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Paolo Castorina

Publications and source records attributed to Paolo Castorina.

34 records · Page 2Linked to original sources
arXiv2013

Thermodynamics of the Quark-Gluon Plasma in Terms of Quasiparticles and Polyakov Line Condensates

We study a model of quark-gluon plasma of 2+1 flavors Quantum Chromodynamics in terms of quasiparticles propagating in a condensate of Polyakov loops. The Polyakov loop is coupled to quasiparticles by means of a gas-like effective potential. This study is useful to identify the effective degrees of freedom propagating in the medium above the critical temperature. Our finding is that a dominant part of the phase transition dynamics is accounted for by the Polyakov loop, hence the thermodynamics can be described without the need for rapidly increasing quasiparticle masses as $T \rightarrow T_c$, at variance respect to standard quasiparticle models.

hep-ph↗
arXiv2012

Quasiparticles and $Z(N)-$ lines in Hot Yang-Mills theories

In this talk we review, the quasiparticle description of the hot Yang-Mills theories, in which the quasiparticles propagate in (and interact with) a background field related to Z(N)-lines. We compare the present description with a more common one in which the effects of the Z(N)-lines are neglected. We show that it is possible to take into account the nonperturbative effects at the confinement transition temperature even without a divergent quasiparticle mass.

hep-ph↗
arXiv2012

Holographic Bound in Quantum Field Energy Density and Cosmological Constant

The cosmological constant problem is reanalyzed by imposing the limitation of the number of degrees of freedom (d.o.f.) due to entropy bounds directly in the calculation of the energy density of a field theory. It is shown that if a quantum field theory has to be consistent with gravity and holography, i.e. with an upper limit of storing information in a given area, the ultraviolet momentum cut-off is not the Planck mass, M_p, as naively expected, but M_p/N_U^(1/4) where N_U is the number of d.o.f. of the universe. The energy density evaluation turns out completely consistent with Bousso's bound on the cosmological constant value. The scale M_p/N_U^(1/4), that in the "fat graviton" theory corresponds to the graviton size, originates by a selfsimilar rearrangement of the elementary d.o.f. at different scales that can be seen as an infrared-ultraviolet connection.

hep-th↗
arXiv2011

Trace Anomaly and Quasi-Particles in Finite Temperature SU(N) Gauge Theory

We consider deconfined matter in SU(N) gauge theory as an ideal gas of transversely polarized quasi-particle modes having a temperature-dependent mass m(T). Just above the transition temperature, the mass is assumed to be determined by the critical behavior of the energy density and the screening length in the medium. At high temperature, it becomes proportional to T as the only remaining scale. The resulting (trace anomaly based) interaction measure Delta=(e - 3P)/T^4 and energy density are found to agree well with finite temperature SU(3) lattice calculations.

hep-ph↗
arXiv2007

Inhomogeneous phase of a Gluon Plasma at finite temperature and density

By considering the non-perturbative effects associated with the fundamental modular region, a new phase of a Gluon Plasma at finite density is proposed. It corresponds to the transition from glueballs to non-perturbative gluons which condense at a non vanishing momentum. In this respect the proposed phase is analogous to the color superconducting LOFF phase for fermionic systems.

hep-ph↗
arXiv2007

Effective degrees of freedom and gluon condensation in the high temperature deconfined phase

The Equation of State and the properties of matter in the high temperature deconfined phase are analyzed by a quasiparticle approach for $T> 1.2~T_c$. In order to fix the parameters of our model we employ the lattice QCD data of energy density and pressure. First we consider the pure SU(3) gluon plasma and it turns out that such a system can be described in terms of a gluon condensate and of gluonic quasiparticles whose effective number of degrees of freedom and mass decrease with increasing temperature. Then we analyze QCD with finite quark masses. In this case the numerical lattice data for energy density and pressure can be fitted assuming that the system consists of a mixture of gluon quasiparticles, fermion quasiparticles, boson correlated pairs (corresponding to in-medium mesonic states) and gluon condensate. We find that the effective number of boson degrees of freedom and the in-medium fermion masses decrease with increasing temperature. At $T \simeq 1.5 ~T_c$ only the correlated pairs corresponding to the mesonic nonet survive and they completely disappear at $T \simeq 2 ~T_c$. The temperature dependence of the velocity of sound of the various quasiparticles, the effects of the breaking of conformal invariance and the thermodynamic consistency are discussed in detail.

