L. L. Salcedo

Publications (35)9.56 Total impact

• Article: Excited Hadrons, Heavy Quarks and QCD thermodynamics

  E. Ruiz Arriola, L. L. Salcedo, E. Megias
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  ABSTRACT: We show how excited states in QCD can be profitably used to build up the Polyakov loop in the fundamental representation at finite tempera- tures below the phase transition. The conditions under which a Hagedorn temperature for the Polyakov loop can be defined are analyzed.
  04/2013;
• Article: Polyakov loop and the hadron resonance gas model.

  E Megías, E Ruiz Arriola, L L Salcedo
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  ABSTRACT: The Polyakov loop has been used repeatedly as an order parameter in the deconfinement phase transition in QCD. We argue that, in the confined phase, its expectation value can be represented in terms of hadronic states, similarly to the hadron resonance gas model for the pressure. Specifically, L(T)≈1/2[under ∑]αg_{α}e^{-Δ_{α}/T}, where g_{α} are the degeneracies and Δ_{α} are the masses of hadrons with exactly one heavy quark (the mass of the heavy quark itself being subtracted). We show that this approximate sum rule gives a fair description of available lattice data with N_{f}=2+1 for temperatures in the range 150  MeV<T<190  MeV with conventional meson and baryon states from two different models. For temperatures below 150 MeV different lattice results disagree. One set of data can be described if exotic hadrons are present in the QCD spectrum while other sets do not require such states.
  Physical Review Letters 10/2012; 109(15):151601. · 7.37 Impact Factor
• Article: From Chiral quark dynamics with Polyakov loop to the hadron resonance gas model

  E. Ruiz Arriola, E. Megias, L. L. Salcedo
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  ABSTRACT: Chiral quark models with Polyakov loop at finite temperature have been often used to describe the phase transition. We show how the transition to a hadron resonance gas is realized based on the quantum and local nature of the Polyakov loop.
  07/2012;
• Source

  Available from: ArXiv

  Article: Correlations between perturbation theory and power corrections in QCD at zero and finite temperature

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The duality between QCD perturbative series and power corrections recently conjectured by Narison and Zakharov is analyzed. We propose to study correlations between both contributions as diagnostics tool. A very strong correlation between perturbative and non perturbative contributions is observed for several observables at zero and at finite temperature supporting the validity of the dual description. Comment: 7 pages, 5 figures, 7 tables
  12/2009;
• Source

  Available from: ArXiv

  Article: Trace Anomaly, Thermal Power Corrections and Dimension Two condensates in the deconfined phase

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The trace anomaly of gluodynamics on the lattice shows clear fingerprints of a dimension two condensate above the phase transition. The condensate manifests itself through even powers of the inverse temperature while the total perturbative contribution corresponds to a mild temperature dependence and turns out to be compatible with zero within errors. We try several resummation methods based on a renormalization group improvement. The trace anomaly data are analyzed and compared with other determinations of the dimension two condensate based on the Polyakov loop and the heavy qq free energy, yielding roughly similar numerical values. The role of glueballs near the transition is also discussed. Comment: 15 pages, 7 figures
  03/2009;
• Source

  Available from: ArXiv

  Article: The Powers of Deconfinement

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The trace anomaly of gluodynamics encodes the breakdown of classical scale invariance due to interactions around the deconfinement phase transition. While it is expected that at high temperatures perturbation theory becomes applicable we show that current lattice calculations are far from the perturbative regime and are dominated instead by inverse even power corrections in the temperature, while the total perturbative contribution is estimated to be extremely small and compatible with zero within error bars. We provide an interpretation in terms of dimension-two gluon condensate of the dimensionally reduced theory which value agrees with a similar analysis of power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD.
  10/2008;
• Source

  Available from: ArXiv

  Article: Trace Anomaly and dimension two gluon condensate above the phase transition

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The dimension two gluon condensate has been used previously within a simple phenomenological model to describe power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD (hep-ph/0505215,hep-ph/0702055). The QCD trace anomaly of gluodynamics also shows unequivocal inverse temperature power corrections which may be encoded as dimension two gluon condensate. We analyze lattice data of the trace anomaly and compare with other determinations of the condensate from previous references, yielding roughly similar numerical values.
  05/2008;
• Source

  Available from: ugr.es

  Article: Power corrections in the quark-antiquark potential at finite temperature

