Distributions of nonsupersymmetric flux vacua

We continue the study of the distribution of nonsupersymmetric flux vacua in IIb string theory compactified on Calabi-Yau manifolds, as in hep-th/0404116. We show that the basic structure of this problem is that of finding eigenvectors of the matrix of second derivatives of the superpotential, and that many features of the results are determined by features of the generic ensemble of such matrices, the CI ensemble of Altland and Zirnbauer originating in mesoscopic physics. We study some simple examples in detail, exhibiting various factors which can favor low or high scale supersymmetry breaking.Comment: 28 pages, JHEP Latex format. v2: a correction further favoring high scale, v3: minor clarification

Attractors at Weak Gravity

We study the attractor mechanism in low energy effective D=4, N=2 Yang-Mills theory weakly coupled to gravity, obtained from the effective action of type IIB string theory compactified on a Calabi-Yau manifold. Using special Kahler geometry, the general form of the leading gravitational correction is derived, and from this the attractor equations in the weak gravity limit. The effective Newton constant turns out to be spacetime-dependent due to QFT loop and nonperturbative effects. We discuss some properties of the attractor solutions, which are gravitationally corrected dyons, and their relation with the BPS spectrum of quantum Yang-Mills theory. Along the way, we obtain a satisfying description of Strominger's massless black holes, moving at the speed of light, free of pathologies encountered in some earlier proposals.Physic

TASI lectures on complex structures

These lecture notes give an introduction to a number of ideas and methods that have been useful in the study of complex systems ranging from spin glasses to D-branes on Calabi-Yau manifolds. Topics include the replica formalism, Parisi's solution of the Sherrington-Kirkpatrick model, overlap order parameters, supersymmetric quantum mechanics, D-brane landscapes and their black hole duals.Comment: 109 pages, 16 figure

Supergravity flows and D-brane stability

We investigate the correspondence between existence/stability of BPS states in type II string theory compactified on a Calabi-Yau manifold and BPS solutions of four dimensional N=2 supergravity. Some paradoxes emerge, and we propose a resolution by considering composite configurations. This in turn gives a smooth effective field theory description of decay at marginal stability. We also discuss the connection with 3-pronged strings, the Joyce transition of special Lagrangian submanifolds, and Pi-stability.Comment: 40 pages, 13 figures, reference adde

Grassmann Matrix Quantum Mechanics

We explore quantum mechanical theories whose fundamental degrees of freedom are rectangular matrices with Grassmann valued matrix elements. We study particular models where the low energy sector can be described in terms of a bosonic Hermitian matrix quantum mechanics. We describe the classical curved phase space that emerges in the low energy sector. The phase space lives on a compact Kahler manifold parameterized by a complex matrix, of the type discovered some time ago by Berezin. The emergence of a semiclassical bosonic matrix quantum mechanics at low energies requires that the original Grassmann matrices be in the long rectangular limit. We discuss possible holographic interpretations of such matrix models which, by construction, are endowed with a finite dimensional Hilbert space.Comment: 25 pages + appendice