Cosmological structure produced by a phase transition near nuclear density

This paper shows that a cold expanding universe naturally produces stars at high redshift. A homogeneous universe composed of low-entropy matter (S< or approx. =1) spontaneously shatters into large pieces as it passes through a period of metastability during a phase transition. An approximate theory shows that the nucleation of rupture by quantum tunneling always produces cracks that are ''large'' (i.e., much larger than the mean particle separation) when they meet, of the order of 10-3 of the sound horizon length; this gives the size of typical fragments. At nuclear density, matter probably passes through a first-order phase transition as a result of pion condensation or neutron solidification, which produces fragments between approx.10-10 and 10-6 M/sub sun/ at a redshift zroughly-equal1014. This lumpiness generates density fluctuations which grow by the usual gravitational instability on scales larger than the Jeans mass M/sub J/roughly-equal(2--10)(S+1)2 M/sub sun/. Thus, one naturally expects in this mass range to form at high redshift, 100< or approx. =z< or approx. =107. This would be a ''pregalactic'' or ''Population III'' generation of stars; because M> or approx. =2 M/sub sun/, none would be burning now, but their remnants may form the dark matter in galactic halos and clusters. These stars must also be held accountable for the production of the microwave background, galaxies, and, probably, helium. The model makes simple predictions about the expected large-scale anisotropy in the microwave background which differ from standard theories postulating fluctuations in the initial state and/or a primordial origin for the entropy. Other less direct tests are also proposed