C. Ratti

Publications (5)2.19 Total impact

• Source

  Available from: ArXiv

  Article: Real and imaginary-time correlators in a thermal medium

  A. Beraudo, J.P. Blaizot, C. Ratti
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  ABSTRACT: We investigate the behavior of a pair of heavy fermions, denoted by Q and , in a hot/dense medium. Although we have in mind the situation where Q and denote heavy quarks, our treatment will be limited to simplified models, which bear only some general similarities with QCD. We study in particular the limiting case where the mass of the heavy fermions is infinite. Then a number of results can be derived exactly: a Schrödinger equation can be established for the correlator of the heavy quarks; the interaction effects exponentiate, leading to a simple instantaneous effective potential for this Schrödinger equation. We consider simple models for the medium in which the pair propagates. In the case where the medium is a plasma of photons and light charged fermions, an imaginary part develops in this effective potential. We discuss the physical interpretation of this imaginary part in terms of the collisions between the heavy particles and the light fermions of the medium; the same collisions also determine the damping rate of the heavy fermions. Finally we study the connection between the real-time propagator of the heavy fermion pair and its Euclidean counterpart, and show that the real part of the potential entering the Schrödinger equation for the real-time propagator is the free energy calculated in the imaginary-time formalism.
  Nuclear Physics A. 01/2008;
• Source

  Available from: arxiv.org

  Article: Mesonic correlation functions at finite temperature and density in the Nambu-Jona-Lasinio model with a Polyakov loop

  H. Hansen, W. M. Alberico, A. Beraudo, A. Molinari, M. Nardi, C. Ratti
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  ABSTRACT: We investigate the properties of scalar and pseudo-scalar mesons at finite temperature and quark chemical potential in the framework of the Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (PNJL model) with the aim of taking into account features of both chiral symmetry breaking and deconfinement. The mesonic correlators are obtained by solving the Schwinger-Dyson equation in the RPA approximation with the Hartree (mean field) quark propagator at finite temperature and density. In the phase of broken chiral symmetry a narrower width for the sigma meson is obtained with respect to the NJL case; on the other hand, the pion still behaves as a Goldstone boson. When chiral symmetry is restored, the pion and sigma spectral functions tend to merge. The Mott temperature for the pion is also computed.
  10/2006;
• Source

  Available from: arxiv.org

  Article: Baryonic masses based on the NJL model

  W.M. Alberico, F. Giacosa, M. Nardi, C. Ratti
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  ABSTRACT: We employ the Nambu-Jona-Lasinio model to determine the vacuum pressure on the quarks in a baryon and hence their density inside. Then we estimate the baryonic masses by implementing the local density approximation for the mean-field quark energies obtained in a uniform and isotropic system. We obtain a fair agreement with the experimental masses.
  European Physical Journal A 01/2003; 16(2):221-228. · 2.19 Impact Factor
• Source

  Available from: arxiv.org

  Article: Stability of strange quark matter: model dependence

  W. M. Alberico, C. Ratti
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  ABSTRACT: The minimum energy per baryon number of strange quark matter is studied, as a function of the strangeness fraction, in the MIT bag model and in two different versions of the Color Dielectric Model: a comparison is made with the hyperon masses having the same strangeness fraction, and coherently calculated within both models. Calculations are carried out in mean field approximation, with one gluon exchange corrections. The results allow to discuss the model dependence of the stability of strangelets: they can be stable in the MIT bag model and in the double minimum version of the Color Dielectric Model, while the single minimum version of the Color Dielectric Model excludes this possibility.
  10/2002;
• Source

  Available from: Alessandro Drago

  Article: Stability of strange quark matter: MIT bag versus Color Dielectric Model

  W. M. Alberico, A. Drago, C. Ratti
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  ABSTRACT: We discuss the properties of strange matter, in particular the minimum of the energy per baryon number as a function of the strangeness fraction. We utilize both the MIT bag model and the Color Dielectric Model and compare the energy per baryon with the masses of hyperons having the corresponding strangeness fraction, which are coherently calculated within both models. We also take into account the perturbative exchange of gluons. The results obtained in the two approaches allow to discuss the stability of strangelets. While the MIT bag model and the double minimum version of the Color Dielectric Model allow the existence of strangelets, the single minimum version of the Color Dielectric Model excludes this possibility.
  10/2001;