Lattice QCD at Imaginary Chemical Potential in the Chiral Limit

Abstract

We report on an ongoing study on the interplay between Roberge-Weiss (RW) and chiral transitions in simulations of (2+1)-flavor QCD with an imaginary chemical potential. We established that the RW endpoint belongs to the 3-$d$, $Z_2$ universality class when calculations are done with the Highly Improved Staggered Quark (HISQ) action in the RW plane with physical quark masses. We also have explored a range of quark masses corresponding to pion mass values, $m_{\pi }\ge 40$~MeV and found that the transition is consistent with $Z_2$ universality class. We argue that observables that were usually used to determine the chiral phase transition temperature, e.g. the chiral condensate and chiral susceptibility, are sensitive to the RW transition and are energy-like observables for the $Z_2$ transition, contrary to the magnetic-like (order parameter) behavior at vanishing chemical potential. Moreover the calculations performed at $m_{\pi }\sim 40$~MeV also put a stringent constraint for a critical pion mass at zero chemical potential for a possible first-order chiral phase transition.

arXiv commentPrepared for the proceedings of LATTICE2021, MIT, USA, online

References in corpus (12)

• The chiral and deconfinement aspects of the QCD transition
• Chiral phase transition temperature in (2+1)-Flavor QCD
• Precise determination of critical exponents and equation of state by field theory methods
• On the order of the QCD chiral phase transition for different numbers of quark flavours
• The chiral phase transition in two-flavor QCD from imaginary chemical potential
• Chiral phase structure of three flavor QCD at vanishing baryon number density
• Second order cumulants of conserved charge fluctuations revisited I. Vanishing chemical potentials
• Numerical equation of state and other scaling functions from an improved three-dimensional Ising model
• Roberge-Weiss endpoint and chiral symmetry restoration in $N_f=2+1$ QCD
• Sensitivity of the Polyakov loop and related observables to chiral symmetry restoration
• Critical end points in (2+1)-flavor QCD with imaginary chemical potential
• QCD phase diagram for finite imaginary chemical potential with HISQ fermions