118497947
Properties of the Boltzmann equation in the classical approximation
We study the Boltzmann equation with elastic point-like scalar interac-tions in two different versions of the the classical approximation. Although solving numerically the Boltzmann equation with the unapproximated col-lision term poses no problem, this allows one to study the effect of the ultraviolet cutoff in these approximations. This cutoff dependence in the classical approximations of the Boltzmann equation is closely related to the non-renormalizability of the classical statistical approximation of the underlying quantum field theory. The kinetic theory setup that we con-sider here allows one to study in a much simpler way the dependence on the ultraviolet cutoff, since one has also access to the non-approximated result for comparison.
119251781
Looking inside neutron stars: Microscopic calculations confront observations
While QCD appears not to be accurately solvable in the regime of interest for neutron star physics, microscopic calculations are feasible at both low and very high densities. In this work, we propose using the most realistic calculations in these two regimes of nuclear physics and perturbative QCD, and construct equations of state by matching the results requiring thermodynamic consistency. We find that the resulting equations of state --- in contrast to several hadronic ones --- are able to reproduce current observational data on neutron stars without any fine tuning, and allow stable hybrid stars with masses up to 2.1M_{sun}. Using recent observations of star radii, we perform a maximum likelihood analysis to further constrain the equation of state, and in addition show that the effects of rotation on radii and masses should not be neglected in future precision studies.
118447664
Nonrenormalizability of the classical statistical approximation
In this paper, we discuss questions related to the renormalizability of the classical statistical approximation, an approximation scheme that has been used recently in several studies of out-of-equilibrium problems in Quantum Field Theory. Although the ultraviolet power counting in this approximation scheme is identical to that of the unapproximated quantum field theory, this approximation is not renormalizable. The leading cause of this non-renormalizability is the breakdown of Weinberg's theorem in this approximation. We also discuss some practical implications of this negative result for simulations that employ this approximation scheme, and we speculate about a possible modification of the classical statistical approximation in order to systematically subtract the leading residual divergences.
17627816
Exclusive vs. diffractive vector meson production in DIS at small x or off nuclei
The diffractive production of vector mesons in deep inelastic scattering (DIS) is calculated in the McLerran-Venugopalan model. This is relevant when large parton densities are probed by the virtual photon, as is the case at small Bjorken x or in DIS off nuclei. We investigate differences between the exclusive production (when the target doesn't break up) which dominates at small momentum transfer squared |t|, and the diffractive production (when the target scatters inelastically) which dominates at large |t|.
119185980
Shock wave collisions in AdS5: approximate numerical solutions
We numerically study the evolution of a boost-invariant N=4 SYM medium using AdS/CFT. We consider a toy model for the collision of gravitational shock waves, finding that the energy density first increases, reaches a maximum and then starts to decrease, matching hydrodynamics for late times. For the initial conditions we consider, the hydrodynamic scale governing the late time behaviour is to very good approximation determined by the area of the black hole horizon at initial times. Our results provide a toy model for the early time evolution of the bulk system in heavy-ion collisions at RHIC and the LHC.
119193077
On p⊥-broadening of high energy partons associated with the LPM effect in a finite-volume QCD medium
We study the contributions from radiation to p⊥-broadening of a high energy parton traversing a QCD medium with a finite length L. The interaction between the parton and the medium is described by decorrelated static multiple scattering. Amplitudes of medium-induced gluon emission and parton self-energy diagrams are evaluated in the soft gluon limit in the BDMPS formalism. We find both the double-logarithmic correction from incoherent scattering, which is parametrically the same as that in single scattering, and the logarithmic correction from the LPM effect. Therefore, we expect a parametrically large correction from radiation to the medium-induced p⊥-broadening in perturbative QCD.
28663874
Modelling of the ALICE data acquisition system
The Heavy Ion Experiment ALICE is one of the three experiments at the LHC accelerator at CERN. Modeling and simulation of the large scale ALICE Data Acquisition (DAQ) system is necessary in order to study the behavior of the system. The development of a simulator -- ALSIM for the ALICE Data Acquisition System -- is described. ALSIM models front-end data readout, event building, data reduction and data storage. Technology dependent implementations can be linked in various topologies can be defined dynamically by means of description files. The simulation environment will be described as well as details of the model.
196069470
Reference Manual and User's Manual for ALICE DAQ Modelling and Simulation