2,402 research outputs found
Generalized Green-Schwarz mechanism in F theory
We derive the anomaly 8-form of 6-dimensional gauge theories arising in F
theory compactifications on elliptic Calabi-Yau threefolds. The result allows
to determine the matter content of certain such theories in terms of
intersection numbers on the base of elliptic fibration. We also discuss gauge
theories on 7-branes with double point singularities on the worldvolume.
Applications to Type II compactifications on Hirzebruch surfaces and are
outlined.Comment: 11 pages, harvmac. Normalization of (tr R^2)^2 term correcte
F-theory, Geometric Engineering and N=1 Dualities
We consider geometric engineering of N=1 supersymmetric QFTs with matter in
terms of a local model for compactification of F-theory on Calabi-Yau fourfold.
By bringing 3-branes near 7-branes we engineer N=1 supersymmetric
gauge theory with flavors in the fundamental. We identify the Higgs
branch of this system with the instanton moduli space on the compact four
dimensional space of the 7-brane worldvolume. Moreover we show that the
Euclidean 3-branes wrapped around the compact part of the 7-brane worldvolume
can generate superpotential for as well as lead to quantum
corrections to the moduli space for . Finally we argue that Seiberg's
duality for N=1 supersymmetric QCD may be mapped to T-duality exchanging
7-branes with 3-branes.Comment: 15 page
Instantons on D-branes
We consider type IIA compactification on . We show that the instanton
subsectors of the worldvolume of 4-branes wrapped around lead to a
Hagedorn density of BPS states in accord with heterotic-type IIA duality in 6
dimensions. We also find evidence that the correct framework to understand the
results of Nakajima on the appearance of affine Kac-Moody algebras on the
cohomology of moduli space of instantons on ALE spaces is in the context of
heterotic-type IIA string duality.Comment: 11 page
Theory of K\"ahler Gravity
In this paper we discuss the connection on a space of TCFT's that
appears in the context of background (in)dependence. We formulate a family of
{\it target space field theories} with a similar connection on it. Each theory
is a gauge theory (with the gauge group being in the case of
-fold). It describes deformations of K\"ahler structures much like Kodaira
Spencer theory describes deformations of the complex structures. It is
manifestly background independent. It appears to be a target space field theory
for supersymmetric quantum mechanics
Exact Counting of Black Hole Microstates
The exact entropy of two-charge supersymmetric black holes in N=4 string
theories is computed to all orders using Wald's formula and the supersymmetric
attractor equations with an effective action that includes the relevant higher
curvature terms. Classically, these black holes have zero area but the
attractor equations are still applicable at the quantum level. The quantum
corrected macroscopic entropy agrees precisely with the microscopic counting
for an infinite tower of fundamental string states to all orders in an
asymptotic expansion.Comment: 4 pages, latex, minor change
Chern-Simons from Dirichlet 2-brane instantons
In the vicinity of points in Calabi-Yau moduli space where there are
degenerating three-cycles the low energy effective action of type IIA string
theory will contain significant contributions arising from membrane instantons
that wrap around these three-cycles. We show that the world-volume description
of these instantons is Chern-Simons theory.Comment: 8 pages, harvmac, scaling of coupling in with Chern-Simons
coupling corrected, reference adde
Quantum Hamiltonian Reduction of Super Kac-Moody Algebra II
The quantum Hamiltonian reduction on the OSp(1,2) super Kac-Moody algebra is
described in the BRST formalism. Using a free field representation of the KM
currents, the super Kac-Moody algebra is shown to be reduced to a
superconformal one via the Hamiltonian reduction. This reduction is manifestly
supersymmetric because of supersymmetric constraints imposed on the algebra.Comment: 16 page
D-Branes and Topological Field Theories
In the presence of a D-brane a string theory develops a new subsector. We
show that for curved D-branes the corresponding sector is a (partially twisted)
topological field theory. We use this result to compute the degeneracy of
2-branes wrapped around cycles as well as 3-branes wrapped around CY
threefold vanishing 3-cycles. In both cases we find the degeneracy is in accord
with expectation. The counting of BPS states of a gas of 0-branes in the
presence of a 4-brane in is considered and it is noted that the effective
0-brane charge is shifted by 1, due to a quantum correction. This is in accord
with string duality and the fact that left-moving ground state energy of
heterotic string starts at . We also show that all the three different
topological twistings of four dimensional Yang-Mills theory do arise from
curved three-branes embedded in different spaces (Calabi-Yau manifolds and
manifolds with exceptional holonomy groups).Comment: 22 page
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