Shotaro Oka

QCD phase transition at real chemical potential with canonical approach

A bstractWe study the finite density phase transition in the lattice QCD at real chemical potential. We adopt a canonical approach and the canonical partition function is constructed for Nf = 2 QCD. After derivation of the canonical partition function we calculate observables like the pressure, the quark number density, its second cumulant and the chiral condensate as a function of the real chemical potential. We covered a wide range of temperature region starting from the confining low to the deconfining high temperature; 0.65Tc ≤ T ≤ 3.62Tc. We observe a possible signal of the deconfinement and the chiral restoration phase transition at real chemical potential below Tc starting from the confining phase. We give also the convergence range of the fugacity expansion.

Canonical approach to finite density QCD with multiple precision computation

We calculate the baryon chemical potential (

Canonical approach to the finite density QCD with winding number expansion

\mu_B

Study of the sign problem in canonical approach

) dependence of thermodynamic observables, i.e., pressure, baryon number density and susceptibility by lattice QCD using the canonical approach. We compare the results with those by the multi parameter reweighting (MPR) method; Both methods give very consistent values in the regions where errors of the MPR are under control. The canonical method gives reliable results over

Beating the sign problem in finite density lattice QCD

\mu_ B/T=3

Exploring finite density QCD phase transition with canonical approach —Power of multiple precision computation—

,with

Validity range of canonical approach to finite density QCD

T

Calculation of high-order cumulants with canonical ensemble method in lattice QCD

being temperature. Multiple precision operations play an important roll in the evaluation of canonical partition functions.

Canonical approach -- Investigation of finite density QCD phase transition

The canonical partition function is related to the grand canonical one through the fugacity expansion and is known to have no sign problem. In this paper we perform the fugacity expansion by a method of the hopping parameter expansion in temporal direction for the lattice QCD: winding number expansion. The canonical partition function is constructed for Nf=2 QCD starting from gauge configurations at zero chemical potential. After derivation of the canonical partition function we calculate hadronic observables like chiral condensate and quark number density and the pressure at the real chemical potential.

Study of high density phase transition in lattice QCD with canonical approach

It is known that the sign problem emerges as a complex phase of the canonical partition function in canonical approach. We confirmed that the origin of the complex phase is breaking of the charge conjugation with a simple model. The main purpose of this study is suppressing the complex phase even at low temperature. We realized it by increasing the number of gauge field configurations. In particular, the complex phase was suppressed less than π/2 in 1σ for NB < 7 atT = 0.81Tc