconformal N=1
gauge theories which were not yet discussed before.Comment: 14 pages, revised version contains two changes in citatio
Non-perturbative Yukawa Couplings from String Instantons
Non-perturbative D-brane instantons can generate perturbatively absent though
phenomenologically relevant couplings for Type II orientifold compactifications
with D-branes. We discuss the generation of the perturbatively vanishing SU(5)
GUT Yukawa coupling of type 10 10 5_H. Moreover, for a simple globally
consistent intersecting D6-brane model, we discuss the generation of mass terms
for matter fields. This can serve as a mechanism for decoupling exotic matter.Comment: 4 pages, 2 tables, 2 figure
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