3,493 research outputs found
FINITE TEMPERATURE PHASE TRANSITION IN QCD WITH STRANGE QUARK: STUDY WITH WILSON FERMIONS ON THE LATTICE
The effect of the strange quark in the finite temperature phase transition of
QCD is studied on the lattice. Using the one-plaquette gauge action and the
Wilson quark action, the transition in the chiral limit is shown to be
continuous for the case of degenerate two flavors, , while it is of
first order for . For a more realistic case of massless up and down
quarks and a light strange quark, , clear two state signals are
observed both for and 400 MeV. In contrast to a previous
result with staggered quarks, this suggests a first order transition in the
real world. In order to see the implication of these results to the continuum
limit, we started to study these issues using improved actions. First results
using a RG improved gauge action combined with the standard Wilson quark is
presented for the case of : With this action the finite temperature
transition is shown to be continuous in the chiral limit confirming the result
of the standard action. Furthermore, not like the case of the standard action
where lattice artifacts make the transition once very strong at intermediate
values of the hopping parameter on and 6 lattices, a smooth
crossover is found for the improved action when we increase , in
accord with a naive expectation about the fate of second order chiral
transition at finite .Comment: uuencoded compressed PS file, 9 pages, 10 figures, Talk given at the
International Conference {\it Confinement95}, RCNP, Osaka, March 22-24, 199
An Introduction to Finite Temperature Quantum Chromodynamics on the Lattice
In these lectures, we introduce finite temperature QCD on the lattice to
non-experts of the subject. We first formulate lattice QCD both at zero and
finite temperatures. Then a section is devoted to the topic of improved lattice
actions which are becoming an essential ingredient of precision studies of QCD
on the lattice. We then discuss about finite temperature SU(3) gauge theory,
i.e. QCD without dynamical quarks (quenched QCD). Finally, we report recent
status of studies in full QCD taking into account the effects of dynamical
quarks.Comment: Lectures presented at the 1997 Yukawa International Seminar (YKIS'97)
on ``Non-Perturbative QCD --- Structure of the QCD Vacuum ---'', YITP, Kyoto,
Japan, 2--12 Dec. 1997. To be published in the proceedings [Prog. Theor.
Phys. Suppl.
Deconfining chiral transition in QCD on the lattice
The deconfining chiral transition in finite-temperature QCD is studied on the lattice using Wilson quarks. After discussing the nature of chiral limit with Wilson quarks, we first study the case of two degenerate quarks N_F=2, and find that the transition is smooth in the chiral limit on both N_t=4 and 6 lattices. For N_F=3, on the other hand, clear two state signals are observed for m_q \simm{<} 140 MeV on \nt=4 lattices. For a more realistic case of N_F=2+1, i.e.\ two degenerate u and d-quarks and a heavier s-quark, we study the cases m_s \simeq 150 and 400 MeV with m_u = m_d \simeq 0: In contrast to a previous result with staggered quarks, clear two state signals are observed for both cases, suggesting a first order QCD phase transition in the real world
Towards the QCD equation of state at the physical point using Wilson fermion
We study the (2+1)-flavor QCD at nonzero temperatures using nonperturbatively
improved Wilson quarks of the physical masses by the fixed scale approach. We
perform physical point simulations at finite temperatures with the coupling
parameters which were adopted by the PACS-CS Collaboration in their studies
using the reweighting technique. Zero temperature values are obtained on the
PACS-CS configurations which are open to the public on the ILDG/JLDG. Finite
temperature configurations are generated with the RHMC algorithm. The lattice
sizes are with , 13, , 4 which correspond to
--550 MeV. We present results of some basic observables at these
temperatures and the status of our calculation of the equation of state.Comment: 7 pages, 3 figures, proceedings of the 33rd International Symposium
on Lattice Field Theory, July 14-18, 2015, Kobe, Japa
Quantum Chromodynamics with Many Flavors
We investigate the phase structure of lattice QCD for general number of
flavors . Based on numerical data combined with the results of the
perturbation theory we propose the following picture: When , there
is only one IR fixed point at vanishing gauge coupling, i.e., the theory in the
continuum limit is trivial. On the other hand, when , there
is a non-trivial fixed point. Therefore, the theory is non-trivial with
anomalous dimensions, however, without quark confinement. Theories which
satisfy both quark confinement and spontaneous chiral symmetry breaking in the
continuum limit exist only for .Comment: Talk presented by K. Kanaya at the 1997 Yukawa International Seminar
(YKIS'97) on ``Non-Perturbative QCD --- Structure of the QCD Vacuum ---'',
YITP, Kyoto, Japan, 2--12 Dec. 1997. To be published in the proceedings
[Prog. Theor. Phys. Suppl.
Equation of state in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach
We study the equation of state in 2+1 flavor QCD with nonperturbatively
improved Wilson quarks coupled with the RG-improved Iwasaki glue. We apply the
-integration method to nonperturbatively calculate the equation of state by
the fixed-scale approach. With the fixed-scale approach, we can purely vary the
temperature on a line of constant physics without changing the system size and
renormalization constants. Unlike the conventional fixed- approach, it is
easy to keep scaling violations small at low temperature in the fixed scale
approach. We study 2+1 flavor QCD at light quark mass corresponding to
, while the strange quark mass is chosen around the
physical point. Although the light quark masses are heavier than the physical
values yet, our equation of state is roughly consistent with recent results
with highly improved staggered quarks at large .Comment: 14 pages, 12 figures, v2: Table I and Figure 3 are corrected,
reference updated. Main discussions and conclusions are unchanged, v3:
version to appear in PRD, v4: reference adde
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