Evidence for String Substructure

We argue that the behavior of string theory at high temperature and high longitudinal boosts, combined with the emergence of p-branes as necessary ingredients in various string dualities, point to a possible reformulation of strings, as well as p-branes, as composites of bits. We review the string-bit models, and suggest generalizations to incorporate p-branes.Comment: Latex file, 21 pages, 11 postscript figure

Galilean Supersymmetry in 2+1 Dimensions

We review work done in collaboration with C.B. Thorn on Super-Galilei invariant field theory and its application to the reformulation of superstring theory in terms of constituent superstring-bits.Comment: 10 pages, Latex. Talk given at the workshop on low dimensional field theory, Telluride, C

A note on D0-branes and instantons in 5d supersymmetric gauge theories

We refine a previous proposal for obtaining the multi-instanton partition function from the supersymmetric index of the 1d supersymmetric gauge theory on the worldline of D0-branes. We provide examples where the refinements are crucial for obtaining the correct result.Comment: 30 pages, 6 figures. Typos correcte

Branes and 2d N=(2,2) gauge theories with orthogonal and symplectic groups

We construct two-dimensional N=(2,2) supersymmetric gauge theories with orthogonal and symplectic groups using branes and orientifold planes in Type IIA string theory. A number of puzzles regarding the construction, including the effect of exchanging NS5-branes on an orientifold 2-plane, are resolved by lifting the configurations to M theory. The low energy properties and conjectured dualities of these theories are reproduced in the M-brane description. A similar construction of N=(4,4) theories with orthogonal and symplectic groups leads to new duality conjectures for these theories.Comment: 22 pages, 27 figures. Type IIA linking number computation corrected in section 4.5. Clarified and expanded the discussion of N=(4,4) dualities in section 5. References adde

Anomalous radius shift in AdS(4)/CFT(3)

We study higher order corrections to the radius/M2-brane charge of AdS_4 x S^7/Z_k. There are two sources of corrections: one from the orbifold singularity of C^4/Z_k, and the other from the discrete torsion associated with the homology 3-cycle H_3(S^7/Z_k,Z) = Z_k. We give a precise formula for the charge shift. These corrections are relevant, for example, at two loops in the AdS_4 x CP^3 sigma model, and therefore for the strong coupling test of the all loop Bethe ansatz.Comment: 16 pages; v2: The Type IIA D-brane probe calculation has been corrected, and now agrees with the M theory calculation. Appendix on conventions for RR fields and D-brane actions added. Note added on a possible correction due to a parity anomaly. References adde