The chiral phase transition for two-flavour QCD at imaginary and zero chemical potential

Bonati, Claudio; de Forcrand, Philippe; D'Elia, Massimo; Sanfilippo, Francesco; Philipsen, Owe

doi:10.22323/1.187.0219

Article
Report number	arXiv:1311.0473 ; CERN-PH-TH-2013-257 ; CERN-PH-TH-2013-257
Title	The chiral phase transition for two-flavour QCD at imaginary and zero chemical potential
Author(s)	Bonati, Claudio (INFN, Pisa ; Pisa U.) ; D'Elia, Massimo (INFN, Pisa ; Pisa U.) ; de Forcrand, Philippe (Zurich, ETH ; CERN) ; Philipsen, Owe (Frankfurt U.) ; Sanfilippo, Francesco (Orsay, LPT ; INFN, Rome)
Publication	2014
Imprint	03 Nov 2013
Number of pages	7 p, 7
Note	Comments: 7 p., 5 figures, contribution to 31st International Symposium on Lattice Field Theory - LATTICE 2013, July 29 - August 3, 2013, Mainz, Germany 7 p., 5 figures, contribution to 31st International Symposium on Lattice Field Theory - LATTICE 2013, July 29 - August 3, 2013, Mainz, Germany
In:	PoS LATTICE 2013 (2013) 219
In:	31st International Symposium on Lattice Field Theory, Mainz, Germany, 29 Jul - 03 Aug 2013, pp.219
DOI	10.22323/1.187.0219
Subject category	Particle Physics - Lattice
Abstract	The chiral symmetry of QCD with two massless quark flavours gets restored in a non-analytic chiral phase transition at finite temperature and zero density. Whether this is a first-order or a second-order transition has not yet been determined unambiguously, due to the difficulties of simulating light quarks. We investigate the nature of the chiral transition as a function of quark mass and imaginary chemical potential, using staggered fermions on N_t=4 lattices. At sufficiently large imaginary chemical potential, a clear signal for a first-order transition is obtained for small masses, which weakens with decreasing imaginary chemical potential. The second-order critical line m_c(mu_i), which marks the boundary between first-order and crossover behaviour, extrapolates to a finite m_c(mu_i=0) with known critical exponents. This implies a definitely first-order transition in the chiral limit on relatively coarse, N_t=4 lattices.
Copyright/License	Preprint: © 2013-2025 CERN (License: CC-BY-3.0)

$({\em Left}) Schematic phase transition behaviour of $N_f=2+1$ QCD for different choices of quark masses $(m_{u,d},m_s)$ at $\mu=0$. ({\em Right}) The same with chemical potential $\mu$ for quark number as an additional parameter. The critical boundary lines sweep out surfaces as $\mu$ is turned on. At imaginary chemical potential $\mu=i\pi/3 T$, the critical surfaces terminate in tricritical lines, which determines their curvature through critical scaling.$ $({\em Left}) Schematic phase transition behaviour of $N_f=2+1$ QCD for different choices of quark masses $(m_{u,d},m_s)$ at $\mu=0$. ({\em Right}) The same with chemical potential $\mu$ for quark number as an additional parameter. The critical boundary lines sweep out surfaces as $\mu$ is turned on. At imaginary chemical potential $\mu=i\pi/3 T$, the critical surfaces terminate in tricritical lines, which determines their curvature through critical scaling.$ $({\em Left}) Possible scenarios for the chiral phase transition as function of small pion mass.\\ ({\em Right)} Chiral extrapolation of the pseudo-critical temperature for twisted mass Wilson fermions \cite{tmft}.$ Show more plots

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Record created 2013-11-05, last modified 2023-03-12

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