45 research outputs found
Direct Mediation of Meta-Stable Supersymmetry Breaking
The supersymmetric SU(Nc) Yang-Mills theory coupled to Nf matter fields in
the fundamental representation has meta-stable vacua with broken supersymmetry
when Nc < Nf < 3/2 Nc. By gauging the flavor symmetry, this model can be
coupled directly to the standard model. We show that it is possible to make a
slight deformation to the model so that gaugino masses are generated and the
Landau pole problem can be avoided. The deformed model has simple realizations
on intersecting branes in string theory, where various features of the
meta-stable vacua are encoded geometrically as brane configurations.Comment: 22 pages, 4 figures, a reference added, version to appear in PR
Baby Universes in String Theory
We argue that the holographic description of four-dimensional BPS black holes
naturally includes multi-center solutions. This suggests that the holographic
dual to the gauge theory is not a single AdS_2 times S^2 but a coherent
ensemble of them. We verify this in a particular class of examples, where the
two-dimensional Yang-Mills theory gives a holographic description of the black
holes obtained by branes wrapping Calabi-Yau cycles. Using the free fermionic
formulation, we show that O(e^{-N}) non-perturbative effects entangle the two
Fermi surfaces. In an Euclidean description, the wave-function of the
multi-center black holes gets mapped to the Hartle-Hawking wave-function of
baby universes. This provides a concrete realization, within string theory, of
effects that can be interpreted as the creation of baby universes. We find
that, at least in the case we study, the baby universes do not lead to a loss
of quantum coherence, in accord with general arguments.Comment: 39 pages, 7 figure
Summing up D-Instantons
We investigate quantum corrections to the moduli space for hypermultiplets
for type IIA near a conifold singularity. We find a unique quantum deformation
based on symmetry arguments which is consistent with a recent conjecture. The
correction can be interpreted as an infinite sum coming from multiple wrappings
of the Euclidean D-branes around the vanishing cycle.Comment: 8 pages, harvmac; a reference added, typoes correcte
Hartle-Hawking Wave-Function for Flux Compactifications
We argue that the topological string partition function, which has been known
to correspond to a wave-function, can be interpreted as an exact
``wave-function of the universe'' in the mini-superspace sector of physical
superstring theory. This realizes the idea of Hartle and Hawking in the context
of string theory, including all loop quantum corrections. The mini-superspace
approximation is justified as an exact description of BPS quantities. Moreover
this proposal leads to a conceptual explanation of the recent observation that
the black hole entropy is the square of the topological string wave-function.
This wave-function can be interpreted in the context of flux compactification
of all spatial dimensions as providing a physical probability distribution on
the moduli space of string compactification. Euclidean time is realized
holographically in this setup.Comment: 37 pages, 2 figure
Black Hole Attractors and the Topological String
A simple relationship of the form Z_BH = |Z_top|^2 is conjectured, where Z_BH
is a supersymmetric partition function for a four-dimensional BPS black hole in
a Calabi-Yau compactification of Type II superstring theory and Z_top is a
second-quantized topological string partition function evaluated at the
attractor point in moduli space associated to the black hole charges. Evidence
for the conjecture in a perturbation expansion about large graviphoton charge
is given. The microcanonical ensemble of BPS black holes can be viewed as the
Wigner function associated to the wavefunction defined by the topological
string partition function.Comment: 32 pages, harvma
Wilson Loops in Large N Theories
Talk presented at Strings '99 in Potsdam, Germany (July 19 - 24, 1999).Comment: 11 pages; submitted to Proceedings of Strings '9
Wall Crossing As Seen By Matrix Models
The number of BPS bound states of D-branes on a Calabi-Yau manifold depends
on two sets of data, the BPS charges and the stability conditions. For D0 and
D2-branes bound to a single D6-brane wrapping a Calabi-Yau 3-fold X, both are
naturally related to the Kahler moduli space M(X). We construct unitary
one-matrix models which count such BPS states for a class of toric Calabi-Yau
manifolds at infinite 't Hooft coupling. The matrix model for the BPS counting
on X turns out to give the topological string partition function for another
Calabi-Yau manifold Y, whose Kahler moduli space M(Y) contains two copies of
M(X), one related to the BPS charges and another to the stability conditions.
The two sets of data are unified in M(Y). The matrix models have a number of
other interesting features. They compute spectral curves and mirror maps
relevant to the remodeling conjecture. For finite 't Hooft coupling they give
rise to yet more general geometry \widetilde{Y} containing Y.Comment: 44 pages, 9 figures, published versio
Aspects of Large N Gauge Theory Dynamics as Seen by String Theory
In this paper we explore some of the features of large N supersymmetric and
nonsupersymmetric gauge theories using Maldacena's duality conjectures. We
shall show that the resulting strong coupling behavior of the gauge theories is
consistent with our qualitative expectations of these theories. Some of these
consistency checks are highly nontrivial and give additional evidence for the
validity of the proposed dualities.Comment: 31 pages, LaTeX, 11 eps figures, typos correcte
Wilson Loops and Minimal Surfaces
The AdS/CFT correspondence suggests that the Wilson loop of the large N gauge
theory with N=4 supersymmetry in 4 dimensions is described by a minimal surface
in AdS_5 x S^5. We examine various aspects of this proposal, comparing gauge
theory expectations with computations of minimal surfaces. There is a
distinguished class of loops, which we call BPS loops, whose expectation values
are free from ultra-violet divergence. We formulate the loop equation for such
loops. To the extent that we have checked, the minimal surface in AdS_5 x S^5
gives a solution of the equation. We also discuss the zig-zag symmetry of the
loop operator. In the N=4 gauge theory, we expect the zig-zag symmetry to hold
when the loop does not couple the scalar fields in the supermultiplet. We will
show how this is realized for the minimal surface.Comment: 51 pages, 7 figure