1,404 research outputs found
Quarkyonic matter in lattice QCD at strong coupling
We study the phase diagram of quark matter at finite temperature and density
in the strong coupling lattice QCD with one species of unrooted staggered
fermions including finite coupling () effects for color SU(). We
find that we may have partially chiral restored medium density matter at
, which would correspond to the quarkyonic matter suggested at large
.Comment: 9 pages, 4 figure
Another mean field treatment in the strong coupling limit of lattice QCD
We discuss the QCD phase diagram in the strong coupling limit of lattice QCD
by using a new type of mean field coming from the next-to-leading order of the
large dimensional expansion. The QCD phase diagram in the strong coupling limit
recently obtained by using the monomer-dimer-polymer (MDP) algorithm has some
differences in the phase boundary shape from that in the mean field results. As
one of the origin to explain the difference, we consider another type of
auxiliary field, which corresponds to the point-splitting mesonic composite.
Fermion determinant with this mean field under the anti-periodic boundary
condition gives rise to a term which interpolates the effective potentials in
the previously proposed zero and finite temperature mean field treatments.
While the shift of the transition temperature at zero chemical potential is in
the desirable direction and the phase boundary shape is improved, we find that
the effects are too large to be compatible with the MDP simulation results.Comment: Talk given at 28th International Symposium on Lattice Field Theory
(Lattice 2010), Villasimius, Sardinia, Italy, 14-19 June, 201
Chiral and deconfinement transitions in strong coupling lattice QCD with finite coupling and Polyakov loop effects
We investigate chiral and deconfinement transitions in the framework of the
strong coupling lattice QCD for color SU(3) with one species of unrooted
staggered fermion at finite temperature and quark chemical potential. We take
account of the leading order Polyakov loop terms as well as the
next-to-next-to-leading order (1/g^4) fermionic terms of the strong coupling
expansion in the effective action. We investigate the Polyakov loop effects by
comparing two approximation schemes, a Haar measure method (no fluctuation from
the mean field) and a Weiss mean-field method (with fluctuations). The
effective potential is obtained in both cases, and we analytically clarify the
Polyakov loop contributions to the effective potential. The Polyakov loop is
found to suppress the chiral condensate and to reduce the chiral transition
temperature at mu=0, and the chiral transition temperature roughly reproduces
the Monte Carlo results at beta=2N_c/g^2 \lesssim 4. The deconfinement
transition is found to be the crossover and first order for light (am_0
\lesssim 4 at beta=4) and heavy quark masses, respectively.Comment: 13 pages, 15 figures. v2; More dicussions added, figures improved,
and typos correcte
Effective Potential in the Strong-coupling Lattice QCD with Next-to-Next-to-Leading Order Effects
We derive an analytic expression of the effective potential at finite
temperature (T) and chemical potential (mu) in the strong-coupling lattice QCD
for color SU(3) including next-to-next-to-leading order (NNLO) effects in the
strong coupling expansion. NNLO effective action terms are systematically
evaluated in the leading order of the large dimensional (1/d) expansion, and
are found to come from some types of connected two plaquette configurations. We
apply the extended Hubbard-Stratonovich transformation and a gluonic dressed
fermion technique to the effective action, and obtain the effective potential
as a function of T, mu, and two order parameters; chiral condensate and a
vector potential field. The next-to-leading order (NLO) and NNLO effects result
in modifications of the wave function renormalization factor, quark mass and
chemical potential. We find that T_{c,mu=0} and mu_{c,T=0} are similar to the
NLO results, whereas the position of the critical point is sensitive to NNLO
corrections.Comment: 27 pages, 10 figures. v2; More dicussions added, figures improved,
and typos correcte
Phase diagram evolution at finite coupling in strong coupling lattice QCD
We investigate the chiral phase transition in the strong coupling lattice QCD
at finite temperature and density with finite coupling effects. We adopt one
species of staggered fermion, and develop an analytic formulation based on
strong coupling and cluster expansions. We derive the effective potential as a
function of two order parameters, the chiral condensate sigma and the quark
number density , in a self-consistent treatment of the next-to-leading
order (NLO) effective action terms. NLO contributions lead to modifications of
quark mass, chemical potential and the quark wave function renormalization
factor. While the ratio mu_c(T=0)/Tc(mu=0) is too small in the strong coupling
limit, it is found to increase as beta=2Nc/g^2 increases. The critical point is
found to move in the lower T direction as beta increases. Since the vector
interaction induced by is shown to grow as beta, the present trend is
consistent with the results in Nambu-Jona-Lasinio models. The interplay between
two order parameters leads to the existence of partially chiral restored
matter, where effective chemical potential is automatically adjusted to the
quark excitation energy.Comment: 17 pages, 9 figure
Polyakov loop effects on the phase diagram in strong-coupling lattice QCD
We investigate the Polyakov loop effects on the QCD phase diagram by using
the strong-coupling (1/g^2) expansion of the lattice QCD (SC-LQCD) with one
species of unrooted staggered quark, including O}(1/g^4) effects. We take
account of the effects of Polyakov loop fluctuations in Weiss mean-field
approximation (MFA), and compare the results with those in the Haar-measure MFA
(no fluctuation from the mean-field). The Polyakov loops strongly suppress the
chiral transition temperature in the second-order/crossover region at small
chemical potential, while they give a minor modification of the first-order
phase boundary at larger chemical potential. The Polyakov loops also account
for a drastic increase of the interaction measure near the chiral phase
transition. The chiral and Polyakov loop susceptibilities have their peaks
close to each other in the second-order/crossover region. In particular in
Weiss MFA, there is no indication of the separated deconfinement transition
boundary from the chiral phase boundary at any chemical potential. We discuss
the interplay between the chiral and deconfinement dynamics via the bare quark
mass dependence of susceptibilities.Comment: 17 pages, 17 figure
- …