Exploring Nf=2+1 QCD thermodynamics from the gradient flow

Yusuke Taniguchi, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda, and Naoki Wakabayashi (WHOT-QCD Collaboration)
Phys. Rev. D 96, 014509 – Published 20 July 2017; Erratum Phys. Rev. D 99, 059904 (2019)

Abstract

The energy-momentum tensor plays an important role in QCD thermodynamics. Its expectation value contains information of the pressure and the energy density as its diagonal part. Further properties like viscosity and specific heat can be extracted from its correlation function. A nonperturbative evaluation of it on the lattice is called. Recently, a new method based on the gradient flow was introduced to calculate the energy-momentum tensor on the lattice and has been successfully applied to quenched QCD. In this paper, we apply the gradient flow method to calculate the energy-momentum tensor in (2+1)-flavor QCD adopting a nonperturbatively O(a)-improved Wilson quark action and the renormalization group-improved Iwasaki gauge action. As the first application of the method with dynamical quarks, we study at a single but fine lattice spacing a0.07fm with heavy u and d quarks (mπ/mρ0.63) and approximately physical s quark (mηss/mϕ0.74). With the fixed-scale approach, temperature is varied by the temporal lattice size Nt at a fixed lattice spacing. Performing simulations on lattices with Nt=16 to 4, the temperature range of T174697MeV is covered. We find that the results of the pressure and the energy density by the gradient flow method are consistent with the previous results using the T-integration method at T280MeV (Nt10), while the results show disagreement at T350MeV (Nt8), presumably due to the small-Nt lattice artifact of O((aT)2)=O(1/Nt2). We also apply the gradient flow method to evaluate the chiral condensate taking advantage of the gradient flow method that renormalized quantities can be directly computed avoiding the difficulty of explicit chiral violation with lattice quarks. We compute the renormalized chiral condensate in the MS¯ scheme at renormalization scale μ=2GeV with a high precision to study the temperature dependence of the chiral condensate and its disconnected susceptibility. Even with the Wilson-type quark action which violates the chiral symmetry explicitly, we obtain the chiral condensate and its disconnected susceptibility showing a clear signal of pseudocritical temperature at T190MeV related to the chiral restoration crossover.

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  • Received 9 November 2016

DOI:https://doi.org/10.1103/PhysRevD.96.014509

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Particles & Fields

Erratum

Erratum: Exploring Nf=2+1 QCD thermodynamics from the gradient flow [Phys. Rev. D 96, 014509 (2017)]

Yusuke Taniguchi, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda, and Naoki Wakabayashi (WHOT-QCD Collaboration)
Phys. Rev. D 99, 059904 (2019)

Authors & Affiliations

Yusuke Taniguchi1,*, Shinji Ejiri2,†, Ryo Iwami3,‡, Kazuyuki Kanaya4,§, Masakiyo Kitazawa5,6,∥, Hiroshi Suzuki7,¶, Takashi Umeda8,**, and Naoki Wakabayashi3,†† (WHOT-QCD Collaboration)

  • 1Center for Computational Sciences (CCS), University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
  • 2Department of Physics, Niigata University, Niigata 950-2181, Japan
  • 3Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
  • 4Center for Integrated Research in Fundamental Science and Engineering (CiRfSE), University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
  • 5Department of Physics, Osaka University, Osaka 560-0043, Japan
  • 6J-PARC Branch, KEK Theory Center, Institute of Particle and Nuclear Studies, KEK, 203-1, Shirakata, Tokai, Ibaraki 319-1106, Japan
  • 7Department of Physics, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
  • 8Graduate School of Education, Hiroshima University, Higashihiroshima, Hiroshima 739-8524, Japan

  • *Corresponding author. tanigchi@het.ph.tsukuba.ac.jp
  • ejiri@muse.sc.niigata-u.ac.jp
  • iwami@muse.sc.niigata-u.ac.jp
  • §kanaya@ccs.tsukuba.ac.jp
  • kitazawa@phys.sci.osaka-u.ac.jp
  • hsuzuki@phys.kyushu-u.ac.jp
  • **tumeda@hiroshima-u.ac.jp
  • ††wakabayashi@muse.sc.niigata-u.ac.jp

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Vol. 96, Iss. 1 — 1 July 2017

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