Primordial Element Formation, Primordial Magnetic Fields, and the Isotropy of the Universe

Abstract

A detailed discussion is presented of homogeneous cosmological models which (i) have two equivalent "tangential" directions and one inequivalent "longitudinal" direction at each point in spacetime; (ii) have zero rotation; (iii) contain a perfect fluid obeying an equation of state p = p(p); and (iv) contain a magnetic field frozen into the matter and pointing in the longitudinal direction. By means of these cosmological models it is shown that, if the big-bang general-relativistic theory of the universe is correct, and if the galactic magnetic fields which are observed today were primordial in origin, then the universe was probably very anisotropic in its early stages These cosmological models are also used to evaluate the implications of astronomical observations for the isotropy of the universe. It is shown that the current 3 per cent limit on the anisotropy of the cosmic microwave radiation places limits on the large-scale isotropy of the universe, which are many orders of magnitude stronger than limits inferred from the observed isotropy of extragalactic redshifts Finally, an analysis is presented of primordial element formation in anisotropic cosmological models. One of the chief conclusions is this: if there has been a negligible amount of intergalactic H ii ever since the primordial photons were sufficiently energetic to ionize hydrogen, and if the universe is Euclidean but anisotropic in its large-scale geometry, then the current limit of 3 per cent on the microwave a…