Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kanamori, Issaku*; Kaneko, Takashi*; Nakamura, Yoshifumi*; Rohrhofer, C.*; Suzuki, Kei
Proceedings of Science (Internet), 396, p.332_1 - 332_7, 2022/07
The axial U(1) anomaly in high-temperature QCD plays an important role to understand the phase diagram of QCD. The previous works by JLQCD Collaboration studied high-temperature QCD using 2-flavor dynamical chiral fermions such as the domain-wall fermion and reweighted overlap fermion. We extend our simulations to QCD with 2+1-flavor dynamical quarks, where the masses of the up, down, and strange quarks are near the physical point, and the temperatures are close to or higher than the pseudocritical temperature. In this talk, we will present the results for the Dirac spectrum, topological susceptibility, axial U(1) susceptibility, and hadronic collelators.
Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*; Suzuki, Kei
Proceedings of Science (Internet), 396, p.050_1 - 050_9, 2022/07
In the early days of QCD, the axial anomaly was considered as a trigger for the breaking of the
symmetry through topological excitations of gluon fields. However, it has been a challenge for lattice QCD to quantify the effect. In this work, we simulate QCD at high temperatures with chiral fermions. The exact chiral symmetry enables us to separate the contribution from the axial
breaking from others among the susceptibilities in the scalar and pseudoscalar channels. Our result in two-flavor QCD indicates that the chiral susceptibility, which is conventionally used as a probe for
breaking, is actually dominated by the axial
breaking at temperatures
MeV.
Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*; Suzuki, Kei
Progress of Theoretical and Experimental Physics (Internet), 2022(2), p.023B05_1 - 023B05_12, 2022/02
Times Cited Count:8 Percentile:81.55(Physics, Multidisciplinary)The chiral susceptibility, or the first derivative of the chiral condensate with respect to the quark mass, is often used as a probe for the QCD phase transition since the chiral condensate is an order parameter of symmetry breaking. However, the chiral condensate also breaks the axial
symmetry, which is usually not studied as it is already broken by the anomaly and apparently has little impact on the transition. We investigate the susceptibilities in the scalar and pseudoscalar channels in order to quantify how much the axial
breaking contributes to the chiral phase transition. Employing a chirally symmetric lattice Dirac operator and its eigenmode decomposition, we separate the axial
breaking effects from others. Our result in two-flavor QCD indicates that both of the connected and disconnected chiral susceptibilities are dominated by axial
breaking at temperatures
MeV after the quadratically divergent constant is subtracted.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physical Review D, 104(9), p.094515_1 - 094515_11, 2021/11
Times Cited Count:5 Percentile:42.69(Astronomy & Astrophysics)We investigate the Kondo effect with Wilson fermions. This is based on a mean-field approach for the chiral Gross-Neveu model including four-point interactions between a light Wilson fermion and a heavy fermion. For massless Wilson fermions, we demonstrate the appearance of the Kondo effect. We point out that there is a coexistence phase with both the light-fermion scalar condensate and Kondo condensate, and the critical chemical potentials of the scalar condensate are shifted by the Kondo effect. For negative-mass Wilson fermions, we find that the Kondo effect is favored near the parameter region realizing the Aoki phase. Our findings will be useful for understanding the roles of heavy impurities in Dirac semimetals, topological insulators, and lattice simulations.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physical Review Research (Internet), 3(2), p.023201_1 - 023201_23, 2021/06
The Casimir effect arises from the zero-point energy of particles in momentum space deformed by the existence of two parallel plates. For degrees of freedom on the lattice, its energy-momentum dispersion is determined so as to keep a periodicity within the Brillouin zone, so that its Casimir effect is modified. We study the properties of Casimir effect for lattice fermions, such as the naive fermion, Wilson fermion, and overlap fermion based on the Mbius domain-wall fermion formulation, in the
,
, and
dimensional spacetime with the periodic or antiperiodic boundary condition. An oscillatory behavior of Casimir energy between odd and even lattice size is induced by the contribution of ultraviolet-momentum (doubler) modes, which realizes in the naive fermion, Wilson fermion in a negative mass, and overlap fermions with a large domain-wall height. Our findings can be experimentally observed in condensed matter systems such as topological insulators and also numerically measured in lattice simulations.
