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It has recently been speculated that the end state of a collapsing universeis a tachyonic big crunch. The time reversal of this process would be theemergence of an expanding universe from a tachyonic big bang. In thisframework, we study the emergence of cosmological fluctuations. In particular,we compare the amplitude of the perturbations at tne end of the tachyon phasewith what would be obtained assuming the usual vacuum initial conditions. Wefind that cosmological fluctuations emerge in a thermal state. We comment onthe relation to the trans-Planckian problem of inflationary cosmology.

Emergence of Fluctuations from a Tachyonic Big Bang