Publications (47)2.15 Total impact
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Article: Two-flavor QCD at finite quark or isospin density
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ABSTRACT: We exploit analytic continuation to prolongate to the region of real chemical potentials the (pseudo)critical lines of QCD with two degenerate staggered fermions at nonzero temperature and quark or isospin density obtained in the region of imaginary chemical potentials. We determine the curvatures at zero chemical potential and quantify the deviation between the cases of finite quark and of finite isospin chemical potential. In both circumstances deviations from a quadratic dependence of the pseudocritical lines on the chemical potential are clearly seen. We try different extrapolations and, for the nonzero isospin chemical potential, confront them with the results of direct Monte Carlo simulations. We also find that, as for the finite quark chemical potential, an imaginary isospin chemical potential can strengthen the transition till turning it into strong first order.10/2012; -
Article: The critical line of two-flavor QCD at finite isospin or baryon densities from imaginary chemical potentials
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ABSTRACT: We determine the (pseudo)critical lines of QCD with two degenerate staggered fermions at nonzero temperature and quark or isospin density, in the region of imaginary chemical potentials; analytic continuation is then used to prolongate to the region of real chemical potentials. We obtain an accurate determination of the curvatures at zero chemical potential, quantifying the deviation between the case of finite quark and of finite isospin chemical potential. Deviations from a quadratic dependence of the pseudocritical lines on the chemical potential are clearly seen in both cases: we try different extrapolations and, for the case of nonzero isospin chemical potential, confront them with the results of direct Monte Carlo simulations. Finally we find that, as for the finite quark density case, an imaginary isospin chemical potential can strengthen the transition till turning it into strong first order.02/2012; -
Article: Phase diagram of QCD with two degenerate staggered quarks
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ABSTRACT: We present preliminary results about the critical line of QCD with two degenerate staggered quarks at nonzero temperature and chemical potential, obtained by the method of analytic continuation. As in our previous studies with different numbers of colors and flavors, we find deviations from a simple quadratic dependence on the chemical potential. We comment on the shape of the critical line at real chemical potential and give an estimate of the curvature of the critical line, both for quark chemical potential and isospin chemical potential.10/2011; -
Article: The Trivial Higgs at LHC
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ABSTRACT: We further elaborate on our proposal for the Trivial Higgs that within the Standard Model is the unique possibility to implement the spontaneous symmetry breaking of the local gauge symmetry by elementary local scalar fields. The Trivial Higgs boson turns out to be rather heavy with mass $m_H \simeq 750$ GeV. We discuss the experimental signatures of our Trivial Higgs and compare with the recent data from ATLAS and CMS collaborations based on a total integrated luminosity between 1 fb$^{-1}$ and 2.3 fb$^{-1}$. We suggest that the available experimental data could be consistent with our scenario.09/2011; -
Article: The trivial Higgs boson: first evidences from LHC
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ABSTRACT: We further elaborate on the triviality and spontaneous symmetry breaking scenario where the Higgs boson without self-interaction coexists with spontaneous symmetry breaking. The trivial Higgs boson is rather heavy with mass m_H = 754 +/- 20 (stat) +/- 20 (syst) GeV and total width \Gamma(H) \simeq 320 GeV. We briefly discuss the experimantal signatures of our trivial Higgs and compare with the recent results from ATLAS collaboration. We argue that experimental data seem to support our scenario.06/2011; -
Article: The critical line of QCD with four degenerate quarks
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ABSTRACT: We determine the pseudo-critical couplings at imaginary chemical potentials by high-statistics Monte Carlo simulations of QCD with four degenerate quarks at non-zero temperature and baryon density by the method of analytic continuationan. We reveal deviations from the simple quadratic dependence on the chemical potential visible in earlier works on the same subject. Finally, we discuss the implications of our findings for the shape of the pseudo-critical line at real chemical potential, comparing different possible extrapolations. Comment: 7 pages, 7 figures, talk presented at the XXVIII International Symposium on Lattice Field Theory, June 14-19, 2010, Villasimius, Sardinia, Italy12/2010; -
Article: Analytic continuation in QCD-like theories at finite density and finite isospin
