Thermal Fluctuations and Bouncing Cosmologies
  We study the conditions under which thermal fluctuations generated in the
contracting phase of a non-singular bouncing cosmology can lead to a
scale-invariant spectrum of cosmological fluctuations at late times in the
expanding phase. We consider point particle gases, holographic gases and string
gases. In the models thus identified, we also study the thermal
non-Gaussianities of the resulting distribution of inhomogeneities. For regular
point particle radiation, we find that the background must have an equation of
state $w = 7/3$ in order to obtain a scale-invariant spectrum, and that the
non-Gaussianities are suppressed on scales larger than the thermal wavelength.
For Gibbons-Hawking radiation, we find that a matter-dominated background
yields scale-invariance, and that the non-Gaussianities are large. String gases
are also briefly considered.
