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 $N_\tau=4$. 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 $SU(N)$ gauge theories with three different $O(a^2)$ and $O(a^4)$ improved actions. We calculate the energy density and pressure on finite lattices in leading order weak coupling perturbation theory ($T\rightarrow \infty$) and perform Monte Carlo simulations with improved $SU(3)$ actions at non-zero $g^2$. Already on lattices with temporal extent $N_\tau=4$ 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 γG 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 $0^+$ and $2^+$ states in $^{6}$He result from neutron-core p-states and the ground and first excited state of $^{11}$Li originate from neutron-core $s^2$ and $sp$-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 $K^-N$ interaction is established as well as the need for a theory for multinucleon absorption of kaons. $K^-$ absorption at rest to specific $\Lambda$ hypernuclei states is briefly discussed.Comment: 6 pages, 3 figures, proceedings of the EXA2011 conference, to appear in Hyperfine Interaction