Hybrid neutron stars within the Nambu-Jona-Lasinio model and confinement

Recently, it has been shown that the standard Nambu-Jona-Lasinio (NJL) model is not able to reproduce the correct QCD behavior of the gap equation at large density, and therefore a different cutoff procedure at large momenta has ben proposed. We found that, even with this density dependent cutoff procedure, the pure quark phase in neutron stars (NS) interiors is unstable, and we argue that this could be related to the lack of confinement in the original NJL model.Comment: 2 pages, 1 figure, to be published in the proceedings of the conference EXOCT07, Catania, 11-15 June, 200

The ideal relativistic spinning gas: polarization and spectra

We study the physics of the ideal relativistic rotating gas at thermodynamical equilibrium and provide analytical expressions of the momentum spectra and polarization vector for the case of massive particles with spin 1/2 and 1. We show that the finite angular momentum J entails an anisotropy in momentum spectra, with particles emitted orthogonally to J having, on average, a larger momentum than along its direction. Unlike in the non-relativistic case, the proper polarization vector turns out not to be aligned with the total angular momentum with a non-trivial momentum dependence.Comment: Final published version. Minor corrections to formula

Improving crowd behaviour for emergency simulation using game-captured data.

Crowd simulation has become an essential asset in many different industries, ranging from games and movies to engineering and construction; while the requirements might vary significantly between these domains, the underlying theory is shared among them. Emergency simulation in particular is a field that has made great use of crowd simulation to validate and improve building design and layouts, allowing architects to determine how a building would cope in case of an evacuation and determine the estimated egress time and survival rate. Existing algorithms and techniques are usually organised in two layers: a high level component determines the actions and goals of each agent that is participating in the simulation while the low level component is responsible for the movement of the agent. Steering behaviours [Reynolds 1987] are usually employed for movement, but they don’t take into account more nuanced aspects of agents behaviour like their internal state, priorities and system of beliefs [Pelechano et al. 2007]. This is particularly important for emergency simulations as individuals react in different ways under stressful circumstances and factors like fatigue and caring for others must be taken into account to provide an accurate simulation

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.Comment: 5 pages, 2 figure

Non-extensivity Parameter of Thermodynamical Model of Hadronic Interactions at LHC energies

The LHC measurements above SPS and Tevatron energies give the opportunity to test predictions of non-extensive thermodynamical picture of hadronic interaction to examine measured transverse momenta distributions for new interaction energy range. We determined Tsallis model non-extensivity parameter for the hadronization process before short-lived particles decayed and distort the initial p_t distribution. We have shown that it follows exactly smooth rise determined at lower energies below present LHC record. The shape of the q parameter energy dependence is consistent with expectations and the evidence of the asymptotic limit may be seen.Comment: 2 pages, 2 figure

Noncommutative electrodynamics and ultra high energy gamma rays

Plane waves in noncommutative classical electrodynamics (NCED) have a peculiar dispersion relation. We investigate the kinematical conditions on this deformed "mass shell" which come from ultra high energy gamma rays and discuss noncommutative dynamical effects on the gamma absorption by the infrared background and on the intrinsic spectrum. Finally we note that in NCED there is a strong correlation between the modified dispersion relation and the presence of dynamical effects in electromagnetic phenomena such as in the case of the synchrotron radiation. From this point of view, the limits on the typical energy scale of the violation of Lorentz invariance obtained by deformed dispersion relations and by assuming undeformed dynamical effects should be taken with some caution.Comment: Latex file, 7 pages, to be published in Europhysics Letter

Astrophysical constraints on the confining models : the Field Correlator Method

We explore the relevance of confinement in quark matter models for the possible quark core of neutron stars. For the quark phase, we adopt the equation of state (EoS) derived with the Field Correlator Method, extended to the zero temperature limit. For the hadronic phase, we use the microscopic Brueckner-Hartree-Fock many-body theory. We find that the currently adopted value of the gluon condensate $G_2 \simeq 0.006-0.007 \rm {GeV^4}$, which gives a critical temperature $T_c \simeq 170 \rm MeV$, produces maximum masses which are only marginally consistent with the observational limit, while larger masses are possible if the gluon condensate is increased.Comment: 7 pages, 5 figure

Predictions of hadron abundances in pp collisions at the LHC

Based on the statistical hadronization model, we obtain quantitative predictions for the relative abundances of hadron species in pp collisions at the LHC. By using the parameters of the model determined at sqrt s = 200 GeV, and extrapolating the overall normalization from ppbar collisions at the SPS and Tevatron, we find that the expected rapidity densities are almost grand-canonical. Therefore, at LHC the ratios between different species become essentially energy-independent, provided that the hadronization temperature T_H and the strangeness suppression factor gamma_S retain the stable values observed in the presently explored range of pp and ppbar collisions.Comment: 4 pages. Final version published in JP