[Paper Review] Quark-hadron phase structure, thermodynamics and magnetization of QCD matter

Abdel Nasser Tawfik, Abdel Magied Diab+1 more|arXiv (Cornell University)|Apr 26, 2016

High-Energy Particle Collisions Research3 citations

TL;DR

This study employs the SU(3) Polyakov linear-sigma model in mean-field approximation to investigate the quark-hadron phase structure, thermodynamics, and magnetization of QCD matter under finite magnetic fields. It finds inverse magnetic catalysis, with chiral transition temperatures decreasing as magnetic field strength increases, and confirms paramagnetic behavior in QCD matter, showing strong agreement with recent lattice QCD simulations across thermodynamic and magnetic properties.

ABSTRACT

SU($3$) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and magnetization of the QCD matter. In mean-field approximation, the dependence of the chiral order-parameter on finite magnetic field is also calculated. In a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, specific heat are presented and some magnetic properties are described, as well. Wherever available these results are confronted to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous result that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is to be characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization shows that the conclusion that the QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature, is confirmed, as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees-of-freedom in both hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.

Motivation & Objective

• To characterize the quark-hadron phase structure of QCD matter under finite magnetic fields.
• To determine thermodynamic quantities such as trace anomaly, speed of sound, entropy density, and specific heat in both hadronic and partonic phases.
• To analyze the magnetization and magnetic response of QCD matter, identifying paramagnetic or diamagnetic behavior.
• To compare results with recent lattice QCD simulations at finite magnetic fields and vanishing chemical potential.
• To validate the SU(3) Polyakov linear-sigma model as a reliable effective framework for describing QCD matter across the chiral and deconfinement transitions.

Proposed method

• The SU(3) Polyakov linear-sigma model (PLSM) is employed in mean-field approximation to describe both chiral and deconfinement dynamics in QCD matter.
• Landau quantization is applied to model the effects of finite magnetic fields on quark dynamics, particularly on charged quark cyclotron orbits.
• The partition function is constructed to compute thermodynamic quantities, including trace anomaly, speed of sound squared, entropy density, and specific heat.
• The chiral condensates and deconfinement order parameters are calculated as functions of temperature and magnetic field strength.
• Magnetization is derived from the free energy's dependence on the longitudinal momentum component along the magnetic field direction.
• Results are benchmarked against recent lattice QCD simulations at zero chemical potential and finite magnetic fields.

Experimental results

Research questions

• RQ1 How does a finite magnetic field affect the chiral and deconfinement phase transitions in QCD matter?
• RQ2 What is the temperature and magnetic field dependence of key thermodynamic quantities such as trace anomaly, speed of sound, entropy, and specific heat?
• RQ3 Does QCD matter exhibit paramagnetic or diamagnetic behavior, and how does this depend on temperature and magnetic field?
• RQ4 To what extent does the SU(3) PLSM reproduce lattice QCD results for thermodynamic and magnetic properties at finite magnetic fields?
• RQ5 How does the magnetic field influence the restoration of chiral symmetry and the suppression of quark condensates?

Key findings

• The chiral pseudo-critical temperature decreases with increasing magnetic field strength, indicating inverse magnetic catalysis.
• The light-quark chiral transition temperature decreases faster than the strange-quark transition temperature with rising magnetic field.
• The PLSM results for chiral condensates and deconfinement order parameters show excellent agreement with recent lattice QCD simulations at zero chemical potential.
• The magnetization is positive slightly below and far above the pseudo-critical temperature, confirming paramagnetic behavior of QCD matter.
• Thermodynamic quantities such as trace anomaly, entropy density, and specific heat are enhanced at finite magnetic fields, especially in the hadronic phase.
• The quark-hadron phase boundary shifts to lower temperatures with increasing magnetic field, consistent with lattice QCD findings.