77 research outputs found
How parametric resonance mechanism follows quench mechanism in disoriented chiral condensate
We show how parametric resonance mechanism follows quench mechanism in the
classical linear sigma model. The parametric resonance amplifies long
wavelength modes of the pion for more than . The shifting from the
quench mechanism to the parametric resonance mechanism is described by a time
dependent quantity. After the quench mechanism is over, that quantity has an
oscillating part, which causes the parametric resonance. Since its frequency is
: pion mass), very long wavelength modes such as k = 40 MeV
of the pion are amplified by the parametric resonance.Comment: LaTeX, 10 page
Two Pion Correlations as a Possible Experimental Probe for Disoriented Chiral Condensates
We discuss two-pion correlations as a possible experimental probe into
disoriented chiral condensates. In particular, we point out that the
iso-singlet squeezed states of the BCS type have peculiar two-particle
correlations in the back-to-back and the identical momentum configurations
which should be detectable experimentally. We motivate the examination of the
squeezed state by showing that such state naturally appears in a final stage of
nonequilibrium phase transitions via the parametric resonance mechanism
proposed by Mr\'owczy\'nski and M\"uller.Comment: RevTeX 13 pages, 2 Postscript figures include
Large-N Collective Field Theory Applied to Anyons in Magnetic Fields
We present a large- collective field formalism for anyons in external
magnetic fields interacting with arbitrary two-body potential. We discuss how
the Landau level is reproduced in our framework. We apply it to the soluble
model for anyons proposed by Girvin et al., and obtain the dispersion relation
of collective modes for arbitrary statistical parameters.Comment: 10 pages(Plain TeX) TMUP-HEL-930
Parametric resonance at the critical temperature in high energy heavy ion collisions
Parametric resonance in soft modes at the critical temperature () in
high energy heavy ion collisions is studied in the case when the temperature
() of the system is almost constant for a long time. By deviding the fields
into three parts, zero mode (condensate), soft modes and hard modes and
assuming that the hard modes are in thermal equilibrium, we derive the equation
of motion for soft modes at . Enhanced modes are extracted by
comparing with the Mathieu equation for the condensate oscillating along the
sigma axis at . It is found that the soft mode of fields at
about 174 MeV is enhanced.Comment: 8 pages, 1 figure Some statements and equations are modified to
clarif
Quantum description for a chiral condensate disoriented in a certain direction in isospace
We derive a quantum state of the disoriented chiral condensate dynamically,
considering small quantum fluctuations around a classical chiral condensate
disoriented in a certain direction in isospace. The obtained
nonisosinglet quantum state has the characteristic features; (i) it has the
form of the squeezed state, (ii) the state contains not only the component of
pion quanta in the direction but also the component in the
perpendicular direction to and (iii) the low momentum pions in the
state violate the isospin symmetry. With the quantum state, we calculate the
probability of the neutral fraction depending on the time and the pion's
momentum, and find that the probability has an unfamiliar form. For the low
momentum pions, the parametric resonance mechanism works with the result that
the probability of the neutral fraction becomes the well known form
approximately and that the charge fluctuation is small.Comment: 19 page
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
Description of a domain by a squeezed state in a scalar field theory
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.Comment: 10 pages, 5 figures, a typographical error in the reference is
correcte
Parametric amplification with a friction in heavy ion collisions
We study the effects of the expansion of the system and the friction on the
parametric amplification of mesonic fields in high energy heavy ion collisions
within the linear model . The equation of motion which is similar to
Mathieu equation is derived to describe the time development of classical
fields in the last stage of a heavy ion collision after the freezeout time. The
enhanced mode is extracted analytically by comparison with Mathieu equation and
the equation of motion is solved numerically to examine whether soft modes will
be enhanced or not. It is found that the strong peak appears around 267 MeV in
the pion transverse momentum distribution in cases with weak friction and high
maximum temperature. This enhancement can be extracted by taking the ratio
between different modes in the pion transverse momentum distribution.Comment: 10 pages, 9 figures LaTeX: appendix adde
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