Systematic study of autocorrelation time in pure SU(3) lattice gauge theory

Results of our autocorrelation measurement performed on Fujitsu AP1000 are reported. We analyze (i) typical autocorrelation time, (ii) optimal mixing ratio between overrelaxation and pseudo-heatbath and (iii) critical behavior of autocorrelation time around cross-over region with high statistic in wide range of $\beta$ for pure SU(3) lattice gauge theory on $8^4$, $16^4$ and $32^4$ lattices. For the mixing ratio K, small value (3-7) looks optimal in the confined region, and reduces the integrated autocorrelation time by a factor 2-4 compared to the pseudo-heatbath. On the other hand in the deconfined phase, correlation times are short, and overrelaxation does not seem to matter For a fixed value of K(=9 in this paper), the dynamical exponent of overrelaxation is consistent with 2 Autocorrelation measurement of the topological charge on $32^3 \times 64$ lattice at $\beta$ = 6.0 is also briefly mentioned.Comment: 3 pages of A4 format including 7-figure

Autocorrelation in Updating Pure SU(3) Lattice Gauge Theory by the use of Overrelaxed Algorithms

We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement transition for SU(3) on a $16^4$ lattice using 20000-140000 Monte-Carlo updating sweeps. A divergence of the autocorrelation time toward the critical $\beta$ is seen at high blocking levels. The peak is near $\beta$ = 6.33 where we observe 440 $\pm$ 210 for the autocorrelation time of $1\times 1$ Wilson loop on $2^4$ blocked lattice. The mixing of 7 Brown-Woch overrelaxation steps followed by one pseudo-heat-bath step appears optimal to reduce the autocorrelation time below the critical $\beta$. Above the critical $\beta$, however, no clear difference between these two algorithms can be seen and the system decorrelates rather fast.Comment: 4 pages of A4 format including 6-figure

Renormalization Group Flow of SU(3) Gauge Theory

We calculate numerically the renormalization group (RG) flow of lattice QCD in two-coupling space, $(\beta_{1\times 1},\beta_{1\times 2})$. This is the first explicit calculation of the RG flow of SU(3) gauge theory. From the RG flow,a renormalized trajectory (RT) is revealed. Its behavior is consistent with the strong coupling expansion near the high-temperature fixed point. Actions with $(\beta_{1\times 1},\beta_{1\times 2})$ are studied; the lattice spacing is evaluated by measuring the string tension from the heavy quark potential. Recovery of the rotational symmetry is studied as a function of the ratio $\beta_{1\times 2} / \beta_{1\times 1}$

Summing up the perturbation series in the Schwinger Model

Perturbation series for the electron propagator in the Schwinger Model is summed up in a direct way by adding contributions coming from individual Feynman diagrams. The calculation shows the complete agreement between nonperturbative and perturbative approaches.Comment: 10 pages (in REVTEX

Fermions in three-dimensional spinfoam quantum gravity

We study the coupling of massive fermions to the quantum mechanical dynamics of spacetime emerging from the spinfoam approach in three dimensions. We first recall the classical theory before constructing a spinfoam model of quantum gravity coupled to spinors. The technique used is based on a finite expansion in inverse fermion masses leading to the computation of the vacuum to vacuum transition amplitude of the theory. The path integral is derived as a sum over closed fermionic loops wrapping around the spinfoam. The effects of quantum torsion are realised as a modification of the intertwining operators assigned to the edges of the two-complex, in accordance with loop quantum gravity. The creation of non-trivial curvature is modelled by a modification of the pure gravity vertex amplitudes. The appendix contains a review of the geometrical and algebraic structures underlying the classical coupling of fermions to three dimensional gravity.Comment: 40 pages, 3 figures, version accepted for publication in GER

DETERMINATION OF SCALE PARAMETERS ON ANISOTROPIC LATTICES

Karsch F, Burgers G, Nakamura A, Stamatescu IO. DETERMINATION OF SCALE PARAMETERS ON ANISOTROPIC LATTICES. 1987

The SU(3) deconfinement phase transition in the presence of quarks

Hasenfratz P, Karsch F, Stamatescu IO. The SU(3) deconfinement phase transition in the presence of quarks. Physics Letters, B. 1983;133(3-4):221-226.The fate of the deconfinement phase transition is studied as a function of the quark mass on a 8 3 × 2 lattice. The first order phase transition present in the pure SU(3) lattice gauge theory weakens rapidly as the quark mass is decreased and no such transition is observed below a critical mass value. This critical mass appears to be large, of the order of GeV

QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter

Karsch F, Stamatescu IO. QCD thermodynamics with light quarks. Quantum corrections to the fermionic anisotropy parameter. Physics Letters, B. 1989;227(1):153-160.We determine the O(g 2) corrections to the anisotropy parameter in the fermionic action, which are required to guarantee a rotational invariant continuum limit on anisotropic lattices. We show the importance of these quantum corrections for QCD thermodynamics on isotropic lattices. Only after including these corrections do we find, on large lattices, agreement between lattice and continuum perturbation theory at finite temperature. The implied renormalization of the operators used in Monte Carlo simulations to measure the energy density leads to a 20% reduction of the fermionic part of the energy density which, to a large extent, compensates the previously found overshooting in the gluonic sector. We reanalyze existing Monte Carlo data for the thermodynamics of QCD with light quarks and extract the entropy density. We find that immediately above the chiral transition the entropy density is already close to the ideal gas value

Wilson fermions and the topological charge on the lattice

Karsch F, Seiler E, Stamatescu IO. Wilson fermions and the topological charge on the lattice. Nuclear Physics, B. 1986;271(2):349-368.We investigate the realization on the lattice of the relation between the chiral properties of the fermions and the topological properties of the gauge field. A lattice definition of the topological charge density via the U(1) Adler-Bardeen anomaly is analysed with the help of given configurations of nontrivial topology and for 2-dimensional quenched QED