17,992 research outputs found
Wall Crossing and M-theory
We study BPS bound states of D0 and D2 branes on a single D6 brane wrapping a
Calabi-Yau 3-fold X. When X has no compact 4-cyles, the BPS bound states are
organized into a free field Fock space, whose generators correspond to BPS
states of spinning M2 branes in M-theory compactified down to 5 dimensions by a
Calabi-Yau 3-fold X. The generating function of the D-brane bound states is
expressed as a reduction of the square of the topological string partition
function, in all chambers of the Kahler moduli space.Comment: 19 pages, 1 figur
Tunneling-driven breakdown of the 331 state and the emergent Pfaffian and composite Fermi liquid phases
We examine the possibility of creating the Moore-Read Pfaffian in the lowest
Landau level when the multicomponent Halperin 331 state (believed to describe
quantum Hall bilayers and wide quantum wells at the filling factor )
is destroyed by the increase of tunneling. Using exact diagonalization of the
bilayer Hamiltonian with short-range and long-range (Coulomb) interactions in
spherical and periodic rectangular geometries, we establish that tunneling is a
perturbation that drives the 331 state into a compressible composite Fermi
liquid, with the possibility for an intermediate critical state that possesses
some properties of the Moore-Read Pfaffian. These results are interpreted in
the two-component BCS model for Cauchy pairing with a tunneling constraint. We
comment on the conditions to be imposed on a system with fluctuating density in
order to achieve the stable Pfaffian phase.Comment: 10 pages, 7 figure
A Farey Tail for Attractor Black Holes
The microstates of 4d BPS black holes in IIA string theory compactified on a
Calabi-Yau manifold are counted by a (generalized) elliptic genus of a (0,4)
conformal field theory. By exploiting a spectral flow that relates states with
different charges, and using the Rademacher formula, we find that the elliptic
genus has an exact asymptotic expansion in terms of semi-classical
saddle-points of the dual supergravity theory. This generalizes the known
"Black Hole Farey Tail" of [1] to the case of attractor black holes.Comment: 36 pages, 3 figures, note adde
Quantum Kerr tunneling vacua on a -brane: An emergent Kerr black hole in five dimensions
We revisit a non-perturbative space-time curvature theory, underlying a two
form U(1) gauge dynamics, on a D4-brane. In particular, two different gauge
choices for a two form are explored underlying the dynamics of a geometric
torsion in a second order formalism. We obtain two non-extremal quantum Kerr
geometries in five dimensions on a pair of -brane in a type IIA
superstring theory. The quantum vacua are described by a vanishing torsion in a
gauge choice, underlying a geometric realization, on a non-BPS brane. It is
argued that the quantum Kerr vacua undergo tunneling and lead to a five
dimensional Kerr black hole in Einstein vacuum. A low energy limit in the
quantum Kerr vacua further re-assures an emergent Kerr black hole.Comment: 21 pages, 8 figure
Special geometry, black holes and Euclidean supersymmetry
We review recent developments in special geometry and explain its role in the
theory of supersymmetric black holes. To make this article self-contained, a
short introduction to black holes is given, with emphasis on the laws of black
hole mechanics and black hole entropy. We also summarize the existing results
on the para-complex version of special geometry, which occurs in Euclidean
supersymmetry. The role of real coordinates in special geometry is illustrated,
and we briefly indicate how Euclidean supersymmetry can be used to study
stationary black hole solutions via dimensional reduction over time.
This article is an updated and substantially extended version of the previous
review article `New developments in special geometry', hep-th/0602171.Comment: 39 pages, Contribution to the Handbook on Pseudo-Riemannian Geometry
and Supersymmtry, ed. V. Corte
Non-supersymmetric heterotic model building
We investigate orbifold and smooth Calabi-Yau compactifications of the
non-supersymmetric heterotic SO(16)xSO(16) string. We focus on such Calabi-Yau
backgrounds in order to recycle commonly employed techniques, like index
theorems and cohomology theory, to determine both the fermionic and bosonic 4D
spectra. We argue that the N=0 theory never leads to tachyons on smooth
Calabi-Yaus in the large volume approximation. As twisted tachyons may arise on
certain singular orbifolds, we conjecture that such tachyonic states are lifted
in the full blow-up. We perform model searches on selected orbifold geometries.
In particular, we construct an explicit example of a Standard Model-like theory
with three generations and a single Higgs field.Comment: 1+30 pages latex, 11 tables; v2: references and minor revisions
added, matches version published in JHE
Non-commutative World-volume Geometries: Branes on SU(2) and Fuzzy Spheres
The geometry of D-branes can be probed by open string scattering. If the
background carries a non-vanishing B-field, the world-volume becomes
non-commutative. Here we explore the quantization of world-volume geometries in
a curved background with non-zero Neveu-Schwarz 3-form field strength H = dB.
Using exact and generally applicable methods from boundary conformal field
theory, we study the example of open strings in the SU(2) Wess-Zumino-Witten
model, and establish a relation with fuzzy spheres or certain (non-associative)
deformations thereof. These findings could be of direct relevance for D-branes
in the presence of Neveu-Schwarz 5-branes; more importantly, they provide
insight into a completely new class of world-volume geometries.Comment: 19 pages, LaTeX, 1 figure; some explanations improved, references
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