  The author attempted to describe a domain by using a squeezed state in
quantum field theory. An extended squeeze operator was used to construct the
state. In a scalar field theory, the author described a domain that the
distributions of the condensate and of the fluctuation are Gaussian. The
momentum distribution, chaoticity and correlation length were calculated. It
was found that the typical value of the momentum is about the inverse of the
domain size, and that the chaoticity reflects the ratio of the size of the
squeeze region to that of the coherent region. The results indicate that the
quantum state of a domain is surmised by these quantities under the assumption
that the distributions are Gaussian. As an example, this method was applied to
a pion field, and the momentum distribution and the chaoticity were shown.
