429 research outputs found
Boost invariant quantum evolution of a meson field at large proper times
We construct asymptotic solutions of the functional Schroedinger equation for
a scalar field in the Gaussian approximation at large proper time. These
solutions describe the late proper time stages of the expansion of a meson gas
with boost invariant boundary conditions. The relevance of these solutions for
the formation of a disoriented chiral condensate in ultra relativistic
collisions is discussed.Comment: 9 pages, LATE
Temperature dependence of the response function of hot nuclear matter
The description of collective motion in nuclei at finite temperature using the framework of the random phase approximation is discussed. We focus on the special case of the isovector response function of hot nuclear matter using various effective Skyrme interactions
Response Function of Hot Nuclear Matter
We investigate the response function of hot nuclear matter to a small
isovector external field using a simplified Skyrme interaction reproducing the
value of the symmetry energy coefficient.
We consider values of the momentum transfer corresponding to the dipole
oscillation in heavy nuclei. We find that while at zero temperature the
particle hole interaction is almost repulsive enough to have a sharp (zero
sound type) collective oscillation, such is no longer the case at temperatures
of a few MeV. As a result a broadening of the dipole resonance occurs, leading
to its quasi disappearence by the time the temperature reaches 5 MeV. The
sensivity of the temperature evolution of the width when modifying the residual
interaction strength is also examined.Comment: 9 pages, IPNO/TH 94-15, DPT-IPN Orsay. Two figures available under
reques
Sur l'équivalence entre des types particuliers des équations de Navier-Stokes et de Schrödinger non linéaire
Nous étudions plusieurs généralisations de l'équivalence bien connue entre les équations de l'hydrodynamique et l'équation de Schrödinger non linéaire. Pour un fluide visqueux, irrotationnel, de viscosité cinématique constante, nous obtenons une équation de Schrödinger non linéaire, analogue à celle proposée par Kostin pour une description quantique de la friction. Nous traitons également le cas de l'écoulement rotationnel d'un tel fluide, et celui de l'écoulement à symétrie sphérique d'un fluide de viscosité constante
LIMITING TEMPERATURES OF EXCITED NUCLEI : STATIC AND DYNAMICAL ASPECTS
Some static and dynamical calculations of hot nuclei are discussed within the framework of the mean field approximation
Quantum generalization of the classical rotating solutions of the O(N) model
Analytic solutions of the mean field evolution equations for an N-component
scalar field with O(N) symmetry are presented. These solutions correspond to
rotations in isospin space. They represent generalizations of the classical
solutions obtained earlier by Anselm and Ryskin. As compared to classical
solutions new effects arise because of the coupling between the average value
of the field and quantum fluctuations.Comment: 14 pages, Late
Self Similar Solutions of the Evolution Equation of a Scalar Field in an Expanding Geometry
We consider the functional Schrodinger equation for a self interacting scalar
field in an expanding geometry. By performing a time dependent scale
transformation on the argument of the field we derive a functional Schrodinger
equation whose hamiltonian is time independent but involves a time-odd term
associated to a constraint on the expansion current. We study the mean field
approximation to this equation and generalize in this case, for interacting
fields, the solutions worked out by Bunch and Davies for free fields.Comment: 8 pages, Latex, IPNO/TH 94-3
Isovector response function of hot nuclear matter with Skyrme interactions
We investigate the role of the effective nucleon-nucleon interaction in the
description of giant dipole resonances in hot nuclei. For this purpose we
calculate the response function of hot nuclear matter to a small isovector
external perturbation using various effective Skyrme interactions. We find that
for Skyrme forces with an effective mass close to unity an undamped zero sound
mode occurs at zero temperature. This mode gives rise in finite nuclei
(calculated via the Steinwedel-Jenssen model) to a resonance whose energy
agrees with the observed value. We find that zero sound disappears at a
temperature of a few MeV, leaving only a broad peak in the dipole strength. For
Skyrme forces with a small value of the effective mass (0.4- 0.5), there is no
zero sound at zero temperature but only a weak peak located too high in energy.
The strength distribution in this case is nearly independent of temperature and
shows small collective effects. The relevance of these results for the
saturation of photon multiplicities observed in recent experiments is pointed
out.Comment: 33 pages Email: [email protected]
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