Cold big-bang cosmology as a counterexample to several anthropic arguments

Abstract

A general Friedmann big-bang cosmology can be specified by fixing a half-dozen cosmological parameters such as the photon-to-baryon ratio ${\ensuremath{\eta}}_{\ensuremath{\gamma}},$ the cosmological constant $\ensuremath{\Lambda},$ the curvature scale R, and the amplitude Q of (assumed scale-invariant) primordial density fluctuations. There is currently no established theory as to why these parameters take the particular values we deduce from observations. This has led to proposed ``anthropic'' explanations for the observed value of each parameter as the only value capable of generating a universe that can host intelligent life. In this paper, I explicitly show that the requirement that the universe generates Sun-like stars with planets does not fix these parameters, by developing a class of cosmologies (based on the classical ``cold big-bang'' model) in which some or all of the cosmological parameters differ by orders of magnitude from the values they assume in the standard hot big-bang cosmology, without precluding in any obvious way the existence of intelligent life. I also give a careful discussion of the structure and context of anthropic arguments in cosmology, and point out some implications of the cold big-bang model's existence for anthropic arguments concerning specific parameters.