72,285 research outputs found
Chiral transition and mesonic excitations for quarks with thermal masses
We study the effect of a thermal quark mass, m_T, on the chiral phase
transition and mesonic excitations in the light quark sector at finite
temperature in a simple chirally-symmetric model. We show that while nonzero
m_T lowers the chiral condensate, the chiral transition remains of second
order. It is argued that the mesonic excitations have large decay rate at
energies below 2m_T, owing to the Landau damping of the quarks and the van Hove
singularities of the collective modes.Comment: 5 pages, 6 figures, typos correcte
Multifragmentation of non-spherical nuclei : Analysis of central Xe + Sn collisions at 50 MeV/nucl
The influence of shape of expanding and rotating source on various
characteristics of the multifragmentation process is studied. The analysis is
based on the extension of the statistical microcanonical multifragmentation
model. The comparison with the data is done for central Xe+Sn collisions at 50
A MeV as measured by INDRA Collaboration.Comment: 9 pages, 2 figures; Talk given at the XXVII International Workshop on
Gross Properties of Nuclei and Nuclear Excitation, Hirschegg (Austria),
January 17 - 23, 199
Freezing Transition in Decaying Burgers Turbulence and Random Matrix Dualities
We reveal a phase transition with decreasing viscosity at \nu=\nu_c>0
in one-dimensional decaying Burgers turbulence with a power-law correlated
random profile of Gaussian-distributed initial velocities
\sim|x-x'|^{-2}. The low-viscosity phase exhibits non-Gaussian
one-point probability density of velocities, continuously dependent on \nu,
reflecting a spontaneous one step replica symmetry breaking (RSB) in the
associated statistical mechanics problem. We obtain the low orders cumulants
analytically. Our results, which are checked numerically, are based on
combining insights in the mechanism of the freezing transition in random
logarithmic potentials with an extension of duality relations discovered
recently in Random Matrix Theory. They are essentially non mean-field in nature
as also demonstrated by the shock size distribution computed numerically and
different from the short range correlated Kida model, itself well described by
a mean field one step RSB ansatz. We also provide some insights for the finite
viscosity behaviour of velocities in the latter model.Comment: Published version, essentially restructured & misprints corrected. 6
pages, 5 figure
Thermal mass and dispersion relations of quarks in the deconfined phase of quenched QCD
Temporal quark correlation functions are analyzed in quenched lattice QCD for
two values of temperature above the critical temperature (Tc) for
deconfinement, T=1.5Tc and 3Tc. A two-pole ansatz for the quark spectral
function is used to determine the bare quark mass and the momentum dependence
of excitation spectra on large lattices of size up to 128^3x16. The dependence
of the quark correlator on these parameters as well as the finite volume
dependence of the excitation energies are analyzed in detail in order to
examine the reliability of our analysis. Our results suggest the existence of
quasi-particle peaks in the quark spectrum. We furthermore find evidence that
the dispersion relation of the plasmino mode has a minimum at non-zero momentum
even in the non-perturbative region near Tc. We also elaborate on the
enhancement of the quark correlator near the chiral limit which is observed at
T=1.5Tc on about half of the gauge configurations. We attribute this to the
presence of near zero-modes of the fermion matrix that are associated with
non-trivial topology of the gauge configurations.Comment: 12pages, 7 figure
Spectral properties of massless and massive quarks coupled with massive boson at finite temperature
We study the properties of massless and massive quarks coupled with a scalar
and pseudoscalar boson at finite temperature in Yukawa models at the one-loop
order. The behavior of the spectral function and the pole structure of the
propagator are analyzed as functions of temperature and the quark mass
. It is shown that the three-peak structure of the spectral function found
in a previous work for massless quarks is formed at temperatures comparable to
the boson mass even for finite , but gradually ceases to exist as
becomes larger. We identify the three poles of the quark propagator
corresponding to the collective excitations of the quark in the complex energy
plane. It is shown that the three trajectories made by the poles along with a
variation of undergo a structural rearrangement at a critical quark mass
when is increased. This suggests that the physics content of the
collective quark excitations is changed in a drastic way at this point. The
results are nicely accounted for with the notion of the level mixing induced by
a resonant scattering of the massive boson with quarks and holes of thermally
excited anti-quarks.Comment: 16 pages, 36 eps figures. Accepted for publication in Physical Reviw
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