10,157 research outputs found
QCD Thermodynamics with Improved Actions
The thermodynamics of the SU(3) gauge theory has been analyzed with tree
level and tadpole improved Symanzik actions. A comparison with the continuum
extrapolated results for the standard Wilson action shows that improved actions
lead to a drastic reduction of finite cut-off effects already on lattices with
temporal extent . Results for the pressure, the critical temperature,
surface tension and latent heat are presented. First results for the
thermodynamics of four-flavour QCD with an improved staggered action are also
presented. They indicate similarly large improvement factors for bulk
thermodynamics.Comment: Talk presented at LATTICE96(finite temperature) 4 pages, LaTeX2e
file, 6 eps-file
Improved Actions for QCD Thermodynamics on the Lattice
Finite cut-off effects strongly influence the thermodynamics of lattice
regularized QCD at high temperature in the standard Wilson formulation. We
analyze the reduction of finite cut-off effects in formulations of the
thermodynamics of gauge theories with three different and
improved actions. We calculate the energy density and pressure on
finite lattices in leading order weak coupling perturbation theory
() and perform Monte Carlo simulations with improved
actions at non-zero . Already on lattices with temporal extent
we find a strong reduction of finite cut-off effects in the high
temperature limit, which persists also down to temperatures a few times the
deconfinement transition temperature.Comment: 20 pages, 3 Postscript figure
The three flavour chiral phase transition with an improved quark and gluon action in lattice QCD
The finite-temperature chiral phase transition is investigated for three
flavours of staggered quarks on a lattice of temporal extent N_t=4. In the
simulation we use an improved fermion action which reduces rotational symmetry
breaking of the quark propagator (p4-action), include fat-links to improve the
flavour symmetry and use the tree level improved (1,2) gluon action. We study
the nature of the phase transition for quark masses of ma=0.025, ma=0.05 and
ma=0.1 on lattices with spatial sizes of 8^3 and 16^3.Comment: LATTICE98(hightemp), 3 pages, 7 figures, LaTeX2e-File, espcrc2.st
Humoral Antibodies in Patients After Renal Homotransplantation.
Humoral antibodies have been demonstrated by antiglobulin consumption tests to be present in the serum of virtually all patients after renal homotransplantation. The most completely characterized was a ÎłG immunoglobulin distinct from the Forssman antibody which reacts against sheep but not against human red cell antigens, and which absorbs selectively against panels of human liver, kidney or white blood cells. This antibody appeared within a few days or weeks after transplantation, usually shortly after a rejection episode, and was more or less continuously detectable thereafter. The antibody was found in all of 10 patients studied during the first 4 post-transplant months, and in 13 of 14 patients tested from 4 months to more than 2 years after operation. Preliminary observations are included on another humoral antibody which does not react with sheep RBC stromata, but which can also be measured with a modified antiglobulin consumption test. The latter antibody was less commonly demonstrable, but it also exhibited specific absorption characteristics when tested against a panel of leukocytes obtained from volunteers. The implications of these findings are discussed in relation to the possible value of such sera for histocompatibility typing, as well as the possible role of such antibodies in promoting homograft enhancement
Chiral Symmetry in Two-Color QCD at Finite Temperature
We study the chiral symmetry in two-color QCD with N massless flavors at
finite temperature, using an effective theory. For the gauge group SU(2), the
chiral symmetry is enlarged to SU(2N), which is then spontaneously broken to
Sp(2N) at zero temperature. At finite temperature, and when the axial anomaly
can be neglected, we find a first order phase transition occurring for two or
more flavors. In the presence of instantons, the symmetry restoration
unambiguously remains first order for three or more massless flavors. These
results could be relevant for lattice studies of chiral symmetry at finite
temperature and density.Comment: 10 pages, Revte
Non-Gaussian Statistics of Multiple Filamentation
We consider the statistics of light amplitude fluctuations for the
propagation of a laser beam subjected to multiple filamentation in an amplified
Kerr media, with both linear and nonlinear dissipation. Dissipation arrests the
catastrophic collapse of filaments, causing their disintegration into almost
linear waves. These waves form a nearly-Gaussian random field which seeds new
filaments. For small amplitudes the probability density function (PDF) of light
amplitude is close to Gaussian, while for large amplitudes the PDF has a long
power-like tail which corresponds to strong non-Gaussian fluctuations, i.e.
intermittency of strong optical turbulence. This tail is determined by the
universal form of near singular filaments and the PDF for the maximum
amplitudes of the filaments
Origin of Borromean systems
The complex energies of the three-body resonances for one infinitely heavy
particle and two non-interacting light particles are the sum of the two
contributing two-body complex resonance energies. The bound state of a
Borromean system originates from a resonance when the third interaction is
introduced, a finite mass is allowed and proper angular momentum coupling is
included. The relative importance of these contributions are investigated and
the resulting structure of Borromean systems are traced back to the two-body
continuum properties. The and states in He result from
neutron-core p-states and the ground and first excited state of Li
originate from neutron-core and -states.Comment: Physics Letters B, in pres
Future directions in kaonic atom physics
Recent progress and open problems in kaonic atom physics are presented. A
connection between phenomenological deep potentials and the underlying
interaction is established as well as the need for a theory for multinucleon
absorption of kaons. absorption at rest to specific
hypernuclei states is briefly discussed.Comment: 6 pages, 3 figures, proceedings of the EXA2011 conference, to appear
in Hyperfine Interaction
- âŠ