Cosmological Solutions to the Lithium Problem
  The abundance of primordial lithium is derived from the observed spectroscopy
of metal-poor stars in the galactic halo. However, the observationally inferred
abundance remains at about a factor of three below the abundance predicted by
standard big bang nucleosynthesis (BBN). The resolution of this dilemma can be
either astrophysical (stars destroy lithium after BBN), nuclear (reactions
destroy lithium during BBN), or cosmological, i.e. new physics beyond the
standard BBN is responsible for destroying lithium. Here, we overview a variety
of possible cosmological solutions, and their shortcomings. On the one hand, we
examine the possibility of physical processes that modify the velocity
distribution of particles from the usually assumed Maxwell-Boltzmann
statistics. A physical justification for this is an inhomogeneous spatial
distribution of domains of primordial magnetic field strength as a means to
reduce the primordial lithium abundance. Another possibility is that scattering
with the mildly relativistic electrons in the background plasma alters the
baryon distribution to one resembling a Fermi-Dirac distribution. We show that
neither of these possibilities can adequately resolve the lithium problem. A
number of alternate hybrid models are discussed including a mix of neutrino
degeneracy, unified dark matter, axion cooling, and the presence of decaying
and/or charged supersymmetric particles.
