The dielectric formulation for the excitations in a bose-condensed liquid is developed from the viewpoint of the spontaneous breakdown of the phase symmetry. The excitations are hybridized between the sound and the atomic excitations in the normal state through the condensate. The sound and the...

Taking into account the random scatterings due to random eigenfrequencies and random hopping matrices, we obtain the correlation functions for phonon and sound density fluctuations, which yield three and one entropy fluctuation modes at high frequencies, and three and one thermal conductivity at...

Taking into account the scattering processes due to random eigenfrequencies and random hopping matrices, we calculate the correlation functions of density fluctuations associated with the particle--hole pairs in the intraband and interband. The correlation functions for the intraband yield sound...

We perform the dimensional reduction of the linear σ model at one-loop level. The effective potential of the reduced theory obtained from the integration over the nonzero Matsubara frequencies is exhibited. Thermal mass and coupling constant renormalization constants are given, as well as the...