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ABSTRACT: The method of analytic continuation is one of the most powerful tools to circumvent the sign problem in lattice QCD. The present study is part of a larger project which, based on the investigation of QCD-like theories which are free of the sign problem, is aimed at testing the validity of the method of analytic continuation and at improving its predictivity, in view of its application to real QCD. We have shown that a considerable improvement can be achieved if suitable functions are used to interpolate data with imaginary chemical potential. We present results obtained in a theory free of the sign problem such as two-color QCD at finite chemical potential. Comment: 8 pages, 6 figures, Contribution to The XXVII International Symposium on Lattice Field Theory, Beijing, July 25-31, 200901/2010; -
Article: Analytic continuation in two-color QCD: new results on the critical line
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ABSTRACT: We test the method of analytic continuation from imaginary to real chemical potential in two-color QCD, which is free from the sign problem. In particular, we consider the analytic continuation of the critical line to real values of the chemical potential. Comment: 4 pages, 2 figures, Strong and ElectroWeak Matter Amsterdam, the Netherlands, 26-29 August 200812/2008; -
Article: Analytical continuation from imaginary to real chemical potential in 2-color QCD under scrutiny
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ABSTRACT: The method of analytical continuation from imaginary to real chemical potential is tested in 2-color QCD. In comparison to previous studies in the same theory, an exact updating algorithm is used and simulations are performed closer to the thermodynamic limit. It is shown that the method considerably improves if suitable functions are used to interpolate data with imaginary chemical potential. Comment: 7 pages, 5 figures, Lattice 2006 (High Temperature and Density)10/2006; -
Article: Large logarithmic rescaling of the scalar condensate: a subtlety with substantial phenomenological implications
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ABSTRACT: Lattice data, taken since 1998 near the critical line of a 4D Ising model, have been supporting the large logarithmic rescaling of the scalar condensate predicted in the alternative description of symmetry breaking proposed by Consoli and Stevenson. This conclusion has been challenged in a recent paper by Balog et al. In this paper we respond to the criticism of these authors, recapitulate the theoretical and numerical evidences in favour of the alternative interpretation of `triviality' and reiterate our conclusion: `triviality', by itself, cannot be used to place upper bounds on the Higgs boson mass.02/2005; -
Article: Large logarithmic rescaling of the scalar condensate: new lattice evidences
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ABSTRACT: Using two different methods, we have determined the rescaling of the scalar condensate $Z\equiv Z_\phi$ near the critical line of a 4D Ising model. Our lattice data, in agreement with previous numerical indications, support the behavior $Z_\phi\sim \ln ({\Lambda})$, $\Lambda$ being the ultraviolet cutoff. This result is predicted in an alternative description of symmetry breaking where there are no upper bounds on the Higgs boson mass from `triviality'.08/2004; -
Article: Lattice measurement of the rescaling of the scalar condensate
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ABSTRACT: We have determined the rescaling of the scalar condensate $Z\equiv Z_\phi$ near the critical line of a 4D Ising model. Our lattice data, supporting previous numerical indications, confirm the behaviour $Z_\phi\sim \ln ({\rm cutoff})$. This result is predicted in an alternative description of symmetry breaking where there are no upper bounds on the Higgs boson mass from `triviality'.12/2003; -
Article: Investigations on the deconfining phase transition in QCD
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ABSTRACT: We investigate the deconfining phase transition in SU(3) pure gauge theory and in full QCD with two flavors of staggered fermions by means of a gauge invariant thermal partition functional. In the pure gauge case our finite size scaling analysis is in agreement with the well known weak first order phase transition. In the case of 2 flavors full QCD we find that the phase transition is consistent with weak first order, contrary to the expectation of a crossover for not too large quark masses.10/2003; -
Article: Indications on the Higgs boson mass from lattice simulations