  E Megías, E Ruiz Arriola, L L Salcedo
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  ABSTRACT: A recently proposed phenomenological model, which includes nonperturbative effects from dimension two gluon condensates, is applied to analyze the available lattice data for the heavy quark free energy in the deconfined phase of quenched QCD. For large q q separations, we recover previous results for the Polyakov loop, exhibiting unequivocal power corrections in the temperature. For the q q potential at finite temperature and finite separation, we find that a good overall description of the lattice data can be achieved once the condensate is properly accounted for. In addition, the model predicts a duality between the zero temperature potential as a function of the q q separation, on the one hand, and the quark self-energy as a function of the temperature, on the other, which turns out to be satisfied to a high degree by the lattice data.
  03/2007;
• Source

  Available from: arxiv.org

  Article: The quark-antiquark potential at finite temperature and the dimension two gluon condensate

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: A recently proposed phenomenological model, which includes non perturbative effects from dimension two gluon condensates, is applied to analyze the available lattice data for the heavy quark free energy in the deconfined phase of quenched QCD. For large $q\bar{q}$ separations we recover previous results for the Polyakov loop, exhibiting unequivocal condensate contributions. For the $q\bar{q}$ potential at finite temperature and finite separation we find that a good overall description of the lattice data can be achieved once the condensate is properly accounted for. In addition, the model predicts a duality between the zero temperature potential as a function of the $q\bar{q}$ separation, on the one hand, and the quark selfenergy as a function of the temperature, on the other, which turns out to be satisfied to a high degree by the lattice data.
  03/2007;
• Source

  Available from: arxiv.org

  Article: Dimension-2 condensates and Polyakov Chiral Quark Models

  E. Megıas, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end, we use a center symmetry-breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics data above the phase transition in terms of dimension-2 gluon condensate. The role played by the quantum and local nature of the Polyakov loop is emphasized.
  European Physical Journal A 02/2007; 31(4):553-556. · 2.19 Impact Factor
• Source

  Available from: ArXiv

  Article: Dimension 2 condensates and Polyakov Chiral Quark Models

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end we use a center symmetry breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics data above the phase transition in terms of dimension 2 gluon condensate. The role played by the quantum and local nature of the Polyakov loop is emphasized.
  11/2006;
• Source

  Available from: arxiv.org

  Article: The Quantum and Local Polyakov loop in Chiral Quark Models at Finite Temperature

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We describe results for the confinement-deconfinement phase transition as predicted by the Nambu--Jona-Lasinio model where the local and quantum Polyakov loop is coupled to the constituent quarks in a minimal way (PNJL). We observe that the leading correlation of two Polyakov loops describes the chiral transition accurately. The effects of the current quark mass on the transition are also analysed.
  11/2006;
• Source

  Available from: arxiv.org

  Article: Chiral Lagrangian at finite temperature from the Polyakov-Chiral Quark Model

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We analyze the consequences of the inclusion of the gluonic Polyakov loop in chiral quark models at finite temperature. Specifically, the low-energy effective chiral Lagrangian from two such quark models is computed. The tree level vacuum energy density, quark condensate, pion decay constant and Gasser-Leutwyler coefficients are found to acquire a temperature dependence. This dependence is, however, exponentially small for temperatures below the mass gap in the full unquenched calculation. The introduction of the Polyakov loop and its quantum fluctuations is essential to achieve this result and also the correct large $N_c$ counting for the thermal corrections. We find that new coefficients are introduced at ${\cal O}(p^4)$ to account for the Lorentz breaking at finite temperature. As a byproduct, we obtain the effective Lagrangian which describes the coupling of the Polyakov loop to the Goldstone bosons.
  08/2006;
• Source

  Available from: arxiv.org

  Article: Polyakov loop at low and high temperatures

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We describe how the coupling of the gluonic Polyakov loop to quarks solves different inconsistencies in the standard treatment of chiral quark models at finite temperature at the one quark loop level. Large gauge invariance is incorporated and an effective theory of quarks and Polyakov loops as basic degrees of freedom is generated. From this analysis we find a strong suppression of finite temperature effects in hadronic observables below the deconfinement phase transition triggered by approximate triality conservation in a phase where chiral symmetry is spontaneously broken (Polyakov cooling). We also propose a simple phenomenological model to describe the available lattice data for the renormalized Polyakov loop in the deconfinement phase. Our analysis shows that non perturbative contributions driven by dimension-2 gluon condensates dominate the behaviour of the Polyakov loop in the regime T_c < T < 6T_c.
  12/2005;
• Source

