Evidence for Compact Dark Matter in Galactic Halos

Clumped dark matter arises naturally within the framwork of generic cosmological dark matter models. Invoking the existence of dark matter clumps can also solve may unexplained mysteries in astrophysics and geology or geophysics, eg. the galactic gamma-ray halo and the periodic terrestrial flood basalt volcanic episodes. Clumped dark matter is dynamically stable to friction and will not heat the disk. Such clumps may have already been discovered in the form of dwarf spheroidals, and further searches are encouraged by the results of this paper.Comment: Revised Version, includes new relevant references, Latex File, 16 pages, no figure

Duality Invariant Superstring Actions

Worldsheet supersymmetric string action is written in duality invariant form for flat as well as curved backgrounds. First the action in flat backgrounds is written by introducing auxiliary fields. We also give the superfield form of this action and obtain the offshell supersymmetry algebra. The action has a modified Lorentz invariance and supersymmetry and reduces to the usual form when the auxiliary fields are eliminated using their equations of motion. Supersymmetric nonlinear sigma model in curved backgrounds is also written in manifestly duality invariant form when the background metric and tortion fields are independent of some of the coordinates.Comment: 14 pages, LaTeX, IP/BBSR/94-3