**Location:** Cyclotron Building (434), Seminar
Room

**Friday, October 2, 4:00pm**

Min He (Cyclotron Institute Texas A&M)

"Susceptibilites and QCD chiral phase transition"

Abstract

Low energy in-vacuum QCD exhibits two remarkable

features, namely the quark confinement and the spontaneous/dynamical

chiral symmetry breaking. At sufficiently high temperature and/or

baryon density, quarks are expected to de-confine from hadrons and

probably at the same time, the broken chiral symmetry gets restored.

This is the so-called QCD phase transition that is relevant to the

evolution of very early Universe after the "Big Bang" and is being

explored via relativistic heavy ion collisions in terrestrial

laboratories (little bangs).

In this talk, we investigate some aspects of the chiral transition

by studying two susceptibilities. We derive model-independent closed

integral formulae for the chiral susceptibility and the quark-number

susceptibility, which express the latter in terms of QCD dressed

two- and three-point functions. These are then illustrated by model

calculations in the framework of Dyson-Schwinger and Bethe-Salpeter

equations. Some qualitative/quantitative characteristics concerning

QCD chiral transition are identified: 2nd/1st -order phase

transition, crossover, critical end point and phase diagram on the

T-$\mu$ plane. Comparison with results from lattice simulations and

some other phenomenological model studies will also be discussed.

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