S. Hioki

Scaling study of pure gauge lattice QCD by Monte Carlo renormalization group method

The scaling behavior of pure gauge SU(3) in the region [beta]=5.85[minus]7.60 is examined by a Monte Carlo renormalization group analysis. The coupling shifts induced by factor 2 blocking are measured on both 32[sup 4] and 16[sup 4] lattices with high statistics. A systematic deviation from naive 2-loop scaling is clearly seen. The mean field and effective coupling constant schemes explain part, but not all, of the deviation. It can be accounted for by a suitable change of coupling constant, including a correction term [ital O]([ital g][sup 7]) in the 2-loop lattice [beta] function. Based on this improvement, [radical][sigma] /[Lambda][sub M[bar S]][sup [ital n]][sub [ital f]]=0 is estimated to be 2.2[plus minus]0.1 from the analysis of the string tension [sigma].

Gauge-fixing ambiguity and monopole number

Abstract Gauge-fixing ambiguities of lattice SU (2) QCD are studied in the maximally abelian and unitary gauges. In the former, we find local maxima of a gauge-fixing function which may correspond to Gribov copies. There is a definite anti-correlation between the number of monopoles and the value of the function. Errors of measured quantities coming from the ambiguity are found to be less than inherent dispersion in the ensemble average. No ambiguity is found in the unitary gauges.

Search for effective lattice action of pure QCD

We study a coupling flow of pure QCD gauge system by using the Monte Carlo Renormalization Group method. A rough location of the renormalized trajectory in two coupling space is obtained. Also we compare 4 different actions; (a)standard Wilson, (b)Symanziks, (c)Iwasakis and (d)QCDTAROs. The rotational symmetry is restored better as an action gets close to the renormalized trajectory.Abstract We study a coupling flow of pure QCD gauge system by using the Monte Carlo Renormalization Group method. A rough location of the renormalized trajectory in two coupling space is obtained. Also we compare 4 different actions; (a)standard Wilson, (b)Symanziks, (c)Iwasakis and (d)QCDTAROs. The rotational symmetry is restored better as an action gets close to the renormalized trajectory.

Monopole distribution in momentum space in SU(2) lattice gauge theory

Abstract In this paper, the monopole defined in the maximally abelian gauge is investigated by the use of the cooling technique. We find that the scaling behavior of extended monopoles appears after cooling, while it is not seen before cooling. The monopole distribution in momentum space begins to broaden as the temperature increases in the deconfinement phase; this feature is clearer for extended and cooled monopoles.

Screening mass responses to chemical potential at finite temperature

Responses to chemical potential of the pseudoscalar meson screening mass and the chiral condensate in lattice QCD are investigated. On a 16 × 82 × 4 lattice with two flavors of staggered quarks the first and second responses below and above Tc are evaluated. Different behavior in the low and the high temperature phases are observed, which may be explained as a consequence of the chiral symmetry breaking and restoration.

Quantum Chromodynamics Simulation on NWT

A portable QCD simulation program running on NWT with 128 PEs shows the performance 0.032 micro sec/link update, which is about 189 times faster than a highly optimized code on CRAY X-MP/48 with four processors. The performance corresponds to 178 GFLOPS sustained speed.

QCD on the highly parallel computer AP1000

Abstract We have been running quenched QCD simulations on 32 4 and 32 3 × 48 lattices using a 512 processor AP1000, which is a highly parallel computer with up to 1024 processing elements. We have developed programs for update, blocking and hadron propagator calculations. The pseudo heatbath and the overrelaxation algorithms were used for the update with performance of 2.6 and 2.0 μsec/link, respectively.

Autocorrelation in updating pure SU(3) lattice gauge theory by the use of overrelaxed algorithms

Abstract We measure the sweep-to-sweep autocorrelations of blocked loops below and above the deconfinement transition for SU(3) on a 164 lattice using 20000–140000 Monte-Carlo updating sweeps. A divergence of the autocorrelation time toward the critical β is seen at high blocking levels. The peak is near β = 6.33 where we observe 440 ± 210 for the autocorrelation time of 1 × 1 Wilson loop on 24 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 β. Above the critical β, however, no clear difference between these two algorithms can be seen and the system decorrelates rather fast.

Hadron spectroscopy on a 323 × 48 lattice

We report the first results of a hadron spectrum measurement by the QCD_TARO Collaboration with the massively parallel computer AP1000. The main memory of AP1000 is currently 8Gbytes (final goal : 16 Gbytes), which allows us to treat rather large lattices. We measure the quenched Wilson spectrum on a 323 × 48 lattice at β = 6.3. We obtain a good agreement with an empirical curve on the Edinburgh plot.

Topological quantities around critical temperature on an anisotropic lattice

Using an anisotropic lattice, the topological nature of the SU(3) gauge system around the critical temperature is studied. It is observed that the instanton density nQ and the topological susceptibility χt are clearly suppressed in the deconfining phase. Magnetic and static configrations in the deconfinement phase and meron type configuration are also observed. We investigate these quantities in a semi-local way.