Solving the cosmological moduli problem with weak scale inflation

Abstract

Many models of supersymmetry breaking, including those motivated by superstring theory, involve “flat” directions which lead to particles with weak scale mass and Planck scale suppressed couplings. Coherent production of such particles can dominate the energy density in the early universe and destroy the successful predictions of nucleosynthesis. We also point out that producing a baryon density in such a scenario generally leads to an overproduction of the lightest supersymmetric particle if R-parity is conserved. We show that these problems may be solved by reducing the coherent condensate of dangerous particles through a brief period of inflation with a Hubble constant of the order of the weak scale. Furthermore the inflaton potential for such an inflation arises naturally from the same assumptions which lead to the cosmological problems, namely the existence of “flat” directions. Successful baryogenesis and preservation of density fluctuations for large scale structure formation are also possible in this scenario.