628 research outputs found
Inclusion of Quantum Fluctuations in Wave Packet Dynamics
We discuss a method by which quantum fluctuations can be included in
microscopic transport models based on wave packets that are not energy
eigenstates. By including the next-to-leading order term in the cumulant
expansion of the statistical weight, which corresponds to the wave packets
having Poisson energy distributions, we obtain a much improved global
description of the quantum statistical properties of the many-body system. In
the case of atomic nuclei, exemplified by 12C and 40Ca, the standard
liquid-drop results are reproduced at low temperatures and a phase
transformation to a fragment gas occurs as the temperature is raised. The
treatment can be extended to dynamical scenarios by means of a Langevin force
emulating the transitions between the wave packets. The general form of the
associated transport coefficients is derived and it is shown that the
appropriate microcanonical equilibrium distribution is achieved in the course
of the time evolution. Finally, invoking Fermi's golden rule, we derive
specific expressions for the transport coefficients and verify that they
satisfy the fluctuation-dissipation theorem.Comment: uuencoded revtex body and 8 ps figures (16 pages total
Baryon-strangeness correlations: a diagnostic of strongly interacting matter
The correlation between baryon number and strangeness elucidates the nature
of strongly interacting matter, such as that formed transiently in high-energy
nuclear collisions. This diagnostic can be extracted theoretically from lattice
QCD calculations and experimentally from event-by-event fluctuations. The
analysis of present lattice results above the critical temperature severely
limits the presence of q-qbar bound states, thus supporting a picture of
independent (quasi)quarks.Comment: 4 pages, 2 eps figures, Revised: several sign typos have been fixed
(the PRL version is correct
Collective and Egoless Consciousness Significance for Philosophy of Science and for the Mind-Body Problem
Animal Mind as Approached by the Transpersonal: Notion of Collective Conscious Experience
The discussion of animal mind in this paper is based on an idealist philosophy contending that
only conscious experience is real, based on the transpersonal notion of collective conscious experience.
The latter has earlier been explained by the author as experience referred to a group of
humans as the subject, the We. Here it is contended that also a group of humans and animals
can be seen as the subject of collective conscious experiences. The author argues that the notion
of collective conscious experience provides a possibility for studying the problems of animal mind
and the related human problem of “other minds” in a detailed and rational way
Dynamical simulation of DCC formation in Bjorken rods
Using a semi-classical treatment of the linear sigma model, we simulate the
dynamical evolution of an initially hot cylindrical rod endowed with a
longitudinal Bjorken scaling expansion (a ``Bjorken rod''). The field equation
is propagated until full decoupling has occurred and the asymptotic many-body
state of free pions is then obtained by a suitable Fourier decomposition of the
field and a subsequent stochastic determination of the number of quanta in each
elementary mode. The resulting transverse pion spectrum exhibits visible
enhancements below 200 MeV due to the parametric amplification caused by the
oscillatory relaxation of the chiral order parameter. Ensembles of such final
states are subjected to various event-by-event analyses. The factorial moments
of the multiplicity distribution suggest that the soft pions are
non-statistical. Furthermore, their emission patterns exhibit azimuthal
correlations that have a bearing on the domain size in the source. Finally, the
distribution of the neutral pion fraction shows a significant broadening for
the soft pions which grows steadily as the number of azimuthal segments is
increased. All of these features are indicative of disoriented chiral
condensates and it may be interesting to apply similar analyses to actual data
from high-energy nuclear collision experiments.Comment: 38 pages total, incl 26 ps figures ([email protected]
Fission-fragment mass distributions from strongly damped shape evolution
Random walks on five-dimensional potential-energy surfaces were recently
found to yield fission-fragment mass distributions that are in remarkable
agreement with experimental data. Within the framework of the Smoluchowski
equation of motion, which is appropriate for highly dissipative evolutions, we
discuss the physical justification for that treatment and investigate the
sensitivity of the resulting mass yields to a variety of model ingredients,
including in particular the dimensionality and discretization of the shape
space and the structure of the dissipation tensor. The mass yields are found to
be relatively robust, suggesting that the simple random walk presents a useful
calculational tool. Quantitatively refined results can be obtained by including
physically plausible forms of the dissipation, which amounts to simulating the
Brownian shape motion in an anisotropic medium.Comment: 14 pages, 11 ps figure
Effect of friction on disoriented chiral condensate formation
We have investigated the effect of friction on the DCC domain formation. We
solve the Newton equation of motion for the O(4) fields, with quenched initial
condition. The initial fields are randomly distributed in a Gaussian form. In
one dimensional expansion, on the average, large DCC domains can not be formed.
However, in some particular orbits, large instabilities may occur. This
possibility also greatly diminishes with the introduction of friction. But, if
the friction is large, the system may be overdamped and then, there is a
possibility of large DCC domain formation in some events.Comment: 9 pages, including figure
Dissipation, noise and DCC domain formation
We investigate the effect of friction on domain formation in disoriented
chiral condensate. We solve the equation of motion of the linear sigma model,
in the Hartree approximation, including a friction and a white noise term. For
quenched initial condition, we find that even in presence of noise and
dissipation domain like structure emerges after a few fermi of evolution.
Domain size as large as 5 fm can be formed.Comment: 7 pages, 3 figure
Dileptons from Disoriented Chiral Condensates
Disoriented chiral condensates or long wavelength pionic oscillations and
their interaction with the thermal environment can be a significant source of
dileptons. We calculate the yield of such dilepton production within the linear
sigma model, both in a quantal mean-field treatment and in a semi-classical
approximation. We then illustrate the basic features of the dilepton spectrum
in a schematic model. We find that dilepton yield with invariant mass near and
below due to the soft pion modes can be up to two orders of
magnitude larger than the corresponding equilibrium yield.Comment: 22 pages, 8 figures, uses epsf-styl
Resonance model study of strangeness production in pp collisions
Results for the energy dependence of the elementary kaon production cross
sections in proton-proton collisions are reported. Calculations are performed
within an extended version of the resonance model which was used for the
previous studies of elementary kaon production in pion-nucleon and
pion- collisions. Although the model treatment is within the {\it
empirical} tree level (observed widths for the resonances are used), it is
fully relativistic, and includes all relevant baryon resonances up to 2 GeV.
One of the purposes of this study is to provide the results for the simulation
codes of subthreshold kaon production in heavy ion collisions. This is the
first, consistent study of the elementary kaon production reactions including
both and () collisions on the same footing.
Comparisons are made between the calculated results and the existing
semi-empirical parametrizations which are widely used for the simulation codes,
as well as the experimental data.Comment: 10 pages with 5 postscript figures, Latex, revised version for
publication in Phys. Lett.
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