Coherent and squeezed condensates in massless $\lambda {\phi }^4$ theory

Abstract

Generalizing the Bogoliubov model of a weakly non-ideal Bose gas to massless $\lambda {\phi }^4$ theory we show that spontaneous breaking of symmetry occurs due to condensation in a coherent vacuum % which is energetically favoured compared to the perturbative one. and leads to a vacuum energy density which is lower than that obtained by Coleman and Weinberg using the one-loop effective potential method. We discuss the alternative of a squeezed condensate and find that for the massless $\lambda {\phi }^4$ theory spontaneous symmetry breaking to a squeezed vacuum does not occur.

13 pages, Latex