学際大規模情報基盤共同利用・共同研究拠点 (JHPCN) 公募型共同研究 2020 年度採択課題
jh200010-NAH

有限温度量子色力学のダイナミクス鈴木博

九州大学

1223Disconnected chiral susceptibility (preliminary):
0.00014
ud chiral susceptibility

Hiroshi Suzuki , Kazuyuki Kanaya , Yusuke Taniguchi , Shinji Ejiri ,45 1
2Takashi Umeda , Masakiyo Kitazawa ( Kyushu U., U. Tsukuba,
345Niigata U., Hiroshima U., Osaka U.) [WHOT-QCD Collaboration]

0.00012chi2/dof<0.1
u quark 1 loop µ0s chiral susceptibility

To understand the state of matter at very high temperature and/or0.0001
density, such as in the early universe, inside the neutron star, and in-5
8x10
the heavy ion collision etc., it is crucial to know the Equation of6x10-5
State (EoS) of Quantum Chromo Dynamics (QCD), the fundamental-5
4x10
theory of strong interactions. The ultimate goal of our project is to2x10-5
determine the EoS in the continuum by numerical simulations on the0050 100 150 200 250 300 350
basis of lattice QCD with the Wilson-type quark action. For this, weT (MeV)
are employing the energy–momentum tensor (EMT) and otherFigure:Disconnectedchiralsusceptibility
oftheudquarks(intheMS-scheme
physical quantities defined by the gradient flow (GF) and the Small
6at µ = 2 GeV in GeV )Flow-time eXpansion (SFtX) method. We summarize achievements
we made so far by utilizing the present and past JHPCN (and other)
0.00014chi2/dof<0.1
computational resources.
s quark 1 loop µ00.000120.0001(e+p)/T4

In this poster, we present the results for the Nf = 2 + 1 QCD with8x10-5
physical quark masses
6x10-5[Kanaya–Baba–Suzuki–Ejiri–Kitazawa–H.S.–Taniguchi–Umeda, PoS
4x10-5
LATTICE2019, 088 (2019) and ongoing study]. We use gauge field-52x10
configurations generated by non-perturbatively O(a)-improved Wilson
0050 100 150 200 250 300 350
quark action and the RG improved Iwasaki gauge action. The lattice
T (MeV)
spacing is fixed to a0.09 fm. T = 0 configurations are PACS-CS
3Figure: Disconnected chiral susceptibility of the s quark (in the MS-scheme
configuration on a 32 × 64 lattice. T > 0 configurations are6atµ=2GeVinGeV)
3WHOT-QCD configurations (32 × Nt, Nt = 4, 5, . . . , 18) and ourown configurations.
To reduce the statistical error in the results at T = 122 MeV, atemperature close to the pseudo-critical temperature, we
EoS obtained by SFtX method (preliminary):3
accumulated 213 new gauge configuration on a lattice 32 × 18 by
25using a JHPCN computational resources allocated to us in the fiscal
2chi /dof<0.01year 2019 (64 · 9 node · month CPU time of ITO subsystem A at1 loop µ020Research Institute for Information Technology, Kyushu University).
15We are now computing various physical quantities by using these
newly-obtained gauge configurations.

1050050100150200250300

350

T (MeV)

Figure: Entropy density (ϵ + p)/T 4 as function of temperature T
252chi /dof<0.01
1 loop µ020(e-3p)/T415
1050-5050100

150

200

250300350

T (MeV)

Figure: Trace anomaly (ϵ − 3p)/T 4 as function of temperature T

This fiscal year, 40, 000 node · hour CPU time of ITO subsystem A at
Research Institute for Information Technology, Kyushu University, wasallocated to us from the JHPCN project.
We are now generating new QCD gauge field configurations withphysical quark masses at finite temperatures to use the PACS10
configurations [Ishikawa–Ishizuka–Kuramashi–Nakamura–Namekawa–
Taniguchi–Ukita–Yamazaki–Yoshié, PRD 99, 014504 (2019)] with thelattice spacing a = 0.08 fm on a 1284 lattice as zero temperaturegauge configurations.
By using 64 nodes of the ITO subsystem A, by the hybridMonte-Carlo method, we are now generating gauge field3
configurations on a 48 × 12 lattice with the latticespacing a = 0.08 fm; this setup corresponds to thetemperature 206 MeV.

As the following Monte-Carlo history of the plaquette variableindicates we are still far way from the thermal equilibrium (i.e., thegauge configurations are not yet distributed according to the desired
Boltzmann weight). It seems that at least additional one month isneeded to achieve the thermal equilibrium.

Figure: Monte-Carlo history of the plaquette variable

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