518 research outputs found
Time-Evolution of Collective Meson Fields and Amplification of Quantum Meson Modes in Chiral Phase Transition
The time evolution of quantum meson fields in the O(4) linear sigma model is
investigated in a context of the dynamical chiral phase transition. It is shown
that amplitudes of quantum pion modes are amplified due to both mechanisms of a
parametric resonance and a resonance by the forced oscillation according to the
small oscillation of the chiral condensate in the late time of chiral phase
transition.Comment: 4 pages; Talk presented at the XVIth International Conference on
Particles and Nuclei (PANIC02), Sep. 30 - Oct. 4, 2002, Osaka, Japan, to
appear in Nuclear Physics
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
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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