119248374
Exploring the role of model parameters and regularization procedures in the thermodynamics of the PNJL model
The equation of state and the critical behavior around the critical end point are studied in the framework of the Polyakov‐Nambu‐Jona‐Lasinio model. We prove that a convenient choice of the model parameters is crucial to get the correct description of isentropic trajectories. The physical relevance of the effects of the regularization procedure is insured by the agreement with general thermodynamic requirements. The results are compared with simple thermodynamic expectations and lattice data.
118491126
Scalar-pseudoscalar meson behavior and restoration of symmetries in SU(3) PNJL model
The modification of mesonic observables in a hot medium is analyzed as a tool to investigate the restoration of chiral and axial symmetries in the context of the Polyakov-loop extended Nambu--Jona-Lasinio model. The results of the extended model lead to the conclusion that the effects of the Polyakov loop are fundamental for reproducing lattice findings. In particular, the partial restoration of the chiral symmetry is faster in the PNJL model than in the NJL one, and it is responsible for several effects: the meson-quark coupling constants show a remarkable difference in both models, there is a faster tendency to recover the Okubo-Zweig-Iizuka rule, and finally the topological susceptibility nicely reproduces the lattice results around $T/T_c\approx 1.0$.
14365411
A consistent approximation scheme beyond RPA for bosons
Abstract:In this paper, we develop a consistent extension of RPA for bosonic systems. In order to illustrate the method, we consider the case of the anharmonic oscillator. We compare our results with those obtained in mean-field and standard RPA approaches with the exact ones and show that they are very close to these ones.
17678438
Long distance expansion for the NJL model with SU(3) and UA(1) breaking
This work is a follow up of recent investigations, where we study the implications of a generalized heat kernel expansion, constructed to incorporate non-perturbatively the effects of a non-commutative quark mass matrix in a fully covariant way at each order of the expansion. As underlying Lagrangian we use the Nambu–Jona-Lasinio model of QCD, with SUf(3) and UA(1) breaking, the latter generated by the 't Hooft flavour determinant interaction. The associated bosonized Lagrangian is derived in leading stationary phase approximation (SPA) and up to second order in the generalized heat kernel expansion. Its symmetry breaking pattern is shown to have a complex structure, involving all powers of the mesonic fields allowed by symmetry. The considered Lagrangian yields a reliable playground for the study of the implications of symmetry and vacuum structure on the mesonic spectra, which we evaluate for the scalar and pseudoscalar meson nonets and compare with other approaches and experiment.
119243899
The QCD Critical End Point in the Context of the Polyakov--Nambu--Jona-Lasinio Model
We investigate the phase diagram of the so-called Polyakov--Nambu--Jona-Lasinio model at finite temperature and nonzero chemical potential with three quark flavors. Chiral and deconfinement phase transitions are discussed, and the relevant order-like parameters are analyzed. A special attention is payed to the critical end point (CEP): the influence of the strangeness on the location of the CEP is studied; also the strength of the flavor-mixing interaction alters the CEP location, once when it becomes weaker the CEP moves to low temperatures and can even disappear.
18083314
Random phase approximation and extensions applied to a bosonic field theory
Abstract:An application of a self-consistent version of RPA to quantum field theory with broken symmetry is presented. Although our approach can be applied to any bosonic field theory, we specifically study the ϕ4 theory in 1 + 1 dimensions. We show that the standard RPA approach leads to an instability which can be removed when going to a superior version, i.e. the renormalized RPA. We present a method based on the so-called charging formula of the many-electron problem to calculate the correlation energy and the RPA effective potential.
135763
Landau-Pomeranchuk-Migdal effect for multihundred GeV electrons
Experimental results for the bremsstrahlung energy loss of 149, 207, and 287 GeV electrons in thin Ir, Ta, and Cu targets are presented. For each target and energy, a comparison between simulated values based on the Landau-Pomeranchuk-Migdal (LPM) suppression of incoherent bremsstrahlung is shown. For the electron energies investigated, the LPM effect enters the quantum regime where the recoil imposed on the electron by the emitted photon becomes important. Good agreement between simulations based on Migdal's theory and data from the experiment is found, indicating that the LPM suppression is well understood also in the quantum regime. Results from a comparison between simulations with the "threshold" energy E