Aoki, Shinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kaneko, Takashi*; Rohrhofer, C.*; Suzuki, Kei
Physical Review D, 103(7), p.074506_1 - 074506_18, 2021/04
Times Cited Count:14 Percentile:76.78(Astronomy & Astrophysics)We investigate the axial anomaly of two-flavor QCD at temperatures 190-330 MeV. In order to preserve precise chiral symmetry on the lattice, we employ the M
bius domain-wall fermion action as well as overlap fermion action implemented with a stochastic reweighting technique. Compared to our previous studies, we reduce the lattice spacing to 0.07 fm, simulate larger multiple volumes to estimate finite size effect, and take more than four quark mass points, including one below physical point to investigate the chiral limit. We measure the topological susceptibility, axial
susceptibility, and examine the degeneracy of
partners in meson/baryon correlators. All the data above the critical temperature indicate that the axial
violation is consistent with zero within statistical errors. The quark mass dependence suggests disappearance of the
anomaly at a rate comparable to that of the
symmetry breaking.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physics Letters B, 809, p.135713_1 - 135713_7, 2020/10
Times Cited Count:10 Percentile:75.41(Astronomy & Astrophysics)We propose a definition of the Casimir energy for free lattice fermions. From this definition, we study the Casimir effects for the massless or massive naive fermion, Wilson fermion, and (Mbius) domain-wall fermion in 1+1 dimensional spacetime with the spatial periodic or antiperiodic boundary condition. For the naive fermion, we find an oscillatory behavior of the Casimir energy, which is caused by the difference between odd and even lattice sizes. For the Wilson fermion, in the small lattice size of
, the Casimir energy agrees very well with that of the continuum theory, which suggests that we can control the discretization artifacts for the Casimir effect measured in lattice simulations. We also investigate the dependence on the parameters tunable in M
bius domain-wall fermions. Our findings will be observed both in condensed matter systems and in lattice simulations with a small size.
Rohrhofer, C.*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Gattringer, C.*; Glozman, L. Ya.*; Hashimoto, Shoji*; Lang, C. B.*; Suzuki, Kei
Proceedings of Science (Internet), 363, p.227_1 - 227_7, 2020/08
Properties of QCD matter change significantly around the chiral crossover temperature, and the effects on and topological susceptibilities, as well as the meson spectrum have been studied with much care. Baryons and the effect of parity doubling in this temperature range have been analyzed previously by various other groups employing different setups. Here we construct suitable operators to investigate chiral and axial
symmetries in the baryon spectrum. Measurements for different volumes and quark-masses are done with two flavors of chirally symmetric domain-wall fermions at temperatures above the critical one. The possibility of emergent
and
symmetries is discussed.
Suzuki, Kei; Aoki, Shinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*
Proceedings of Science (Internet), 363, p.178_1 - 178_7, 2020/08
We investigate the high-temperature phase of QCD using lattice QCD simulations with dynamical M
bius domain-wall fermions. On generated configurations, we study the axial
symmetry, overlap-Dirac spectra, screening masses from mesonic correlators, and topological susceptibility. We find that some of the observables are quite sensitive to lattice artifacts due to a small violation of the chiral symmetry. For those observables, we reweight the M
bius domain-wall fermion determinant by that of the overlap fermion. We also check the volume dependence of observables. Our data near the chiral limit indicates a strong suppression of the axial
anomaly at temperatures
220 MeV.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suenaga, Daiki*; Suzuki, Kei
Physical Review D, 100(3), p.034016_1 - 034016_14, 2019/08
Times Cited Count:5 Percentile:30.13(Astronomy & Astrophysics)We propose mesons as probes to investigate finite-volume effects for chiral symmetry breaking at zero and finite temperatures. By using the 2+1-flavor linear sigma model with constituent light quarks, we analyze the Casimir effects for the
mean fields; the chiral symmetry is rapidly restored by the antiperiodic boundary for light quarks, and the chiral symmetry breaking is catalyzed by the periodic boundary. We also show the phase diagram of the
mean fields on the volume and temperature plane. For
mesons, we employ an effective model based on the chiral-partner structure, in which the volume dependence of
mesons is induced by the
mean fields. We find that
mesons are less sensitive to finite volume than
mesons, which is caused by the insensitivity of
mean fields. An anomalous mass shift of
mesons at high temperature with the periodic boundary will be useful in examinations with lattice QCD simulations. The dependence on the number of compactified spatial dimensions is also studied.
Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kanamori, Issaku*; Kaneko, Takashi*; Nakamura, Yoshifumi*; Rohrhofer, C.*; Suzuki, Kei; Ward, D.*
no journal, ,
no abstracts in English
Suzuki, Kei; Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suenaga, Daiki*
no journal, ,
D mesons are expected to be clear probes of the chiral condensate. For the Casimir effect in the QCD vacuum, non-perturbative properties of the QCD vacuum are modified by the volume size and boundary conditions. In this talk, we focus on the modification of the chiral symmetry breaking by the Casimir effect and the response of D mesons. By using an effective Lagrangian based on chiral partner structures for D mesons, we discuss the dependences on volume, boundary, and temperature, and the applications to lattice QCD simulations.
Suzuki, Kei
no journal, ,
In this talk, using lattice QCD simulations with dynamical fermions by JLQCD Collaboration, I will show our recent results of the observables in the high-temperature phase in which the chiral symmetry is restored, such as the axial
symmetry, topological charge, Dirac eigenvalue spectra, meson correlators, and screening masses. Our gauge ensembles are generated with Moebius domain-wall fermions, but the measurements such as susceptibilities are reweighted to those for the overlap fermions by using overlap/domain-wall reweighting technique. We find that the
and topological susceptibilities are strongly suppressed in the small quark mass region. We will also discuss the relation between the susceptibilities and meson correlators.
Suzuki, Kei
no journal, ,
D mesons are expected to be clear probes of the chiral condensate. For the Casimir effect in the QCD vacuum, non-perturbative properties of the QCD vacuum are modified by the volume size and boundary conditions. In this talk, we focus on the modification of the chiral symmetry breaking by the Casimir effect and the response of D mesons. By using an effective Lagrangian based on chiral partner structures for D mesons, we discuss the dependences on volume, boundary, and temperature, and the applications to lattice QCD simulations.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
no journal, ,
We propose a definition of the Casimir energy for free lattice fermions. From this definition, we study the Casimir effects for the massless or massive naive fermion, Wilson fermion, and (Mbius) domain-wall fermion in
dimensional spacetime with the spatial periodic or antiperiodic boundary condition. For the naive fermion, we find an oscillatory behavior of the Casimir energy, which is caused by the difference between odd and even lattice sizes. For the Wilson fermion, in the small lattice size of
, the Casimir energy agrees very well with that of the continuum theory, which suggests that we can control the discretization artifacts for the Casimir effect measured in lattice simulations. We also investigate the dependence on the parameters tunable in M
bius domain-wall fermions. Our findings will be observed both in condensed matter systems and in lattice simulations with a small size.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
no journal, ,
no abstracts in English
Suzuki, Kei
no journal, ,
The axial U(1) anomaly in high-temperature QCD plays an important role to understand the phase diagram of QCD. JLQCD Collaboration is studying high-temperature QCD using dynamical chiral fermions such as the domain-wall fermion and reweighted overlap fermion. In this talk, we will present the results for the Dirac spectrum, topological susceptibility, axial U(1) susceptibility, and hadronic collelators.
Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kanamori, Issaku*; Kaneko, Takashi*; Nakamura, Yoshifumi*; Rohrhofer, C.*; Suzuki, Kei; Ward, D.*
no journal, ,
Quantum chromodynamics (QCD) is the fundamental theory describing the dynamics of quarks and gluons. The axial U(1) symmetry in QCD is broken at low temperatures by the effect of quantum anomaly, and it is important for understanding the phase structure of QCD to investigate what happens to this symmetry in the high-temperature regime of QCD. In this study, we simulate a high-temperature regime of 2+1 flavor QCD using dynamical chiral fermions such as the domain-wall fermions and the overlap fermions (obtained by the reweighting method). Here, for up- and down-quark masses, we investigate masses heavier than the physical point, near the physical point, and lighter than the physical point. For temperatures, we investigate the near-pseudo-critical temperature and slightly lower and higher temperature regions. For physical quantities, we report results and discussion on the behavior of the Dirac spectrum, axial U(1) susceptibility, topological susceptibility, and hadronic correlation functions.