Spin and total angular momentum of the glue

We briefly review the present theoretical and experimental knowledge on Delta_g and J_g.Comment: 8 pages, 2 figures, Proceed. Second International Conference on Perspectives in Hadronic Physics. Miramare - Trieste, Italy, May 199

Combustion of a hadronic star into a quark star: the turbulent and the diffusive regimes

We argue that the full conversion of a hadronic star into a quark or a hybrid star occurs within two different regimes separated by a critical value of the density of the hadronic phase $\overline{n_h}$. The first stage, occurring for $n_h>\overline{n_h}$, is characterized by turbulent combustion and lasts typically a few ms. During this short time-scale neutrino cooling is basically inactive and the star heats up thanks to the heat released in the conversion. In the second stage, occurring for $n_h<\overline{n_h}$, turbulence is not active anymore, and the conversion proceeds on a much longer time scale (of the order of tens of seconds), with a velocity regulated by the diffusion and the production of strange quarks. At the same time, neutrino cooling is also active. The interplay between the heating of the star due to the slow conversion of its outer layers (with densities smaller than $\overline{n_h}$) and the neutrino cooling of the forming quark star leads to a quasi-plateau in the neutrino luminosity which, if observed, would possibly represent a unique signature for the existence of quark matter inside compact stars. We will discuss the phenomenological implications of this scenario in particular in connection with the time structure of long gamma-ray-bursts.Comment: 12 pages, 5 figure

Probing the composition of sub-millisecond rotating compact stars by r-modes instability

We investigate the implications of the r-modes instability on the composition of a compact star rotating at a sub-millisecond period. In particular, the only viable astrophysical scenario for such an object, wich might present inside the Low Mass X-ray Binary associated with the x-ray transient XTE J1739-285, is that it has a strangeness content. Since previous analysis indicate that hyperonic stars or stars containing a kaon condensate are unlikely because of the mass-shedding constraint, the only remaining possibility is that such an object is either a strange quark star or a hybrid quark-hadron star

The scenario of two families of compact stars 2. Transition from hadronic to quark matter and explosive phenomena

We will follow the two-families scenario described in the accompanying paper, in which compact stars having a very small radius and masses not exceeding about 1.5$M_\odot$ are made of hadrons, while more massive compact stars are quark stars. In the present paper we discuss the dynamics of the transition of a hadronic star into a quark star. We will show that the transition takes place in two phases: a very rapid one, lasting a few milliseconds, during which the central region of the star converts into quark matter and the process of conversion is accelerated by the existence of strong hydrodynamical instabilities, and a second phase, lasting about ten seconds, during which the process of conversion proceeds till the surface of the star via production and diffusion of strangeness. We will show that these two steps play a crucial role in the phenomenological implications of the model. We will discuss the possible implications of this scenario both for long and for short Gamma Ray Bursts, using the proto-magnetar model as the reference frame of our discussion. We will show that the process of quark deconfinement can be connected to specific observed features of the GRBs. In the case of long GRBs we will discuss the possibility that quark deconfinement is at the origin of the second peak present in quite a large fraction of bursts. Also we will discuss the possibility that long GRBs can take place in binary systems without being associated with a SN explosion. Concerning short GRBs, quark deconfinement can play the crucial role in limiting their duration. Finally we will shortly revisit the possible relevance of quark deconfinement in some specific type of Supernova explosions, in particular in the case of very massive progenitors.Comment: 15 pages, 9 figures, prepared for the 2015 EPJA Topical Issue on "Exotic Matter in Neutron Stars". Revised versio

A chiral quark-soliton model with broken scale invariance for nuclear matter

We present a model for describing nuclear matter at finite density based on quarks interacting with chiral fields, \sigma and \pi and with vector mesons introduced as massive gauge fields. The chiral Lagrangian includes a logarithmic potential, associated with the breaking of scale invariance. We provide results for the soliton in vacuum and at finite density, using the Wigner-Seitz approximation. We show that the model can reach higher densities respect to the linear-\sigma model and that the introduction of vector mesons allows to obtain saturation. This result was never obtained before in similar approaches.Comment: 14 pages, 15 figures, 7 tables. Enlarged version including vector meson

A hybrid-chiral soliton model with broken scale invariance for nuclear matter

We present a model for describing nuclear matter at finite density based on quarks interacting with chiral fields, sigma and pion. The chiral Lagrangian also includes a logarithmic potential, associated with the breaking of scale invariance. We provide results for the soliton in vacuum and at finite density, using the Wigner-Seitz approximation. We show that the model can reach higher densities respect to the Linear-sigma model, up to approximately 3 rho_0 for m_sigma=1200 MeV.Comment: 7 pages, 3 figures, Proceedings of Cortona 2011 XIII Convegno su Problemi di Fisica Nucleare Teoric

Polarized sea measurements at JPARC

Large double spin-asymmetries can be foreseen for Drell-Yan production in $p p$ scattering at JPARC energies. The sign of the asymmetries can be used to discriminate between different model calculations of sea quark distributions.Comment: 4 pages, 2 figures, Proceedings of DIS2006, Kyoto 200

Connection between Distribution and Fragmentation Functions

We show that the quark fragmentation function $D(z)$ and the quark distribution function $q(x)$ are connected in the $z \to 1$ limit by the approximate relation $D(z)/z \simeq q(2-1/z)$, where both quantities are in their physical regions. Predictions for proton production in inelastic $e^+ e^-$ annihilation, based on the new relation and standard parametrizations of quark distribution functions, are found to be compatible with the data.Comment: 10 latex pages, 2 figures, published as Rapid Communication in PR