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P. Szepfalusy

Publications and source records attributed to P. Szepfalusy.

11 recordsLinked to original sources
arXiv2005

Mapping the boundary of the first order finite temperature restoration of chiral symmetry in the m_pi-m_K--plane with a linear sigma model

The phase diagram of the three-flavor QCD is mapped out in the low mass corner of the m_pi-m_K--plane with help of the SU_L(3) x SU_R(3) linear sigma model (LSM). A novel zero temperature parametrization is proposed for the mass dependence of the couplings away from the physical point based on the the three-flavor chiral perturbation theory (U(3) ChPT). One-loop thermodynamics is constructed by applying optimized perturbation theory. The unknown dependence of the scalar spectra on the pseudoscalar masses limitates the accuracy of the predictions. Results are compared to lattice data and similar investigations with other variants of effective chiral models. The critical value of the pion mass is below 65 MeV for all m_K values <= 800 MeV. Along the diagonal m_pi=m_K, we estimate m_crit(diag)=40+-20 MeV.

hep-ph↗
arXiv2004

The nature of the soft excitation at the critical end point of QCD

Using a large flavor number expansion and a gap equation for the pion mass the chiral quark-meson model is solved at the lowest order in the fermion contributions. In the chiral limit the tricritical point (TCP) is determined analytically. The softening of the sigma particle is verified at this point and is further investigated for a physical pion mass in the neighbourhood of the critical endpoint (CEP).

hep-ph↗
arXiv2004

Analytic determination of the T-μphase diagram of the chiral quark model

Using a gap equation for the pion mass a nonperturbative method is given for solving the chiral quark-meson model in the chiral limit at the lowest order in the fermion contributions encountered in a large N_f approximation. The location of the tricritical point is analytically determined. A mean field potential is constructed from which critical exponents can be obtained.

hep-ph↗
arXiv2003

T-μphase diagram of the chiral quark model from a large flavor number expansion

The chiral phase boundary of strong matter is determined in the T-μplane from the chiral quark model, applying a non-perturbatively renormalised treatment, involving chains of pion-bubbles and 1-loop fermion contributions. In the absence of explicit symmetry breaking the second order portion of the phase boundary and the location of the tricritical point (TCP) are determined analytically. Sensitivity of the results to the renormalisation scale is carefully investigated. The softening of the sigma-pole near the second order transitions is confirmed.

hep-ph↗
arXiv2003

Universal threshold enhancement

By assuming certain analytic properties of the propagator, it is shown that universal features of the spectral function including threshold enhancement arise if a pole describing a particle at high temperature approaches in the complex energy plane the threshold position of its two-body decay with the variation of T. The case is considered, when one can disregard any other decay processes. The quality of the proposed description is demonstrated by comparing it with the detailed large N solution of the linear sigma model around the pole-threshold coincidence.

hep-ph↗
arXiv2002

Second sheet $σ$ pole and the threshold enhancement of the spectral function in the scalar-isoscalar meson-sector

The scalar-isoscalar propagator of the effective linear $σ$ model of meson dynamics is investigated with the help of an expansion in the number of the Goldstone bosons. A generic scenario is suggested for the temperature and density driven evolution of its pole in the second Riemann sheet. An extended temperature range, correlated with characteristic pole locations, is found where the phenomenon of threshold enhancement takes place in the corresponding spectral function.

hep-ph↗
arXiv2002

The scalar-isoscalar spectral function of strong matter in a large N approximation

The enhancement of the scalar-isoscalar spectral function near the two-pion threshold is studied in the framework of an effective linear $σ$ model, using a large N approximation in the number of the Goldstone bosons. The effect is rather insensitive to the detailed T=0 characteristics of the $σ$ pole, it is accounted by a pole moving with increasing $T$ along the real axis of the second Riemann sheet towards the threshold location from below.

hep-ph↗
arXiv2002

Finite temperature spectral function of the $σ$ meson from large N expansion

The spectral function of the scalar-isoscalar channel of the O(N) symmetric linear $σ$ model is studied in the broken symmetry phase. The investigation is based on the leading order evaluation of the self-energy in the limit of large number of Goldstone bosons. We describe its temperature dependent variation in the whole low temperature phase. This variation closely reflects the trajectory of the scalar-isoscalar quasiparticle pole. In the model with no explicit chiral symmetry breaking we have studied near the critical point also the corresponding dynamical exponent.

hep-ph↗
arXiv2002

Finite temperature spectral functions of the linear O(N)-model at large N applied to the $π-σ$ system

The thermal evolution of the spectral densities derivable from the two-point functions of the elementary and the quadratic composite fields of the O(N) model is studied in the isosinglet channel and in the broken symmetry phase at infinite N. The results are applied with realistic parameter values to the N=4 case. They provide a reasonable description of the $σ$ meson at T=0. Threshold enhancement is observed around $T\sim 1.07m_π$. For higher temperatures the maximum of the spectral function in the single meson channel decreases and becomes increasingly rounded.

hep-ph↗
arXiv1997

Diffusion in normal and critical transient chaos

In this paper we investigate deterministic diffusion in systems which are spatially extended in certain directions but are restricted in size and open in other directions, consequently particles can escape. We introduce besides the diffusion coefficient D on the chaotic repeller a coefficient ${\hat D}$ which measures the broadening of the distribution of trajectories during the transient chaotic motion. Both coefficients are explicitly computed for one-dimensional models, and they are found to be different in most cases. We show furthermore that a jump develops in both of the coefficients for most of the initial distributions when we approach the critical borderline where the escape rate equals the Liapunov exponent of a periodic orbit.

chao-dyn↗