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]