752 research outputs found
Susceptibilities and the Phase Structure of a Chiral Model with Polyakov Loops
In an extension of the Nambu-Jona-Lasinio model where the quarks interact
with the temporal gluon field, represented by the Polyakov loop, we explore the
relation between the deconfinement and chiral phase transitions. The effect of
Polyakov loop dynamics on thermodynamic quantities, on the phase structure at
finite temperature and baryon density and on various susceptibilities is
presented. Particular emphasis is put on the behavior and properties of the
fluctuations of the (approximate) order parameters and their dependence on
temperature and net--quark number density. We also discuss how the phase
structure of the model is influenced by the coupling of the quarks to the
Polyakov loop.Comment: 18 pages, 22 figures; text rearranged and references added. results
and conclusions unchanged; final version accepted for publication in Phys.
Rev.
Effective chiral model with Polyakov loops and its application to hot/dense medium
We study the thermodynamics of the Nambu--Jona-Lasinio model with Polyakov
loops, where spontaneous chiral symmetry breaking and confinement are taken
into account. We focus on the phase structure of the model and explore the
susceptibilities associated with corresponding order parameters under the
mean-field approximation.Comment: 4 pages, 1 figure, to appear in the proceedings of the Yukawa
International Seminars (YKIS) 2006, Nov.27-Dec.1, 2006, Kyoto, Japa
Susceptibilities and the Phase Structure of an Effective Chiral Model with Polyakov Loops
In the Nambu--Jona-Lasinio model with Polyakov loops, we explore the relation
between the deconfinement and chiral phase transitions within the mean-field
approximation. We focus on the phase structure of the model and study the
susceptibilities associated with corresponding order parameters.Comment: 6 pages, 2 figures, contribution to the proceedings of the 19th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(QM2006), November 14-20 2006, Shanghai, Chin
eta-meson photoproduction off protons and deuterons
We present a unitary and gauge-invariant model with coupled channels, which
provides a consistent description of pion photoproduction off nucleons in the
E channel and eta-meson photoproduction off protons and deuterons. An
effective field theory with hadrons and photons is constructed, which includes
non-resonant Born terms as well as the S(1535) and S(1650) baryon
resonances. Due to the coupling between the channels, the production of
eta-mesons is strongly affected by the S(1650) although its direct
coupling to the N channel is negligible. The rho- and omega-meson
exchange terms are important for achieving a consistent description of both
pion- and photon-induced reactions.Comment: 11 pages Latex, 4 Postscript Figure
QCD phase diagram and charge fluctuations
We discuss the phase structure and fluctuations of conserved charges in two
flavor QCD. The importance of the density fluctuations to probe the existence
of the critical end point is summarized. The role of these fluctuations to
identify the first order phase transition in the presence of spinodal phase
separation is also discussed.Comment: 8 pages, 8 figures, plenary talk given at the 19th International
Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2006
(QM 2006), Shanghai, China, 14-20 Nov 200
Density fluctuations and chiral phase transition
Based on an effective QCD Lagrangian we discuss the properties of charge
density fluctuations in the vicinity of chiral phase transition. We explore
thermodynamics in the presence of spinodal phase separation. We show that
appearance of spinodal decomposition in a non-equilibrium first order phase
transition results in divergence of the charge density fluctuations related
with the electric charge and baryon number conservation. Consequently,
divergent fluctuations at the chiral phase transition are not only attributed
to the critical end point but are also there along the first order phase
transition if the spinodal phase separation take place. Based on the mean field
dynamics, the critical exponents for these singular behavior of charge
susceptibilities are also discussed.Comment: 8 pages, 4 figures, contribution to SQM 2007 in Levoca, Slovakia, J.
Phys. G in pres
Topo-Geometric Filtration Scheme for Geometric Active Contours and Level Sets: Application to Cerebrovascular Segmentation
One of the main problems of the existing methods for the
segmentation of cerebral vasculature is the appearance in the segmentation
result of wrong topological artefacts such as the kissing vessels.
In this paper, a new approach for the detection and correction of such
errors is presented. The proposed technique combines robust topological
information given by Persistent Homology with complementary geometrical
information of the vascular tree. The method was evaluated on 20
images depicting cerebral arteries. Detection and correction success rates
were 81.80% and 68.77%, respectively
Density fluctuations in the presence of spinodal instabilities
Density fluctuations resulting from spinodal decomposition in a non-equilibrium first-order chiral phase transition are explored. We show that such instabilities generate divergent fluctuations of conserved charges along the isothermal spinodal lines appearing in the coexistence region. Thus, divergent density fluctuations could be a signal not only for the critical end point but also for the first order phase transition expected in strongly interacting matter. We also show that the mean-field critical exponent at the spinodal lines and at the critical end point are identical. Our analysis is performed in the mean-field approximation to the NJL model formulated at finite temperature and density. However, our main conclusions are expected to be generic and model independent
Charge Fluctuations along the QCD phase boundary
We discuss the properties of the net--quark and isovector fluctuations along the chiral phase transition line in the plane spanned by temperature and baryon chemical potential. Our results are obtained in terms of the Nambu--Jona-Lasinio (NJL) model within the mean-field approximation. The model is formulated at the finite temperature and for non-vanishing net--quark and the isospin chemical potentials. The fermion interactions are controlled by the strength of the scalar and vector couplings in the iso-scalar and iso-vector channels of constituent quarks. We explore properties and differences in the behavior of the net--quark number and isovector susceptibilities for different values of thermal parameters near the phase transition. We argue that any non-monotonic behavior of the net--quark number susceptibility along the phase transition boundary is an excellent probe of the existence and the position of the second order endpoint in the QCD phase diagram
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