159 research outputs found

### Nonequilibrium chiral dynamics by the time dependent variational approach with squeezed states

We investigate the inhomogeneous chiral dynamics of the O(4) linear sigma
model in 1+1 dimensions using the time dependent variational approach in the
space spanned by the squeezed states. We compare two cases, with and without
the Gaussian approximation for the Green's functions. We show that mode-mode
correlation plays a decisive role in the out-of-equilibrium quantum dynamics of
domain formation and squeezing of states.Comment: 5 pages, 4 figures. RevTex, version to appear in Phys. Rev. C. Rapid
Communicatio

### Parametric Resonance versus Forced Oscillation in Time-Evolution of Quantum Meson Fields

The time-evolution of quantum meson fields in O(4)-linear sigma model is
treated approximately. It is shown that the amplification of the amplitudes of
pion modes with low momenta occurs by means of both the parametric resonance
and the forced oscillation.Comment: 8 pages, no figure, using PTPTeX styl

### Scalar and Pseudoscalar Glueball Masses within a Gaussian Wavefunctional Approximation

The lowest scalar and pseudoscalar glueball masses are evaluated by means of
the time-dependent variational approach to the Yang-Mills gauge theory without
fermions in the Hamiltonian formalism within a Gaussian wavefunctional
approximation. The glueball mass is calculated as a pole of the propagator for
a composite glueball field which consists of two massless gluons. The glueball
propagator is here evaluated by using the linear response theory for the
composite external glueball field. As a result, a finite glueball mass is
obtained through the interaction between two massless gluons, in which the
glueball mass depends on the QCD coupling constant g in the nonperturbative
form.Comment: 24 pages, 3 figure

### A Possible Extension of a Trial State in the TDHF Theory with Canonical Form in the Lipkin Model

With the aim of the extension of the TDHF theory in the canonical form in the
Lipkin model, the trial state for the variation is constructed, which is an
extension of the Slater determinant. The canonicity condition is imposed to
formulate the variational approach in the canonical form. A possible solution
of the canonicity condition is given and the zero-point fluctuation induced by
the uncertainty principle is investigated. As an application, the ground state
energy is evaluated.Comment: 15 pages, 1 figure, using PTPTeX styl

### Variational Approach to the Chiral Phase Transition in the Linear Sigma Model

The chiral phase transition at finite temperature is investigated in the
linear sigma model, which is regarded as a low energy effective theory of QCD
with three momentum cutoff, in the variational method with the Gaussian
approximation in the functional Schroedinger picture. It is shown that the
Goldstone theorem is retained and the meson pair excitations are automatically
included by taking into account the linear response to the external fields. It
is pointed out that the behavior of chiral phase transition depends on the
three-momentum cutoff, which leads to the careful treatment of the problem.Comment: 14 pages, 5 figures, using PTPTeX cl

### Effective Potential Study of the Chiral Phase Transition in a QCD-like Theory

We construct the effective potential for a QCD-like theory using the
auxiliary field method. The chiral phase transition exhibited by the model at
finite temperature and the quark chemical potential is studied from the
viewpoint of the shape change of the potential near the critical point. We
further generalize the effective potential so as to have quark number and
scalar quark densities as independent variables near the tri-critical point.Comment: 17 pages, 9 figures, using PTPTeX.cl

### Time-Evolution of a Collective Meson Field by the Use of a Squeezed State

A time-evolution of quantum meson fields is investigated in a linear sigma
model by means of the time-dependent variational approach with a squeezed
state. The chiral condensate, which is a mean field of the quantum meson
fields, and quantum fluctuations around it are treated self-consistently in
this approach. The attention is payed to the description of the relaxation
process of the chiral condensate, where the energy stored in the mean field
configuration flows to the fluctuation modes. It is shown that the quantum
fluctuations play an important role to describe this relaxation process.Comment: 18 pages, 22 postscript figures, uses PTPTeX.st

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