Spin Correlations in Ultracold Atoic Gases and Hot Dense matter

Spin Correlations in quantum liquids and gases play an important role in a variety of different situations. I shall describe work on interaction-induced shifts of spectral lines in cold gases, which are important as a disgnostic tool in basic physics and also of technological interest because they limit the accuracy of atomic clocks. Neutrinos emitted in dense matter in stellar collapse and in neutron stars are thought to be a key ingredient in understanding supernovae explosions and the cooling of neutron stars. Spin correlations in matter are a major contributor to neutrino emission, absorption, and scattering processes, and I shall report on recent progress in obtaining better estimats of these rates.