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ABSTRACT: The `triviality' of $\Phi^4_4$ has been traditionally interpreted within perturbation theory where the prediction for the Higgs boson mass depends on the magnitude of the ultraviolet cutoff $\Lambda$. This approach crucially assumes that the vacuum field and its quantum fluctuations rescale in the same way. The results of the present lattice simulation, confirming previous numerical indications, show that this assumption is not true. As a consequence, large values of the Higgs mass $m_H$ can coexist with the limit $\Lambda\to \infty $. As an example, by extrapolating to the Standard Model our results obtained in the Ising limit of the one-component theory, one can obtain a value as large as $m_H=760 \pm 21$ GeV, independently of $\Lambda$. Comment: 3 pages, 2 figures, Lattice2003(higgs)09/2003; -
Article: Monopole Condensation in full QCD using the Schroedinger Functional
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ABSTRACT: We use a lattice thermal partition functional to study Abelian monopole condensation in full QCD with $N_f=2$ staggered fermions. We present preliminary results on $16^3\times4$ and $32^3\times4$ lattices.10/2002; -
Article: Abelian chromomagnetic background field at finite temperature on the lattice
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ABSTRACT: The vacuum dynamics of SU(2) and SU(3) lattice gauge theories is studied by means of a gauge-invariant effective action defined using the lattice Schr\"odinger functional at finite temperature. In the case of the SU(3) gauge theory numerical simulations are performed both at zero and finite temperature. The vacuum is probed using an external constant Abelian chromomagnetic field. At zero temperature, in agreement with our previous studies for the SU(2) theory, the external field is totally screened in the continuum limit. At finite temperature numerical data suggest that confinement is restored by increasing the strength of the applied field.03/2001; -
Article: Lattice measurement of the energy-gap in a spontaneously broken phase
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ABSTRACT: Using lattice simulations of a one-component $(\lambda \Phi^4)_4$ theory, we have measured the energy spectrum $\omega({\mathbf{k}})$ in the broken phase at various lattice sizes. Our data show that the energy-gap $\omega(0)$ is {\it not} the `Higgs mass' $M_h$ but an infrared-sensitive quantity that becomes smaller and smaller by increasing the lattice size and may even vanish in the infinite-volume limit.02/2001; -
Article: Lattice measurement of the scalar propagator near the symmetry breaking phase transition
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ABSTRACT: Recent lattice simulations of $(\lambda \Phi^4)_4$ theories in the broken phase show that : a) the shifted field propagator is well reproduced by the simple 2-parameter form ${{Z_{\rm prop}}\over{p^2 + M^2_h}}$ at finite momenta but strongly differs for $p \to 0$ b) the bare zero-momentum two-point function $\Gamma_2(0)= \frac{d^2 V_{\rm eff}}{d \phi^2_B}|_{\phi_B= \pm v_B}$ gives a value of $Z_\phi \equiv {{M^2_h}\over{\Gamma_2(0)}}$ that increases when approaching the continuum limit. This supports theoretical expectations where $v_B$ is related by an infinite re-scaling to the `physical Higgs condensate' $v_R$ defined through $\frac{d^2 V_{\rm eff}}{d \phi^2_R}|_{\phi_R= \pm v_R}=M^2_h$. New lattice data collected around the phase transition confirm this scenario. By denoting $M_{\rm SB} \equiv M_h ={\cal O} (v_R)$ the scale of the broken phase, our results suggest the existence of a `hierarchy' of scales $\Gamma_2(0) \ll M^2_{\rm SB} \ll v^2_B$ that become infinitely far in the continuum limit. This may open unexpected possibilities to reconcile an infinitesimal slope of the effective potential with finite values of $M_h$ and accomodate very different mass scales in the framework of a spontaneously broken theory.02/2001; -
Article: Magnetic condensation and confinement in lattice gauge theory
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ABSTRACT: We investigate Abelian monopoles and Abelian vortices condensation in finite temperature SU(2) and SU(3) pure lattice gauge theories.Nuclear Physics B - Proceedings Supplements. 10/2000; -
Article: A gauge invariant study of the monopole condensation in non Abelian lattice gauge theories
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ABSTRACT: We investigate the Abelian monopole condensation in finite temperature SU(2) and SU(3) pure lattice gauge theories. To this end we introduce a gauge invariant disorder parameter built up in terms of the lattice Schr\"odinger functional. Our numerical results show that the disorder parameter is different from zero and Abelian monopole condense in the confined phase. On the other hand our numerical data suggest that the disorder parameter tends to zero, in the thermodynamic limit, when the gauge coupling constant approaches the critical deconfinement value. In the case of SU(3) we also compare the different kinds of Abelian monopoles which can be defined according to the choice of the Abelian subgroups. Comment: 18 pages, 7 figures, LaTeX06/2000;
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Institutions
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1994–2000
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Università degli Studi di Bari Aldo Moro
Bari, Apulia, Italy
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