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P. Bozek

Publications and source records attributed to P. Bozek.

33 records · Page 2Linked to original sources
arXiv2002

Nuclear matter with off-shell propagation

Symmetric nuclear matter is studied within the conserving, self-consistent T-matrix approximation. This approach involves off-shell propagation of nucleons in the ladder diagrams. The binding energy receives contributions from the background part of the spectral function, away form the quasiparticle peak. The Fermi energy at the saturation point fulfills the Hugenholz-Van Hove relation. In comparison to the Brueckner-Hartree-Fock approach, the binding energy is reduced and the equation of state is harder

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arXiv2002

One-body Properties of Nuclear Matter with Off-shell Propagation

Symmetric nuclear matter is studied in the self-consistent, in-medium $T$-matrix approach. One-body spectral function, optical potential, and scattering width are calculated. Properties of quasi-particle excitations at the Fermi surface are discussed. Dispersive self-energies are dominated by contributions from the $^1S_0$, $3S_1-^3D_1$, and $^3P_1$ partial waves.

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arXiv2001

In medium T-matrix for superfluid nuclear matter

We study a generalized ladder resummation in the superfluid phase of the nuclear matter. The approach is based on a conserving generalization of the usual T-matrix approximation including also anomalous self-energies and propagators. The approximation here discussed is a generalization of the usual mean-field BCS approach and of the in medium T-matrix approximation in the normal phase. The numerical results in this work are obtained in the quasi-particle approximation. Properties of the resulting self-energy, superfluid gap and spectral functions are studied.

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arXiv2001

Thermodynamic consistency for nuclear matter calculations

We investigate the relation between the binding energy and the Fermi energy and between different expressions for the pressure in cold nuclear matter. For a self-consistent calculation based on a $Φ$ derivable $T-$matrix approximation with off-shell propagators the thermodynamic relations are well satisfied unlike for a $G-$matrix or a $T-$matrix approach using quasi-particle propagators in the ladder diagrams.

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arXiv2000

Reduction of superfluid gap by scattering

The effect nucleon dressing by scattering on the pairing gap in nuclear matter is discussed. Numerical results from self-consistent T-matrix calculations are compared to quasi-particle approximations. The dominant effect of scattering can be accounted for by a renormalization of the quasi-particle strength. The exponential sensitivity of the pairing gap and the critical temperature on the pairing strength makes it strongly dependent on many-body effects.

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arXiv1999

Semiclassical and quantum production rates

We discuss the effects of the off-shell nucleon propagation for the particle production. Results from nonequilibrium Kadanoff-Baym evolution modeling a heavy ion collision are presented. The production rates are compared to equilibrium emission rates obtained in the same approximation for the self-energy. The comparison of semiclassical and quantum in-medium production rates is performed within the T-matrix approximation. Self-consistent T-matrix resummation allows us to discuss also the effect of the off-shell propagation on the effective in-medium cross section.

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arXiv1999

Superfluid nuclear matter calculations

We present a method to calculate nuclear matter properties in the superfluid phase. The method is based on the use of self-consistent off-shell nucleon propagators in the T-matrix equation. Such a complete treatment of the spectral function, is required below and around $T_c$ due to a pseudogap formation in the spectral function. In the superfluid phase we introduce the anomalous self-energy in the fermion propagators and in the T-matrix equation, consistently with the strong coupling BCS equations. The equations for the nucleon spectral function include both a contribution of condensed and scattering pairs. The method is illustrated by numerical calculations. Above $T_c$ pseudogap formation is visible in the spectral function and below $T_c$ a superfluid gap also appears.

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arXiv1998

Self-consistent solution of Galitskii-Feynman equations at finite temperature

We solve the in-medium T-matrix equation at finite temperature including the off-shell propagation of nucleons. In this way a self-consistent spectral function for the nucleons is obtained. The results are compared to a calculation using the quasiparticle approximation in the T-matrix equation. Also the effective in-medium cross sections for the two cases are compared.

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arXiv1998

Particle production from off-shell nucleons

Particle production in equilibrium and nonequilibrium quantum systems is calculated. The effects of the off-shell propagation of nucleons in medium on the particle production are discussed. Comparision to the semiclassical production rate is given.

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arXiv1998

Spinodal and dynamical instabilities at the phase transition from the quark-gluon plasma to hadrons

The stability of an expanding parton plasma is analyzed within quasi-particle models. The effective mass of the parton is calculated self-consistently from a gap equation which is either obtained from the Nambu Jona-Lasinio Lagrangian or from a fit to observables calculated on the lattice. The latter shows an effective confinement. At thermal equilibrium the stability is studied within thermodynamics (mechanical stability) and via a linear response analysis of the Vlasov equation. The instabilities related to a first-order phase transition are found. For a plasma expanding in three and one dimensions far from equilibrium a new type of instability, called dynamical, appears. The relation to cluster formation is shown in a molecular dynamics calculation.

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arXiv1998

Transport theory with self-consistent confinement related to the lattice data

The space-time development of a quark-gluon plasma is calculated from a Vlasov equation for the distribution function of quasiparticles with medium dependent masses. At each space-time point the masses are calculated selfconsistently from a gap equation, whose form is determined by the requirement that in thermal equilibrium and for a range of temperatures the energy density of the quasi-particle system is identical to the one from lattice calculations . The numerical solutions of the Vlasov equation display confinement. Relations to effective theories like that by Friedberg Lee and Nambu Jona-Lasinio are established.

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arXiv1998

Observation of the Mott Effect in Heavy Ion Collisions

Possibility of observing the Mott momentum in the distribution of the deuterons produced in the process $p + n \to d + γ$, in the first stage of a nuclear reaction is presented. The correlation of a hard photon with a deuteron allows to select those deuterons produced at the beginning of a reaction.

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arXiv1997

Particle production in quantum transport theories

The particle production in the intermediate energy heavy ion collisions is discussed in the framework of the nonequilibrium Green's functions formalism. The evolution equations of the Green's functions for fermions allows for the discussion of the off-shell fermion propagator and of the large momentum component in the initial state. For the case of a homogeneous system numerical calculations of the meson production rate are performed and compared with the semiclassical production rate.

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arXiv1996

Time development of a density perturbation in the unstable nuclear matter

We present the solution of the time development of an unstable initial density perturbation in the linearized Vlasov equation, completing the previous analysis in the literature. The additional contributions found are usually damped and can be neglected at large times in the unstable region. The work clarifies also the problem of the normalization of the solution with respect to the initial perturbation of the density.

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