Micha Berkooz

BRANES INTERSECTING AT ANGLES

Abstract We show that configurations of multiple D-branes related by SU(N) rotations will preserve unbroken supersymmetry. This includes cases in which two D-branes are related by a rotation of arbitrarily small angle, and we discuss some of the physics of this. In particular, we discuss a way of obtaining 4D chiral fermions on the intersection of D-branes. We also rephrase the condition for unbroken supersymmetry as the condition that a ‘generalized holonomy group’ associated with the brane configuration and manifold is reduced, and relate this condition (in type IIA string theory) to a condition in eleven dimensions.

Anomalies, dualities, and topology of D = 6 N = 1 superstring vacua

We consider various aspects of compactifications of the Type 1/heterotic Spin(32)/Z2 theory on K3. One family of such compactifications includes the standard embedding of the spin connection in the gauge group, and is on the same moduli space as the compactification of the heterotic E8 × E8 theory on K3 with instanton numbers (8,16). Another class, which includes an orbifold of the Type I theory recently constructed by Gimon and Polchinski and whose field theory limit involves some topological novelties, is on the moduli space of the heterotic E8 × E8 theory on K3 with instanton numbers (12,12). These connections between Spin(32)/Z2 and E8 × E8 models can be demonstrated by T-duality, and permit a better understanding of nonperturbative gauge fields in the (12,12) model. In the transformation between Spin(32)/Z2 and E8 × E8 models, the strong/weak coupling duality of the (12,12) E8 × E8 model is mapped to T-duality in the Type I theory. The gauge and gravitational anomalies in the Type I theory are canceled by an extension of the Green-Schwarz mechanism.

Matrix description of M-theory on T4 and T5

Abstract We study the Matrix theory description of M-theory compactified on T4 and T5. M-theory on T4 is described by the six dimensional (2,0) fixed point field theory compactified on a five torus, T 5 . For M-theory on T5 we suggest the existence of a new theory which is compactified on a T 5 . The IR description of this theory is given by the (2,0) theory with a compactified moduli space. This new theory appears to be a new kind of a non-critical string theory. Clearly, these two descriptions differ from the “standard” Super-Yang-Mills on the dual torus prescription.

A D = 4 N = 1 orbifold of type I strings

We consider the propagation of type I open superstrings on orbifolds with four non-compact dimensions and N = 1 supersymmetry. In this paper, we concentrate on a non-trivial Z2 × Z2 example. We show that consistency conditions, arising from tadpole cancellation and algebraic sources, require the existence of three sets of Dirichlet 5-branes. We discuss fully the enhancements of the spectrum when these 5-branes intersect. An amusing attribute of these models is the importance of the tree-level (in type I language) superpotential to the consistent relationship between Higgsing and the motions of 5-branes.

Five-branes in M(atrix) theory

Abstract We propose a construction of five-branes which fill both light-cone dimensions in Banks, Fischler, Shenker and Susskinds matrix model of M theory. We argue that they have the correct long-range fields and spectrum of excitations. We prove Dirac charge quantization with the membrane by showing that the five-brane induces a Berry phase in the membrane world-volume theory, with a familiar magnetic monopole form.

Membrane dynamics in M(atrix)-theory

Abstract We analyze some of the kinematical and dynamical properties of flat infinite membrane solutions in the conjectured M theory proposed by Banks, Fischler, Shenker and Susskind. In particular, we compute the long range potential between membranes and anti-membranes, and between membranes and gravitons, and compare it with the supergravity results. We also discuss membranes with finite relative longitudinal velocities, providing some evidence for the 11-dimensional Lorentz invariance of the theory.

The dual of supersymmetric SU(2k) with an antisymmetric tensor and composite dualities

Abstract We suggest a dual to an SU (2 k ) SUSY gauge theory containing an antisymmetric tensor, n F fundamentals and n F anti-fundamentals. This is done by expanding the theory into an equivalent description with two gauge groups and then performing known duality transformations on each gauge group separately. Chiral operators, mass perturbations and flat directions are discussed.

Cosmological moduli problem, supersymmetry breaking, and stability in postinflationary cosmology

We review scenarios that have been proposed to solve the cosmological problem caused by moduli in string theory, the postmodern Polonyi problem (PPP). In particular, we discuss the difficulties encountered by the apparently ``trivial`` solution of this problem, in which moduli masses are assumed to arise from nonperturbative, SUSY-preserving, dynamics at a scale higher than that of SUSY breaking. This suggests a powerful {ital cosmological} {ital vacuum} {ital selection} {ital principle} in superstring theory. However, we argue that if one eschews the possibility of cancellations between different exponentials of the inverse string coupling, the mechanism described above cannot stabilize the dilaton. Thus, even if supersymmetric dynamics gives mass to the other moduli in string theory, the dilaton mass must be generated by SUSY breaking, and dilaton domination of the energy density of the Universe cannot be avoided. We conclude that the only proposal for solving the PPP that works is the intermediate scale inflation scenario of Randall and Thomas. However, we point out that all extant models have ignored unavoidably large inhomogeneities in the cosmological moduli density at very early times, and speculate that the effects associated with nonlinear gravitational collapse of these inhomogeneities may serve as an efficient mechanismmorexa0» for converting moduli into ordinary matter. As an important by-product of this investigation we show that in a postinflationary universe minima of the effective potential with a negative cosmological constant are not stationary points of the classical equations of scalar field cosmology. Instead, such points lead to catastrophic gravitational collapse of that part of the Universe which is attracted to them. Thus postinflationary cosmology dynamically chooses non-negative values of the cosmological constant. This implies that supersymmetry {ital must} be broken in any sensible inflationary cosmology. (Abstract Truncated)«xa0less

Near-horizon solutions for D3-branes ending on 5-branes

We construct the type IIB supergravity solutions describing D3-branes ending on 5branes, in the near-horizon limit of the D3-branes. Our solutions are holographically dual to the 4dN = 4SU(N) super-Yang-Mills (SYM) theory on a half-line, at largeN and large ’t Hooft coupling, with various boundary conditions that preserve half of the supersymmetry. The solutions are limiting cases of the general solutions with the same symmetries constructed in 2007 by D’Hoker, Estes and Gutperle. The classication of our solutions matches exactly with the general classication of boundary conditions for D3-branes ending on 5-branes by Gaiotto and Witten. We use the gravity duals to compute the one-point functions of some chiral operators in theN = 4 SYM theory on a half-line at strong coupling, and nd that they do not match with the expectation values of the same operators with the same boundary conditions at small ’t Hooft coupling. Our solutions may also be interpreted as the gravity duals of 4d N = 4 SYM on AdS4, with various boundary conditions.

Dual descriptions of SO(10) supersymmetric gauge theories with arbitrary numbers of spinors and vectors

We examine the low-energy structure of N=1 supersymmetric SO(10) gauge theory with matter chiral superfields in N{sub Q} spinor and N{sub f} vector representations. We construct a dual to this model based upon an SU(N{sub f}+2N{sub Q}{minus}7){times}Sp(2N{sub Q}{minus}2) gauge group without utilizing deconfinement methods. This product theory generalizes all previously known Pouliot-type duals to SO(N{sub c}) models with spinor and vector matter. It also yields large numbers of new dual pairs along various flat directions. The dual description of the SO(10) theory satisfies multiple consistency checks including an intricate renormalization group flow analysis which links it with Seiberg{close_quote}s duality transformations. We discuss its implications for building grand-unified theories that contain all standard model fields as composite degrees of freedom. {copyright} {ital 1997} {ital The American Physical Society}