815 research outputs found

    Finite-Size Effects on Nucleation in a First-Order Phase Transition

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    We discuss finite-size effects on homogeneous nucleation in first-order phase transitions. We study their implications for cosmological phase transitions and to the hadronization of a quark-gluon plasma generated in high-energy heavy ion collisions. Very general arguments allow us to show that the finite size of the early universe has virtually no relevance in the process of nucleation and in the growth of cosmological bubbles during the primordial quark-hadron and the electroweak phase transitions. In the case of high-energy heavy ion collisions, finite-size effects play an important role in the late-stage growth of hadronic bubbles.Comment: 6 pages, no figures, 1 reference adde

    Fermion mass and the pressure of dense matter

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    We consider a simple toy model to study the effects of finite fermion masses on the pressure of cold and dense matter, with possible applications in the physics of condensates in the core of neutron stars and color superconductivity.Comment: 3 pages, 2 figures. Presented at Quark Confinement and the Hadron Spectrum 7, Ponta Delgada, Azores, Portugal, 2-7 Sep 200

    Nucleation in the chiral transition with an inhomogeneous background

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    We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. Modifications in the effective potential and their consequences for the bubble nucleation process are discussed.Comment: 4 pages, 4 figures. To appear in the proceedings of I Latin American Workshop on High Energy Phenomenology (LAWHEP 2005), Porto Alegre, Brazil, 1-3 Dec 200

    Transient photon production in a QGP

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    We discuss the shortcomings of a formula that has been used in the literature to compute the number of photons emitted by a hot or dense system during a finite time, and show that the transient effects it predicts for the photon rate are unphysical.Comment: 4 pages, to appear in the proceedings of Hadron Physics - RANP 2004, Angra dos Reis, Brazi

    Chiral pions in a magnetic background

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    We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the π−\pi^{-}, interestingly, this happens solely due to the trivial Landau quantization shift ∼∣eB∣\sim |eB|, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by ∼10\sim 10% for a magnetic field ∣eB∣∼mπ2|eB|\sim m_\pi^2, which favors pion condensation at high density and low temperatures.Comment: 7 pages, 5 figure
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