From SYM Perturbation Theory to Closed Strings in Matrix Theory

For the purpose of better understanding the AdS/CFT correspondence it is useful to have a description of the theory for all values of the 't Hooft coupling, and for all $N$. We discuss such a description in the framework of Matrix theory for SYM on D4-branes, which is given in terms of quantum mechanics on the moduli space of solutions of the Nahm equations. This description reduces to both SYM perturbation theory and to closed string perturbation theory, each in its appropriate regime of validity, suggesting a way of directly relating the variables in the two descriptions. For example, it shows explicitly how holes in the world-sheets of the 't Hooft expansion close to give closed surfaces.Comment: 19 page

A Supergravity Dual of a (1,0) Field Theory in Six Dimensions

We suggest a supergravity dual for the $(1,0)$ superconformal field theory in six dimensions which has $E_8$ global symmetry. Compared to the description of the (2,0) field theory, the 4-sphere is replaced by a 4-hemisphere, or by orbifolding the 4-sphere.Comment: 5 pages, Harvmac. Typos corrected, References correcte

Near Hagedorn Dynamics of NS Fivebranes, or A New Universality Class of Coiled Strings

We analyze the thermodynamics of NS 5-branes as the temperature approaches the NS 5-branes' Hagedorn temperature, and conclude that the dynamics of ``Little String Theory'' is a new universality class of interacting strings. First we point out how to vary the temperature of the near extremal solution by taking into account $g_s$ corrections. The Hagedorn temperature is shown to be a limiting temperature for the theory. We then compare the thermodynamics to that of a toy model made of free strings and find basic discrepancies. This suggests a need for a new class of string interactions. We suggest that this new universality class is characterized by a strong attractive self-intersection interaction, which causes strings to be coiled. This model might also explain why ``Little String Theories'' exist in at most 5+1 dimensions.Comment: 37 pages, important signs in section 6.4 corrected, references adde

Splitting the Wino Multiplet by Higher-Dimensional Operators in Anomaly Mediation

In a class of AMSB models, the splitting in the Wino multiplet turns out to be very small, such as the often-quoted 170 MeV in minimal AMSB, which originates from MSSM loops. Such a small mass gap is potentially a window into higher scale physics, as it may be sensitive to higher-dimensional operators. We show that still within AMSB one can get a much larger splitting in the Wino multiplet--a few GeV--if the scale of the new physics is comparable to the gravitino mass (which is indeed often the scale of new physics in anomaly mediation).Comment: 18 pages; v2: references added, matching journal versio

New IR Dualities in Supersymmetric Gauge Theory in Three Dimensions

We present nontrivial examples of d=3 gauge theories with sixteen and eight supercharges which are infrared dual at special points in the moduli space. This duality is distinct from mirror symmetry. To demonstrate duality we construct the gauge theories of interest using D2-branes and orientifolds and then consider their lift to M-theory. We also discuss the strong coupling limit of orientifold two-planes and orbifolds of orientifold six-planes.Comment: 15 pages, harvmac, 1 embedded ps figure; a reference has been adde

IR Dynamics of d=2, N=(4,4) Gauge Theories and DLCQ of "Little String Theories"

We analyze the superconformal theories (SCFTs) which arise in the low-energy limit of N=(4,4) supersymmetric gauge theories in two dimensions, primarily the Higgs branch SCFT. By a direct field theory analysis we find a continuum of "throat"-like states localized near the singularities of the Higgs branch. The "throat" is similar to the "throat" found in the Coulomb branch of the same theories, but the full superconformal field theories of the two branches are different. A particular example is the SCFT of the R^4/Z_2 sigma model with zero theta angle. In the application of the Higgs branch SCFTs to the DLCQ description of "little string theories" (LSTs), the "throat" continuum is identified with the continuum of "throat" states in the holographic description of the LSTs. We also match the descriptions of the string interactions (in the "throat" region) in the DLCQ and holographic descriptions of the N=(2,0) LSTs.Comment: 37 pages, harvmac. v2: very minor change