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Paolo Cea

Publications and source records attributed to Paolo Cea.

At least 73 records · Page 4Linked to original sources
arXiv2006

Full QCD in external chromomagnetic field

We investigate the deconfining phase transition in full QCD with two flavors of staggered fermions in presence of a constant abelian chromomagnetic field. We find that the deconfinement temperature decreases and eventually goes to zero by increasing the strength of the chromomagnetic field. Moreover our results suggest that the chiral transition coincides with the deconfinement transition and therefore even the chiral critical temperature depends on the applied chromomagnetic field. We also find that the chiral condensate increases with the strength of the chromomagnetic field.

hep-lat↗
arXiv2006

Light Curves of Swift Gamma Ray Bursts

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma ray bursts are characterized by a canonical behaviour of the X-ray afterglows. We present an effective theory which allows us to account for X-ray light curves of both (short - long) gamma ray bursts and X-ray rich flashes. We propose that gamma ray bursts originate from massive magnetic powered pulsars.

astro-ph↗
arXiv2006

Baryogenesis and CP-Violating Domain Walls in the Background of a Magnetic Field

Within the domain wall-mediated electroweak baryogenesis, we study fermion scattering off a CP-violating wall in the background of an uniform magnetic field. In particular, we calculate the asymmetry between the reflection coefficients for right-handed and left-handed chiral fermions, ΔR = R_{R \to L} - R_{L \to R}, which is of relevance to non local baryogenesis mechanisms.

astro-ph↗
arXiv2006

Probing the QCD Vacuum Using External Fields

The QCD vacuum can be studied using external fields. We report here results respectively obtained probing the lattice QCD vacuum by means of an abelian monopole field and of an abelian chromomagnetic field

hep-lat↗
arXiv2005

Magnetars: Structure and evolution from p-star models

P-stars are compact stars made of up and down quarks in $β$-equilibrium with electrons in a chromomagnetic condensate. We discuss p-stars endowed with super strong dipolar magnetic field which, following consolidated tradition in literature, are referred to as magnetars. We show that soft gamma-ray repeaters and anomalous $X$-ray pulsars can be understood within our theory. We find a well defined criterion to distinguish rotation powered pulsars from magnetic powered pulsars. We show that glitches, that in our magnetars are triggered by magnetic dissipative effects in the inner core, explain both the quiescent emission and bursts in soft gamma-ray repeaters and anomalous $X$-ray pulsars. We account for the braking glitch from SGR 1900+14 and the normal glitch from AXP 1E 2259+586 following a giant burst. We discuss and explain the observed anti correlation between hardness ratio and intensity. Within our magnetar theory we are able to account quantitatively for light curves for both gamma-ray repeaters and anomalous $X$-ray pulsars. In particular we explain the puzzling light curve after the June 18, 2002 giant burst from AXP 1E 2259+586.

astro-ph↗
arXiv2005

Deconfinement phase transitions in external fields

We compare vacuum dynamics of abelian versus non abelian lattice gauge theories in presence of external fields. We find that the deconfinement temperature of non abelian theories depends on the strength of a constant abelian chromomagnetic field end eventually goes to zero. On the contrary such an effect is not shared by abelian theories. We argue on the relevance of this result to understand the QCD vacuum.

hep-lat↗
arXiv2005

Color Dynamics in External Fields

We investigate the vacuum dynamics of U(1), SU(2), and SU(3) lattice gauge theories in presence of external (chromo)magnetic fields, both in (3+1) and (2+1) dimensions. We find that the critical coupling for the phase transition in compact U(1) gauge theory is independent of the strength of an external magnetic field. On the other hand we find that, both in (3+1) and (2+1) dimensions, the deconfinement temperature for SU(2) and SU(3) gauge systems in a constant abelian chromomagnetic field decreases when the strength of the applied field increases. We conclude that the dependence of the deconfinement temperature on the strength of an external constant chromomagnetic field is a peculiar feature of non abelian gauge theories and could be useful to get insight into color confinement.

hep-lat↗
arXiv2005

Magnetars

P-stars are compact stars made of up and down quarks in beta-equilibrium with electrons in a chromomagnetic condensate. P-stars are able to account for compact stars like RXJ 1856.5-3754 and RXJ 0720.4-3125, stars with radius comparable with canonical neutron stars, as well as super massive compact objects like SgrA*. We discuss p-stars endowed with super strong dipolar magnetic field which, following consolidated tradition in literature, are referred to as magnetars. We show that soft gamma-ray repeaters and anomalous X-ray pulsars can be understood within our theory. We find a well defined criterion to distinguish rotation powered pulsars from magnetic powered pulsars. We show that glitches, that in our magnetars are triggered by magnetic dissipative effects in the inner core, explain both the quiescent emission and bursts in soft gamma-ray repeaters and anomalous X-ray pulsars. We are able to account for the braking glitch from SGR 1900+14 and the normal glitch from AXP 1E 2259+586 following a giant burst. We discuss and explain the observed anti correlation between hardness ratio and intensity. Within our magnetar theory we are able to account quantitatively for light curves for both gamma-ray repeaters and anomalous X-ray pulsars. In particular we explain the puzzling light curve after the June 18, 2002 giant burst from AXP 1E 2259+586, so that we feel this last event as the Rosetta Stone for our theory. Finally, in Appendix we discuss the origin of the soft emission not only for soft gamma-ray repeaters and anomalous X-ray pulsars, but also for isolated X-ray pulsars. We also offer an explanation for the puzzling spectral features in 1E 1207.4-5209.

