1,221 research outputs found
Chiral phase transition in the vector meson extended linear sigma model
In the framework of an SU(3) (axial)vector meson extended linear sigma model
with additional constituent quarks and Polyakov loops, we investigate the
effects of (axial)vector mesons on the chiral phase transition. The parameters
of the Lagrangian are set at zero temperature and we use a hybrid approach
where in the effective potential the constituent quarks are treated at one-loop
level and all the mesons at tree-level. We have four order parameters, two
scalar condensates and two Polyakov loop variables and their temperature and
baryochemical potential dependence are determined from the corresponding field
equations. We also investigate the changes of the tree-level scalar meson
masses in the hot and dense medium.Comment: 5 pages, 6 figure
Phase statistics of the WMAP 7 year data
We performed a comprehensive statistical analysis using complex phases of the
a_lm coefficients computed from the most recent data of the Wilkinson Microwave
Anisotropy Probe (WMAP). Our aim was to confirm or constrain the presence of
non-Gaussianities in the data. We found phase correlations - that suggest
non-Gaussianity - at high-l in a_lm coefficients by applying various
statistical tests. Most of all, we detected a non-Gaussian signal reaching a
significance of 4.7 sigma using random walk statistics and simulations.
However, our conclusion is that the non-Gaussian behavior is due to
contamination from galactic foregrounds that show up in small scales only. When
masked out the contaminated regions, we found no significant non-Gaussianity.
Furthermore, we constrained the f_NL parameter using CMB simulations that mimic
primordial non-Gaussianity. Our estimate is f_NL=40 +/- 200, in agreement with
previous measurements and inflationary expectations.Comment: 4 pages, 4 figures, Accepted for Publication in A
Existence of the critical endpoint in the vector meson extended linear sigma model
The chiral phase transition of the strongly interacting matter is
investigated at nonzero temperature and baryon chemical potential mu_B within
an extended (2+1) flavor Polyakov constituent quark-meson model which
incorporates the effect of the vector and axial vector mesons. The effect of
the fermionic vacuum and thermal fluctuations computed from the grand potential
of the model is taken into account in the curvature masses of the scalar and
pseudoscalar mesons. The parameters of the model are determined by comparing
masses and tree-level decay widths with experimental values in a
chi^2-minimization procedure which selects between various possible assignments
of scalar nonet states to physical particles. We examine the restoration of the
chiral symmetry by monitoring the temperature evolution of condensates and the
chiral partners' masses and of the mixing angles for the pseudoscalar eta-eta'
and the corresponding scalar complex. We calculate the pressure and various
thermodynamical observables derived from it and compare them to the continuum
extrapolated lattice results of the Wuppertal-Budapest collaboration. We study
the T-mu_B phase diagram of the model and find that a critical end point exists
for parameters of the model, which give acceptable values of chi^2.Comment: 21 pages, 8 color eps figures, published versio
Monopoles and instantons in SU(2) lattice gauge theory
We investigate the monopole-instanton correlation in SU(2) lattice gauge
theory using a renormalisation group inspired smoothing technique. We look at
the properties of monopole clusters and their correlation with instantons.
Since the action of the smoothed configurations is dominated by instantons we
compare the smoothed Monte Carlo lattices to artificially reconstructed
configurations with the same instanton content but no other fluctuations. Both
parallel and randomly rotated (in group space) instanton ensembles are
considered.Comment: LATTICE98(confine
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