Squeezed coherent state representation of scalar field and particle production in the early universe. (Q1580713)

Particle production is a quantum phenomenon which results from vacuum fluctuations in a strong gravitational field. In this paper authors use the squeezed coherent state introduced by Fan and Xiao for the calculation of particle production in the early universe. Squeezing of the vacuum is achieved by means of the background gravitational field, which plays the role of a vacuum amplifier. The presented calculation shows that the vacuum expectation value of the stress-energy tensor of scalar field contains additional term in comparing with the classical zero- point energy term. The authors calculate the expectation value of the stress-energy tensor by assuming that the field is in a special type of squeezed coherent states. The calculations is made for a general form of a background cosmological metric which is spatially homogeneous, possibly anisotropic, and topologically a three-torus.