Shmuel Elitzur

Remarks on the canonical quantization of the Chern-Simons-Witten theory

Abstract We comment on some aspects of the canonical quantization of the Chern-Simons-Witten theory. We carry out explicitly the quantization on several interesting surfaces. The connection to the related two dimensional theory is illustrated from different points of view.

Branes and N = 1 duality in string theory

Abstract We propose a construction of dual pairs in four dimensional N = 1 supersymmetric Yang-Mills theory using branes in type IIA string theory.

Some global aspects of string compactifications

Nearly flat bosonic string vacua are examined. An analogy between compactification in string theory with tachyonic condensation and the Landau theory of solidification is pointed out. A generic frustration resulting from the incompatibility of the topologies of the plane and that of the sphere is discussed. This is a global obstacle to obtain perturbatively fixed points on compact space-time. Some relations between global properties of the space-time manifolds and the various world-sheet couplings are obtained. These properties serve also as guides to study and solve perturbatively c ⩾ d conformal backgrounds.

Brane dynamics and N=1 supersymmetric gauge theory

Abstract We discuss some aspects of the relation between space-time properties of branes in string theory, and the gauge theory on their world-volume, for models invariant under four supercharges in three and four dimensions. We show that a simple set of rules governing brane dynamics reproduces many features of gauge theory. We study theories with U ( N c ), SO ( N c ), and Sp ( N c ) gauge groups and matter in the fundamental and two-index tensor representations, and use the brane description to establish Seibergs electric-magnetic duality for these models.

Algebraic aspects of matrix theory on Td

Abstract We study the exceptional U -duality group E d of M-theory compactified on a d -torus and its representations using Matrix theory. We exhibit the E d structure and show that p -branes wrapped or unwrapped around the longitudinal direction form representations of the U -duality group together with other, more mysterious, states.

Remarks on non-Abelian duality

Abstract A class of two-dimensional globally scale-invariant, but not conformally invariant, theories is obtained. These systems are identified in the process of discussing global and local scaling properties of models related by duality transformations, based on non-semisimple isometry groups. The construction of the dual partner of a given model is followed through; non-local as well as local versions of the former are discussed.

D-Branes in the Background of NS Fivebranes

We study the dynamics of D-branes in the near-horizon geometry of NS fivebranes. This leads to a holographically dual description of the physics of D-branes ending on and/or intersecting NS5-branes. We use it to verify some properties of such D-branes which were deduced indirectly in the past, and discuss some instabilities of non-supersymmetric brane configurations. Our construction also describes vacua of Little String Theory which are dual to open plus closed string theory in asymptotically linear dilaton spacetimes.

Aspects of bosonization in string theory

Abstract Non-supersymmetric string theories with world-sheet fermions are considered. Different consistent ways of summing over the spin structures lead to various vacua of the bosonic theory. In particular, fermionic models with O(2 n ) × O(2 n ) symmetry are equivalent to bosonic systems with non-zero constant torsion. Fermionic models with the non-simply laced symmetry groups O(2 n − 1) × O(2 n − 1) are bosonized to a string propagating on an orbifold.

D-branes on a gauged WZW model

Abstract The algebraic classification of Cardy for boundary states on a G / H coset CFT of a compact group G , is geometrically realized on the corresponding manifold resulting from gauging the WZW model. The branes consist of H orbits of quantized G conjugacy classes shifted by quantized H conjugacy classes.

Branes, orientifolds and chiral gauge theories

Abstract We discuss some aspects of the physics of branes in the presence of orientifolds and the corresponding world-volume gauge dynamics. We show that at strong coupling orientifolds sometimes turn into bound states of orientifolds and branes, and give a world-sheet argument for the flip of the sign of an orientifold plane split into two disconnected parts by an NS5-brane. We also describe the moduli space of vacua of N = 2 supersymmetric gauge theories with symplectic and orthogonal gauge groups, and analyze a set of four-dimensional N = 1 supersymmetric gauge theories with chiral matter content using branes.