astro-ph↗
arXiv2004

P-Stars

P-Stars are a new class of compact stars made of up and down quarks in beta-equilibrium with electrons in an Abelian chromomagnetic condensate. We show that P-Stars are able to account for compact stars with R < 6 Km, as well as stars with radius comparable with canonical Neutron Stars. We find that cooling curves of P-Stars compare rather well with observational data. We suggest that P-Matter produced at the primordial deconfinement transition is a viable candidate for baryonic Cold Dark Matter. Finally, we show that P-Stars are able to overcome the gravitational collapse even for mass much greater than 10^6 Solar Mass.

astro-ph↗
arXiv2004

On the Pulsar Emission Mechanism

We discuss a general mechanism which allows to explain naturally both radio and high energy emission by pulsars. We also discuss the plasma distribution in the region surrounding the pulsar, the pulsar wind and the formation of jet along the magnetic axis. We suggest a plausible mechanism to generate pulsar proper motion velocities.

astro-ph↗
arXiv2004

RXJ1856.5-3754 and RXJ0720.4-3125 are P-Stars

P-stars are a new class of compact stars made of up and down quarks in $β$-equilibrium with electrons in a chromomagnetic condensate. P-stars are able to account for compact stars with $R \lesssim 6 Km$, as well as stars comparable to canonical neutron stars. We show that P-stars once formed are absolutely stable, for they cannot decay into neutron or strange stars. We convincingly argue that the nearest isolated compact stars RXJ1856.5-3754 and RXJ0720.4-3125 could be interpreted as P-stars with $M \simeq 0.8 M_{\bigodot}$ and $R \simeq 5 Km$.

astro-ph↗
arXiv2004

The deconfining phase transition in full QCD with two dynamical flavors

We investigate the deconfining phase transition in SU(3) pure gauge theory and in full QCD with two flavors of staggered fermions. The phase transition is detected by measuring the free energy in presence of an abelian monopole background field. In the pure gauge case our finite size scaling analysis is in agreement with the well known presence of a weak first order phase transition. In the case of 2 flavors full QCD we find, using the standard pure gauge and staggered fermion actions, that the phase transition is consistent with weak first order, contrary to the expectation of a crossover for not too large quark masses and in agreement with results obtained by the Pisa group.

hep-lat↗
arXiv2002

Probing Confinement with Chromomagnetic Fields

Using the lattice Schrödinger functional we study vacuum dynamics of SU(3) gauge theory at finite temperature. The vacuum is probed by means of an external constant Abelian chromomagnetic field. We find that by increasing the strength of the applied external field the deconfinement temperature decreases towards zero. This implies that strong enough Abelian chromomagnetic fields destroy confinement of color.

hep-lat↗
arXiv2002

Abelian chromomagnetic fields and confinement

We study vacuum dynamics of SU(3) lattice gauge theory at finite temperature using the lattice Schrödinger functional. The SU(3) vacuum is probed by means of an external constant Abelian chromomagnetic field. We find that by increasing the strength of the applied external field the deconfinement temperature decreases towards zero. This means that strong enough Abelian chromomagnetic fields destroy confinement of color. We discuss some consequences of this phenomenon on confinement and quark stars.

hep-lat↗
arXiv2002

Study of Confinement Using the Schroedinger Functional

We use a gauge-invariant effective action defined in terms of the lattice Schroedinger functional to investigate vacuum dynamics and confinement in pure lattice gauge theories. After a brief introduction to the method, we report some numerical results.

hep-lat↗
arXiv2001

Abelian monopole and vortex condensation in lattice gauge theories

We study Abelian monopole and vortex condensation in lattice pure gauge theories. Condensation is detected by means of a disorder parameter defined in terms of a gauge-invariant effective action introduced using the lattice Schrödinger functional. Dirac monopoles condense in the confined phase of U(1) lattice gauge theory. Abelian monopoles and Abelian vortices condense in the confined phase of SU(2) and SU(3) lattice gauge theories.

hep-lat↗
arXiv2001

External Field Dependence of Deconfinement Temperature in SU(3)

We study vacuum dynamics of SU(3) lattice gauge theory at finite temperature. Using the lattice Schrödinger functional, SU(3) vacuum is probed by means of an external constant Abelian chromomagnetic field. Our preliminary numerical data suggest that, by increasing the strength of the applied external field, deconfinement temperature decreases towards zero. This means that strong enough Abelian chromomagnetic fields destroy confinement of color.

hep-lat↗