  Available from: ArXiv

  Article: Non-perturbative contribution to the Polyakov loop above the deconfinement phase transition

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The Polyakov loop is an order parameter to the confinement-deconfinement phase transition in pure gluodynamics. Recently a simple phenomenological model has been proposed to describe the available lattice data for the renormalized Polyakov loop in the deconfinement phase (hep-ph/0505215). These data exhibit unequivocal inverse power temperature corrections driven by a dimension two gluon condensate. The heavy quark free energy is also studied and compared to lattice data.
  11/2005;
• Source

  Available from: ArXiv

  Article: Dimension two condensates and the Polyakov loop above the deconfinement phase transition

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We show that recent available lattice data for the renormalized Polyakov loop above the deconfinement phase transition exhibit unequivocal inverse power temperature corrections driven by a dimension 2 gluon condensate. This simple ansatz provides a good overall description of the data throughout the deconfinement phase until near the critical temperature with just two parameters. One of the parameters is consistent with perturbation theory while a second, non perturbative, parameter provides a numerical value of the condensate which is close to existing zero and finite temperature determinations.
  06/2005;
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  Available from: ArXiv

  Article: The Energy Momentum Tensor of Chiral Quark Models at Low Energies

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: The low energy structure of the energy momentum tensor in several chiral quark models with SU(3) flavor symmetry is analyzed in the presence of external gravitational fields. To this end a derivative expansion in a curved four dimensional space time is considered. This allows us to compute the chiral coefficients $L_{11}$, $L_{12}$, and $L_{13}$, appearing when the model is coupled to gravity and related to space-time curvature properties. Comment: 12 pages. References added. To appear in Physical Review D
  04/2005;
• Source

  Available from: arxiv.org

  Article: Polyakov loop in chiral quark models at finite temperature

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: We describe how the inclusion of the gluonic Polyakov loop incorporates large gauge invariance and drastically modifies finite temperature calculations in chiral quark models after color neutral states are singled out. This generates an effective theory of quarks and Polyakov loops as basic degrees of freedom. We find a strong suppression of finite temperature effects in hadronic observables triggered by approximate triality conservation (Polyakov cooling), so that while the center symmetry breaking is exponentially small with the constituent quark mass, chiral symmetry restoration is exponentially small with the pion mass. To illustrate the point we compute some low energy observables at finite temperature and show that the finite temperature corrections to the low energy coefficients are $N_c$ suppressed due to color average of the Polyakov loop. Our analysis also shows how the phenomenology of chiral quark models at finite temperature can be made compatible with the expectations of chiral perturbation theory. The implications for the simultaneous center symmetry breaking-chiral symmetry restoration phase transition are also discussed. Comment: 24 pages, 8 ps figures. Figure and appendix added. To appear in Physical Review D
  12/2004;
• Source

  Available from: arxiv.org

  Article: Chiral Lagrangians at finite temperature and the Polyakov Loop

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: Heat kernel expansions at finite temperature of massless QCD and chiral quark models generate effective actions relevant for both low and high temperature QCD. The key relevance of the Polyakov Loop to maintain the large and non-perturbative gauge invariance at finite temperature is stressed. Comment: Talk given at 6th Conference on Quark Confinement and the Hadron Spectrum, Villasimius, Sardinia, Italy, 21-25 Sep 2004
  11/2004;
• Source

  Available from: arxiv.org

  Article: Polyakov Loop at Finite Temperature in Chiral Quark Models

  E. Megias, E. Ruiz Arriola, L. L. Salcedo
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  ABSTRACT: At finite temperature, chiral quark models do not incorporate large gauge invariance which implies genuinely non-perturbative finite temperature gluonic degrees of freedom. Motivated by this observation, we describe how the coupling of the Polyakov loop as an independent degree of freedom to quarks not only accounts for large gauge invariance, but also allows to establish in a dynamical way the interaction between composite hadronic states such as Goldstone bosons to finite temperature non-perturbative gluons in a medium which can undergo a confinement-deconfinement phase transition.
  11/2004;