Status of the CP-PACS Project

The CP-PACS computer with a peak speed of 300 Gflops was completed in March 1996 and has started to operate. We describe the final specification and the hardware implementation of the CP-PACS computer, and its performance for QCD codes. A plan of the grade-up of the computer scheduled for fall of 1996 is also given.Comment: Talk presented at LATTICE96(machines), 3 pages including 5 PS figure

Toward the Global Structure of Conformal Theories in the SU(3) Gauge Theory

We introduce a new concept "conformal theories with an IR cutoff", after pointing out that the following two categories in SU(3) gauge theories with fundamental N_f fermions possess an IR fixed point: Large N_f QCD with N_f in the conformal window (referred as Conformal QCD) and small N_f QCD with N_f out of the conformal window at temperature T/Tc > 1 (referred as High Temperature QCD). In the conformal theories with an IR cutoff there exists the "conformal region'" together with the confining region and the deconfining region. We verify numerically on a lattice of the size 16^3 x64 the existence of the conformal region and the non-trivial Z(3) structure of the vacuum and the Yukawa-type decay form of meson propagators in the conformal region. We stress that High Temperature QCD is intrinsically accompanied with an IR cutoff. Therefore the understanding the vacuum structure and the property of correlation functions is the key to resolve long standing issues in High Temperature QCD. We further argue that there is a precise correspondence between Conformal QCD and High Temperature QCD in the temporal propagators under the change of the parameters N_f and T/T_c respectively: the one boundary is close to meson states and the other is close to free quark states. In particular, we find the correspondence between Conformal QCD with N_f = 7 and High Temperature QCD with N_f=2 at T ~ 2 Tc being in close relation to a meson unparticle model. From this we estimate the anomalous mass dimension gamma* = 1.2 (1) for N_f=7.Comment: 7 pages, 5 figures, based on the work in collaboration with K. -I Ishikawa, Yu Nakayama and T. Yoshie, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

Computers for Lattice Field Theories

Parallel computers dedicated to lattice field theories are reviewed with emphasis on the three recent projects, the Teraflops project in the US, the CP-PACS project in Japan and the 0.5-Teraflops project in the US. Some new commercial parallel computers are also discussed. Recent development of semiconductor technologies is briefly surveyed in relation to possible approaches toward Teraflops computers.Comment: 15 pages with 16 PS figures, review presented at Lattice 93, LaTeX (espcrc2.sty required

Chiral Phase Transition in Lattice QCD with Wilson Quarks

The nature of the chiral phase transition in lattice QCD is studied for the cases of 2, 3 and 6 flavors with degenerate Wilson quarks, mainly on a lattice with the temporal direction extension $N_t=4$. We find that the chiral phase transition is continuous for the case of 2 flavors, while it is of first order for 3 and 6 flavors.Comment: uuencoded compressed tar file, LaTeX, 14 pages, 7 figure

Quantum chromodynamics with various number of flavors

The phase structure of QCD with various number of flavors is studied for Wilson quarks. For the case of $N_F=3$ we find that the finite temperature deconfining transition is of first order in the chiral limit on an $N_t=4$ lattice. Together with our previous results that the deconfining transition in the chiral limit is continuous for $N_F=2$ and is first order for $N_F=6$, the order of the transition is found to be consistent with a prediction of universality. The case of $SU(2)$ QCD is also studied in the strong coupling limit and the phase structure is found to be quite similar to the case of $SU(3)$: There exists a critical number of flavors $N_F^*$ and for $N_F \geq N_F^*$ the confinement is broken even in the strong coupling limit for light quarks. $N_F^*=3$ corresponding to 7 for $SU(3)$.Comment: 3 pages with 5 PS figures, LaTeX (espcrc2.sty required), UTHEP-26

Scaling of the critical temperature and quark potential with a renormalization group improved SU(3) gauge action

We study the scaling property of the ratio of the critical temperature $T_c$ to the square root of the string tension $\sigma$ in the SU(3) pure gauge theory using a renormalization group improved action. We first determine the critical coupling $\beta_c$ on lattices with temporal extension $N_t=4$ and 6, and then calculate the static quark potential at the critical couplings on lattices at zero temperature. The values of $T_{c}/\sqrt{\sigma}$ in the infinite volume limit are identical within errors, while they are slightly larger than the value extrapolated to the continuum limit with the standard action. We also note that the rotational invariance of the static quark potential is remarkably restored in the both cases, and that the potential $V(R)$ in physical units scales in the whole region of $R$ investigated.Comment: 3 pages of Latex, 5 PostScript figures, Talk presented at LATTICE96(finite temperature

Non-equilibrium and non-linear stationary state in thermoelectric materials

Efficiency of thermoelectric materials is characterized by the figure of merit Z. Z has been believed to be a peculiar material constant. However, the accurate measurements in the present work reveal that Z has large size dependence and a non-linear temperature distribution appears as stationary state in the thermoelectric material. The observation of these phenomena is achieved by the Harman method. This method is the most appropriate way to investigate the thermoelectric properties because the dc and ac resistances are measured by the same electrode configuration. We describe the anomalous thermoelectric properties observed in mainly (Bi,Sb)2Te3 by the Harman method and then insist that Z is not the peculiar material constant but must be defined as the physical quantity dependent of the size and the position in the material.Comment: 9 pages, 4 figures. submitted to Applied Physics Lette