; Brandenberger, Robert
; Zhang, Xinmin] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Xue, Wei
; Brandenberger, Robert] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada
; [Brandenberger, Robert
; Zhang, Xinmin] CAS, TPCSF, Beijing 100049, Peoples R China
; [Brandenberger, Robert] CAS, Kavli Inst Theoret Phys, Beijing 100190, Peoples R China
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.