An anthropic solution to the cosmological moduli problem
  Light moduli fields, gravitationally coupled scalar fields with no classical
potential and which are expected to emerge as remnants from string theory
compactification, are dangerous to cosmology in that 1. their late-time decays
may disrupt successful Big Bang Nucleosynthesis (BBN), 2. they may decay into
gravitino pairs which result in violation of BBN constraints or overproduction
of lightest SUSY particles (LSPs, assumed to constitute at least a portion of
the dark matter in the universe) and 3. they may decay directly into LSPs,
resulting in gross DM overproduction. Together, these constitute the
cosmological moduli problem (CMP). The combined effects require lightest
modulus mass m_\phi >~10^4 TeV, and if the lightest modulus mass m_\phi is
correlated with the SUSY breaking scale m_{3/2}, then the underlying SUSY model
would be highly unnatural. We present a solution to the CMP wherein the
lightest modulus initial field strength \phi_0 is anthropically selected to be
\phi_0\sim 10^{-7}m_P by the requirement that the dark matter-to-baryonic
matter ratio be not-too-far removed from its present value so that sufficient
baryons are present in the universe to create observers. In this case, instead
of dark matter overproduction via neutralino reannihilation at the modulus
decay temperature, the neutralinos inherit the reduced moduli number density,
thereby gaining accord with the measured dark matter relic density.
