Effective Field Theory in the Early Universe课件.pptVIP

Effective Field Theory in the Early Universe Inflation, Axions and Baryogenesis Michael Dine Berkeley Oct. 2004 (Collaborations with A. Anisimov, T. Banks, M. Berkooz, M. Graesser, T. Volansky) 精品文档 In very early universe cosmology, one is exploring physics at scales well above those which have been probed experimentally; the relevant laws of nature are at best conjectural. How to proceed? What can we hope to learn? Might hope to guess the correct theory. More likely, success will come from looking at classes of theories (Supersymmetric? Large dimensions? Axions?) Hopefully with connections to experiment. Crucial tool: effective action, appropriate to the relevant scale of energies, temperature, curvature 精品文档 Problems to which we might apply these methods: Dark matter Inflation (superluminal expansion, fluctuations) Baryogenesis In each of these cases, early analyses took some renormalizable field theory, and analyzed as if space-time were flat. More realistic analysis often yields a qualitatively different picture. Different possible phenomena; sometimes problems arise, sometimes problems are resolved. 精品文档 Today we will consider: Axions as Dark Matter Moduli in cosmology Inflation We will do axions in the greatest detail. 精品文档 Axions and the Strong CP Problem Strong CP Problem: QCD is a very successful theory. But aside from the coupling constant, it has an additional parameter: In QED, such a term would have no effect, but in QCD, can show generates CP violating phenomena, e.g. 精品文档 Why is q so small? Axion solution (Peccei, Quinn, Wilczek, Weinberg): Postulate field, a(x), symmetry: QCD generates a potential for a(x). If qeff =0, QCD preserves CP, so ignoring weak interactions, minimum of axion potential will lie at qeff=0. Can calculate the axion potential (current algebra): 精品文档 A light particle: Constraints from particle searches, red giants: Cosmology can potentially constrain as well. 精品文档 The axi