hep-ph↗
arXiv2005

Indications of a Pseudogap in the Nambu Jona-Lasinio model

The survival of \bar q q bound states at temperatures higher than the chiral restoration temperature, T_c, recently observed in lattice QCD, is discussed in the framework of the Nambu Jona-Lasinio model. The perturbative determination of the spectral function provides an indication of a pseudogap phase above T_c.

hep-ph↗
arXiv2005

On the Vacuum Cherenkov Radiation in Noncommutative Electrodynamics and the Elusive Effects of Lorentz Violation

We show that in the framework of noncommutative classical electrodynamics Cherenkov radiation is permitted in vacuum and we explicitly compute its spectrum at first order in the noncommutative parameter. We discuss the phenomenological impact of the merge of this new analysis with the old results of the substantial modification to the spectrum of the synchrotron radiation obtained in P.Castorina, A.Iorio and D.Zappala, Phys. Rev. D 69 (2004)065008. We propose to consider the pulsars' radiation spectrum - due to its very strong magnetic field - to investigate these Lorentz violating effects in astrophysical phenomena.

hep-ph↗
arXiv2005

Non-standard pairing in asymmetric trapped Fermi gases

We study an ultracold trapped Fermi gas of atoms in two hyperfine states with unequal populations. In this situation the usual BCS pairing is suppressed and non-standard pairing mechanisms become important. These are treated by solving the Bogoliubov-de Gennes equations, which at the same time correctly take into account the finite size of the trapped system. We find results which can be viewed as generalization of the LOFF phase to finite systems.

cond-mat.other↗
arXiv2005

Opinion dynamics and decision of vote in bipolar political systems

A model of the opinion dynamics underlying the political decision is proposed. The analysis is restricted to a bipolar scheme with a possible third political area. The interaction among voters is local but the final decision strongly depends on global effects such as, for example, the rating of the governments. As in the realistic case, the individual decision making process is determined by the most relevant personal interests and problems. The phenomenological analysis of the national vote in Italy and Germany has been carried out and a prediction of the next Italian vote as a function of the government rating is presented.

physics.soc-ph↗
arXiv2004

Energetic model of tumor growth

A macroscopic model of the tumor Gompertzian growth is proposed. This approach is based on the energetic balance among the different cell activities, described by methods of statistical mechanics and related to the growth inhibitor factors. The model is successfully applied to the multicellular tumor spheroid data.

q-bio.TO↗
arXiv2004

Tumor Gompertzian growth by cellular energetic balance

A macroscopic model of the tumor Gompertzian growth is proposed. The new approach is based on the energetic balance among the different cell activities, described by methods of statistical mechanics and related to the growth inhibitor factors. The model is successfully applied to the multicellular tumor spheroid data.

q-bio.CB↗
arXiv2004

Symmetry breaking in non-commutative cut-off field theories

The relation between symmetry breaking in non-commutative cut-off field theories and transitions to inhomogeneous phases in condensed matter and in finite density QCD is discussed. The non-commutative dynamics, with its peculiar infrared-ultraviolet mixing, can be regarded as an effective description of the mechanisms which lead to inhomogeneous phase transitions and a roton-like excitation spectrum.

hep-th↗
arXiv2004

Non-commutative dynamics and roton-like spectra in bosonic and fermionic condensates

The relation between symmetry breaking in non-commutative cut-off field theories and transitions to inhomogeneous phases in condensed matter is discussed. The non-commutative dynamics can be regarded as an effective description of the mechanisms which lead to inhomogeneous phase transitions and their relation to the roton-like excitation spectrum. The typical infrared-ultraviolet mixing in non-commutative theories contains the peculiar ingredients to describe the interplay between short and long distance particle interactions which is responsible for the non-uniform background and the roton spectrum both in bosonic and fermionic condensates.

hep-th↗