1,166 research outputs found
Factorization properties of genus-two bosonic and fermionic string partition functions
The genus-two bosonic and fermionic string partition functions factorize, in the separating pinching limit, into genus-one partition functions after integrating out the supermoduli with super-Beltrami support on the puncture points in the fermionic and heterotic case
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
Moduli Stabilization in Type IIB Orientifolds (I)
We discuss flux quantization and moduli stabilization in toroidal type IIB
Z_N - or Z_N x Z_M -orientifolds, focusing mainly on their orbifold limits.
After presenting a detailed discussion of their moduli spaces and effective
actions, we study the supersymmetric vacuum structure of these models and
derive criteria for the existence of stable minima. Furthermore, we briefly
investigate the models away from their orbifold points and comment on the
microscopic origin of their non-perturbative superpotentials.Comment: 97 pages + 2 figs, harvma
Thresholds for Intersecting D-branes Revisited
Gauge threshold corrections for intersecting D6-brane string models on
toroidal orbifold backgrounds are reconsidered. Both by dimensionally
regularising the appearing open string one-loop diagrams in tree-channel as
well as by zeta-function regularisation of the corresponding loop-channel
one-loop diagrams, we arrive at a result which takes into account the infrared
divergence from the contribution of the massless states in the running of the
gauge coupling constant as well as the contribution of states, which become
light in certain regions of the moduli space.Comment: 14 page
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
Flux compactification on smooth, compact three-dimensional toric varieties
Three-dimensional smooth, compact toric varieties (SCTV), when viewed as real
six-dimensional manifolds, can admit G-structures rendering them suitable for
internal manifolds in supersymmetric flux compactifications. We develop
techniques which allow us to systematically construct G-structures on SCTV and
read off their torsion classes. We illustrate our methods with explicit
examples, one of which consists of an infinite class of toric CP^1 bundles. We
give a self-contained review of the relevant concepts from toric geometry, in
particular the subject of the classification of SCTV in dimensions less or
equal to 3. Our results open up the possibility for a systematic construction
and study of supersymmetric flux vacua based on SCTV.Comment: 27 pages, 10 figures; v2: references, minor typos & improvement
Nonassociative Field Theory on Non-Geometric Spaces
We describe quasi-Hopf twist deformations of flat closed string
compactifications with non-geometric R-flux using a suitable cochain twist, and
construct nonassociative deformations of fields and differential calculus. We
report on our new findings in using this formalism to construct perturbative
nonassociative field theories on these backgrounds. We describe the
modifications to the usual classification of Feynman diagrams into planar and
non-planar graphs. The example of phi(4) theory is studied in detail and the
one-loop contributions to the two-point function are calculated.Comment: 6 pages; Contribution to the proceedings of the Workshop on
Noncommutative Field Theory and Gravity, Corfu, Greece, September 8-15, 201
N=1 effective potential from dual type-IIA D6/O6 orientifolds with general fluxes
We consider N=1 compactifications of the type-IIA theory on the T6/(Z2xZ2)
orbifold and O6 orientifold, in the presence of D6-branes and general NSNS, RR
and Scherk-Schwarz geometrical fluxes. Introducing a suitable dual formulation
of the theory, we derive and solve the Bianchi identities, and show how certain
combinations of fluxes can relax the constraints on D6-brane configurations
coming from the cancellation of RR tadpoles. We then compute, via generalized
dimensional reduction, the N=1, D=4 effective potential for the seven main
moduli, and comment on the relation with truncated N=4 gaugings. As a
byproduct, we obtain a general geometrical expression for the superpotential.
We finally identify a family of fluxes, compatible with all Bianchi identities,
that perturbatively stabilize all seven moduli in supersymmetric AdS4.Comment: 19 pages, no figures, JHEP3 LaTeX. Published versio
New supersymmetric AdS4 type II vacua
Building on our recent results on dynamic SU(3)xSU(3) structures we present a
set of sufficient conditions for supersymmetric AdS4xM6 backgrounds of type
IIA/IIB supergravity. These conditions ensure that the background solves,
besides the supersymmetry equations, all the equations of motion of type II
supergravity. The conditions state that the internal manifold is locally a
codimension-one foliation such that the five dimensional leaves admit a
Sasaki-Einstein structure. In type IIA the supersymmetry is N=2, and the total
six-dimensional internal space is locally an S^2 bundle over a four-dimensional
Kaehler-Einstein base; in IIB the internal space is the direct product of a
circle and a five-dimensional squashed Sasaki-Einstein manifold. Given any
five-dimensional Sasaki-Einstein manifold we construct the corresponding
families of type IIA/IIB vacua. The precise profiles of all the fields are
determined at the solution and depend on whether one is in IIA or in IIB. In
particular the background does not contain any sources, all fluxes (including
the Romans mass in IIA) are generally non-zero, and the dilaton and warp factor
are non-constant.Comment: 19 pages; clarifications added, version to appear in JHE
On supersymmetric Minkowski vacua in IIB orientifolds
Supersymmetric Minkowski vacua in IIB orientifold compactifications based on
orbifolds with background fluxes and non-perturbative superpotentials are
investigated. Especially, microscopic requirements and difficulties to obtain
such vacua are discussed. We show that orbifold models with one and two complex
structure moduli and supersymmetric 2-form flux can be successfully stabilized
to such vacua. By taking additional gaugino condensation on fixed space-time
filling D3-branes into account also models without complex structure can be
consistently stabilized to Minkowski vacua.Comment: 17 pages, 2 figures; More detailed proof for absence of complex flat
directions in susy AdS vacua given; Footnotes and reference adde
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