Lattice gauge action suppressing near-zero modes of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>H</mml:mi><mml:mi>W</mml:mi></mml:msub></mml:math>

Fukaya, Hidenori; Hashimoto, S.; Ishikawa, Ken-ichi; Kaneko, T.; Matsufuru, Hideo; Onogi, Tetsuya; Yamada, Norikazu

doi:10.1103/physrevd.74.094505

Cited by 111 publications

(132 citation statements)

References 41 publications

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“…A generation of configurations with dynamical overlap quarks requires a huge computational cost. To accelerate HMC, we introduce extra (unphysical) Wilson fermion and ghost fields, which suppress the appearance of the zero mode of H W (−m 0 ) [13]. At a price, the global topological charge Q is frozen during the HMC evolution.…”

Section: Simulation Parametersmentioning

confidence: 99%

“…This makes the dynamical overlap fermion simulation substantially more costly. In this work, we avoid this problem by introducing a topology fixing term to a gauge field action [13], with which we never encounter the discontinuity of the sign function. The physical effect of fixing the topological charge can be understood and be estimated, at a solid theoretical ground, as a finite volume effect [14].…”

Section: Introductionmentioning

confidence: 99%

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BKwith two flavors of dynamical overlap fermions

et al. 2008

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We present a two-flavor QCD calculation of B K on a 16 3 × 32 lattice at a ∼ 0.12 fm (or equivalently a −1 =1.67 GeV). Both valence and sea quarks are described by the overlap fermion formulation. The matching factor is calculated nonperturbatively with the so-called RI/MOM scheme. We find that the lattice data are well described by the next-to-leading order (NLO) partially quenched chiral perturbation theory (PQChPT) up to around a half of the strange quark mass (m phys s /2). The data at quark masses heavier than m phys s /2 are fitted including a part of next-to-next-to-leading order terms. We obtain B MS K (2 GeV) = 0.537(4)(40), where the first error is statistical and the second is an estimate of systematic uncertainties from finite volume, fixing topology, the matching factor, and the scale setting.

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Section: Simulation Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

BKwith two flavors of dynamical overlap fermions

et al. 2008

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“…(* denote values that were determined from fewer than 300 trajectories.) 3 Further, comparing m res without any weighting factor to m res at 0.01/0.10 above and below the transition: below the transition, relative suppression of m res is greater than at the transition; and above the transition, relative suppression is less than at the transition. Accordingly, this weighting factor can be expected to be increasingly effective as gauge-field coupling increases.…”

Section: Numerical Studiesmentioning

confidence: 99%

“…Fukaya (ref. [3]) demonstrated that a ratio of determinants Wilson Dirac fermions with a real numerator mass and a chirally-twisted denominator mass acts as such a weighting factor for overlap fermions.…”

mentioning

confidence: 99%

Reducing Chiral Symmetry Breaking in Domain Wall Fermions at fixed $L_s$

Renfrew¹,

Blum²,

Christ³

et al. 2009

Proceedings of the XXVI International Symposium on Lattice Field Theory — PoS(LATTICE 2008)

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At stronger gauge-field couplings, the domain wall fermion (DWF) residual mass (m res ), a measure of chiral symmetry breaking (χ SB ), grows rapidly as it is largely due to near zero fermion eigenmodes of log(T ), where T is the 4D transfer matrix along the fifth dimension. The number of these eigenmodes increase rapidly at strong coupling. To suppress such near-zero eigenmodes, we have added to the DWF path integral a multiplicative weighting factor consisting of a ratio of determinants of Wilson-Dirac fermions having a chirally twisted mass with a large negative real component and a small imaginary chiral component. Numerical results show that this weighting factor with an appropriate choice of twisted masses significantly suppresses m res while allowing adequate topological tunneling.

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“…Inspired by refs. [36,37], we tried, as an attempt, to enhance the number of configurations with nonzero Q by inserting…”

Section: Jhep10(2015)136mentioning

confidence: 99%

Topology in QCD and the axion abundance

Kitano

Yamada

2015

J. High Energ. Phys.

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The temperature dependence of the topological susceptibility in QCD, χ t , essentially determines the abundance of the QCD axion in the Universe, and is commonly estimated, based on the instanton picture, to be a certain negative power of temperature. While lattice QCD should be able to check this behavior in principle, the temperature range where lattice QCD works is rather limited in practice, because the topological charge is apt to freezes at high temperatures. In this work, two exploratory studies are presented. In the first part, we try to specify the temperature range in the quenched approximation. Since our purpose here is to estimate the range expected in unquenched QCD through quenched simulations, hybrid Monte Carlo (HMC) algorithm is employed instead of heatbath algorithm. We obtain an indication that unquenched calculations of χ t encounter the serious problem of autocorrelation already at T ∼ 2 T c or even below with the plain HMC. In the second part, we revisit the axion abundance. The absolute value and the temperature dependence of χ t in real QCD can be significantly different from that in the quenched approximation, and is not well established above the critical temperature. Motivated by this fact and precedent arguments which disagree with the conventional instanton picture, we estimate the axion abundance in an extreme case where χ t decreases much faster than the conventional power-like behavior. We find a significant enhancement of the axion abundance in such a case.

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Lattice gauge action suppressing near-zero modes ofHW

Cited by 111 publications

References 41 publications

BKwith two flavors of dynamical overlap fermions

BKwith two flavors of dynamical overlap fermions

Reducing Chiral Symmetry Breaking in Domain Wall Fermions at fixed $L_s$

Topology in QCD and the axion abundance

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