Ofer Aharony

INTERACTIONS OF STRINGS AND D-BRANES FROM M THEORY

We discuss the relation between M theory and type II string theories. We show that, assuming “natural” interactions between membranes and fivebranes in M theory, the known interactions between strings and D-branes in type II string theories arise in appropriate limits. Our discussion of the interactions is purely at the classical level. We remark on issues associated with the M theory approach to enhanced gauge symmetries, which deserve further investigation.

Field theory questions for string theory answers

Abstract We discuss the field theory of 3-brane probes in F-theory compactifications in two configurations, generalizing the work of Sen and of Banks, Douglas and Seiberg. One configuration involves several parallel 3-brane probes in F-theory compactified on T 4 / Z 2 , while the other invloves a compactification of F-theory on T 6 / Z 2 × Z 2 (which includes intersecting D 4 singularities). In both cases string theory provides simple pictures of the space-time theory, whose implications for the 3-brane world-volume theories are discussed. In the second case the field theory on the probe is an unusual N = 1 superconformal theory, with exact electric-magnetic duality. Several open questions remain concerning the description of this theory.

String theory dualities from M-theory

Abstract We analyze how string theory dualities may be described in M-theory. T -dualities arise from scalar-vector dualities in the worldvolume of the membrane of M-theory. “Electric-magnetic” dualities arise from a duality transformation in M-theory compactified on a 3-torus, which takes the membrane into a fivebrane wrapped around the 3-torus. We show how the action of the membrane transforms into the action of the wrapped fivebrane by this fransformation. Other “electric-magnetic” dualities are related to this duality by compactifications and orbifoldings.

Note on anomalies in the AdS-CFT correspondence

We test the AdS-CFT correspondence in the case of a d=4 N=2 superconformal field theory by comparing chiral anomalies which are of order [ital N] in the [close quote]t Hooft large [ital N] limit. These include corrections of order 1/N to the conformal anomaly, thus testing the correspondence beyond the extreme large [ital N] limit. The field theory anomalies are reproduced by terms in the 7-brane effective action in the bulk. [copyright] [ital 1999] [ital The American Physical Society]

Exotic nonsupersymmetric gauge dynamics from supersymmetric QCD.

We extend Seiberg`s qualitative picture of the behavior of supersymmetric QCD to nonsupersymmetric models by adding soft supersymmetry-breaking terms. In this way we recover the standard vacuum of QCD with {ital N}{sub {ital f}} flavors and {ital N}{sub {ital c}} colors when {ital N}{sub {ital f}}{lt}{ital N}{sub {ital c}}. However, for {ital N}{sub {ital f}}{ge}{ital N}{sub {ital c}}, we find new exotic states---new vacua with spontaneously broken baryon number for {ital N}{sub {ital f}}={ital N}{sub {ital c}}, and a vacuum state with unbroken chiral symmetry for {ital N}{sub {ital f}}{gt}{ital N}{sub {ital c}} These exotic vacua contain massless composite fermions and, in some cases, dynamically generated gauge bosons. In particular Seiberg`s electric-magnetic duality seems to persist also in the presence of (small) soft supersymmetry breaking. We argue that certain, specially tailored, lattice simulations may be able to detect the novel phenomena. Most of the exotic behavior does not survive the decoupling limit of large SUSY-breaking parameters.

Exact electric-magnetic duality in N = 2 supersymmetric QCD theories

Abstract We analyze the Coulomb phase of theories of N =2 SQCD with SU ( N c ) gauge groups which are conjectured to have exact electric-magnetic duality. We discuss the duality transformation of the particle spectrum, emphasizing the differences between the general case and the SU (2) case. Some difficulties associated with the definition of the duality transformation for a general gauge group are discussed. We compute the classical monopole spectrum of these theories, and when it is possible we use it to check the consistency of the duality. Generally these theories may have phase transitions between strong and weak coupling, which prevent the semi-classical computation from being useful for checking the duality.

On the twisted G/H topological models

Abstract The twisted G/H models are constructed as twisted supersymmetric gauged WZW models. We analyze the case of G = SU( N ), H = SU( N 1 ) × … × SU( N n ) × U(1) r with rank(G) = rank(H), and discuss possible generalizations. We introduce a non-abelian bosonization of the (1, 0) ghost system in the adjoint of H and in G/H. By computing chiral anomalies in the latter picture we write the quantum action as a decoupled sum of “matter”, gauge and ghost sectors. The action is also derived in the unbosonized version. We invoke a free field parametrization and extract the space of physical states by computing the cohomology of Q , the sum of the BRST gauge-fixing charge and the twisted supersymmetry charge. For a given G we briefly discuss the relation between the various G/H models corresponding to different choices of H. The choice H = G corresponds to the topological G/G theory.

G/G models and WN strings

Abstract We derive the BRST cohomology of the G/G topological model for the case of A(1)N−1. It is shown that at level k= p q−N the latter describes the (p,q) WN minimal model coupled to WN gravity (plus some extra “topological sectors”).

String Theory Duals for Mass-deformed SO(N) and USp(2N) N = 4 SYM Theories

We generalize the results of Polchinski and Strassler regarding the N=1 preserving mass deformation of N=4SU(N) supersymmetric Yang-Mills (SYM) theories and its string theory dual to SO(N) and USp(2N) gauge groups. The string theory duals involve 5-branes wrapped on RP{sup 2}. In order to match with the field theory classification of vacua, the 3-brane charge carried by such 5-branes must be shifted by a half, and this follows from a conjectured generalization of results of Freed and Witten. Our results provide an elegant physical picture for the classification of classically massive vacua in the mass-deformed N=4 theories.

c=1 string theory as a topological G/G model

The physical states on the free field Fock space of the SL(2, R)/SL(2, R) model at any level are computed. Using a similarity transformation on QBRST, the cohomology of the latter is mapped into a direct sum of simpler cohomologies. We show a one to one correspondence between the states of the k = −1 model and those of the c = 1 string model. A full equivalence between the SL(2, R)/SL(2, R) and SL(2, R)/U(1) models at the level of their Fock space cohomologies is found.