9,517 research outputs found

### 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

### 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

### QCD Phase Transition with Strange Quark in Wilson Formalism for Fermions

The nature of QCD phase transition is studied with massless up and down
quarks and a light strange quark, using the Wilson formalism for quarks on a
lattice with the temporal direction extension $N_t=4$. We find that the phase
transition is first order in the cases of both about 150 MeV and 400 MeV for
the strange quark mass. These results together with those for three degenerate
quarks suggest that QCD phase transition in nature is first order.Comment: uuencoded compressed tar file, LaTeX, 13 pages, 9 figures, Minor
errors for quoting references are corrected and a reference is adde

### Phase Diagram of QCD at Finite Temperatures with Wilson Fermions

Phase diagram of QCD with Wilson fermions for various numbers of flavors
$N_F$ is discussed. Our simulations mainly performed on a lattice with the
temporal size $N_t =4$ indicate the following: The chiral phase transition is
of first order when $3 \le N_F \le 6$, while it is continuous when $N_F=2$. For
the realistic case of massless u and d quarks and the strange quark with $m_q =
150$ MeV, the phase transition is first order. The sharp transition in the
intermediate mass region for $N_F=2$ at $N_t=4$ observed by the MILC group
disappears when an RG improvement is made for the pure gauge action.Comment: ps file, 7 pages with 5 figures, contribution to Lattice 94

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