Lattice QCD at non-vanishing density: phase diagram, equation of state

We propose a method to study lattice QCD at non-vanishing temperature (T) and chemical potential (\mu). We use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. The critical endpoint (E) of QCD on the Re(\mu)-T plane is located. We calculate the pressure (p), the energy density (\epsilon) and the baryon density (n_B) of QCD at non-vanishing T and \mu.Comment: Contributed to Workshop on Strong and Electroweak Matter (SEWM 2002), Heidelberg, Germany, 2-5 Oct 200

The QCD equation of state at finite T/\mu on the lattice

We present N_t=4 lattice results for the equation of state of 2+1 flavour staggered, dynamical QCD at finite temperature and chemical potential. We use the overlap improving multi-parameter reweighting technique to extend the equation of state for non-vanishing chemical potentials. The results are obtained along the line of constant physics. Our physical parameters extend in temperature and baryon chemical potential upto \approx 500-600 MeV.Comment: 13 pages 9 figures, talk given at Finite Density QCD at Nara, Nara, Japan, 10-12 July 200

Topology with Dynamical Overlap Fermions

We perform dynamical QCD simulations with $n_f=2$ overlap fermions by hybrid Monte-Carlo method on $6^4$ to $8^3\times 16$ lattices. We study the problem of topological sector changing. A new method is proposed which works without topological sector changes. We use this new method to determine the topological susceptibility at various quark masses.Comment: 15 pages, 3 figure

Relation to intramuscular connective tissue properties to CT-values in longissimus thoracis muscle of Hungarian simmental cattle

Intramuscular connective tissue plays an important role in determining meat tenderness. The objective of the research was to compare the collagen/hydroxyproline content and X-ray Computed Tomographic (CT) connective tissue proportion of longissimus thoracis (LT) muscle in Hungarian Simmental bulls and cows. Animals (n=24) were slaughtered at similar live weight (bulls: 530.6+44.7 kg, cows: 527.3+53.5 kg) under standard commercial conditions in Hungary. After 24 h chilling, LT samples were taken from the right half carcass at the 12th rib. CT examinations were carried out with a 16-slice CT system (slice thickness: 5 mm). Samples were scanned at different user-selectable tube voltages e.g. low: 80 kV and high: 140 kV. CT value at LT muscle area of each mixed scan (80 and 140 kV) was determined. Volumetric connective tissue content was measured (above 200 CT value) as well. Following CT, the hydroxyproline/collagen content and intramuscular fat content of LT were determined. Cows had lower carcass weight (247 kg vs 295 kg), EU conformation score (3.5 vs 5.5), and fatness score (4.2 vs 5.9) than bulls (P<0.01). Bulls had higher LT area, but intramuscular fat content was similar for bulls (2.8±1.9) and cows (2.7±2.0). On the other hand, bulls had lower CT intramuscular connective tissue proportion in LT compared to cows (0.4±0.2% vs 0.7±0.3% P<0.01). The same tendency could be observed for the collagen content (0.5±0.2% vs 0.7±0.1% P<0.01). Correlation between the CT connective tissue proportion of LT and collagen content was r=0.8 (P=0.000). There was a weak positive correlation between slaughter age and CT connective tissue as well as collagen content of LT (r=0.3–0.4, P<0.05). In conclusion, intramuscular connective tissue proportion in LT increased with slaughter age, and older cows had higher collagen and connective tissue proportion than bulls. Mixed CT scans can be used for the analysis of intramuscular connective tissue content

The Effective Particle-Hole Interaction and the Optical Response of Simple Metal Clusters

Following Sham and Rice [L. J. Sham, T. M. Rice, Phys. Rev. 144 (1966) 708] the correlated motion of particle-hole pairs is studied, starting from the general two-particle Greens function. In this way we derive a matrix equation for eigenvalues and wave functions, respectively, of the general type of collective excitation of a N-particle system. The interplay between excitons and plasmons is fully described by this new set of equations. As a by-product we obtain - at least a-posteriori - a justification for the use of the TDLDA for simple-metal clusters.Comment: RevTeX, 15 pages, 5 figures in uufiles format, 1 figure avaible from [email protected]

Diagrammatic Quantum Monte Carlo for Two-Body Problem: Exciton

We present a novel method for precise numerical solution of the irreducible two-body problem and apply it to excitons in solids. The approach is based on the Monte Carlo simulation of the two-body Green function specified by Feynman's diagrammatic expansion. Our method does not rely on the specific form of the electron and hole dispersion laws and is valid for any attractive electron-hole potential. We establish limits of validity of the Wannier (large radius) and Frenkel (small radius) approximations, present accurate data for the intermediate radius excitons, and give evidence for the charge transfer nature of the monopolar exciton in mixed valence materials.Comment: 4 pages, 5 figure

Structural Instability in Polyacene : A Projector Quantum Monte Carlo Study

We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls' instability in a system marginally away from one-dimension. We employ the projector quantum Monte Carlo method to obtain ground state estimates of the energy and various correlation functions. We find strong similarities between polyacene and polyacetylene which can be rationalized from the real-space valence-bond arguments of Mazumdar and Dixit. Electron correlations tend to enhance the Peierls' instability in polyacene. This enhancement appears to attain a maximum at $U/t \sim 3.0$ and the maximum shifts to larger values when the alternation parameter is increased. The system shows no tendency to destroy the imposed bond-alternation pattern, as evidenced by the bond-bond correlations. The cis- distortion is seen to be favoured over the trans- distortion. The spin-spin correlations show that undistorted polyacene is susceptible to a SDW distortion for large interaction strength. The charge-charge correlations indicate the absence of a CDW distortion for the parameters studied.Comment: 13 pages, 10 figures available on reques

Light Hadron Masses from Lattice QCD

This article reviews lattice QCD results for the light hadron spectrum. We give an overview of different formulations of lattice QCD, with discussions on the fermion doubling problem and improvement programs. We summarize recent developments in algorithms and analysis techniques, that render calculations with light, dynamical quarks feasible on present day computer resources. Finally, we summarize spectrum results for ground state hadrons and resonances using various actions.Comment: 53 pages, 24 figures, one table; Rev.Mod.Phys. (published version); v2: corrected typ