Flat Directions and Baryogenesis in Supersymmetric Theories

Flat directions are a generic feature of supersymmetric theories. They are of cosmological interest because they can lead to coherent production of scalars. In the early universe such flat directions could be dangerous due to the potentially large energy density and the late decay of the associated scalars when they have only $1/M_p$ couplings (Polonyi problem). On the other hand, flat directions among the standard model fields can carry baryon number and lead to a possible mechanism for baryogenesis (Affleck Dine baryogenesis). When considering the cosmological consequences of the flat directions, it is important to take into account the soft potential with curvature of order the Hubble constant due to supersymmetry breaking in the early universe. In this talk, we discuss flat directions, their potential cosmological implications focusing on Affleck-Dine baryogenesis, and how the standard picture of their evolution must be modified in the presence of the large supersymmetry breaking in the early universe.Comment: 11 pages, LATEX, talk given in XXXth Rencontres de Moriond, ``Electroweak Interactions and Unified Theories

The Shape of Gravity

In a nontrivial background geometry with extra dimensions, gravitational effects will depend on the shape of the Kaluza-Klein excitations of the graviton. We investigate a consistent scenario of this type with two positive tension three-branes separated in a five-dimensional Anti-de Sitter geometry. The graviton is localized on the ``Planck'' brane, while a gapless continuum of additional gravity eigenmodes probe the {\it infinitely} large fifth dimension. Despite the background five-dimensional geometry, an observer confined to either brane sees gravity as essentially four-dimensional up to a position-dependent strong coupling scale, no matter where the brane is located. We apply this scenario to generate the TeV scale as a hierarchically suppressed mass scale. Arbitrarily light gravitational modes appear in this scenario, but with suppressed couplings. Real emission of these modes is observable at future colliders; the effects are similar to those produced by {\it six} large toroidal dimensions.Comment: 8 pages, 1 figur