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We consider a recent proposal by Horv\'ath {\em et al.} to address the question whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the…

High Energy Physics - Lattice · Physics 2014-11-17 Robert G. Edwards , Urs M. Heller

We study the topological properties of full QCD with four flavours of dynamical staggered fermions. In particular the topological susceptibility is measured and the problem of the determination of its first derivative is discussed.

High Energy Physics - Lattice · Physics 2015-06-25 B. Alles , M. D'Elia , A. Di Giacomo

We calculate the nucleon isovector scalar charge in lattice QCD using overlap fermions on five ensembles of gauge configurations generated by the RBC/UKQCD collaboration using the domain-wall quark action with $2+1$ dynamical flavors. The…

High Energy Physics - Lattice · Physics 2021-11-16 Liuming Liu , Ting Chen , Terrence Draper , Jian Liang , Keh-Fei Liu , Gen Wang , Yi-Bo Yang

Overlap fermions are a powerful tool for investigating the chiral and topological structure of the vacuum and the thermal states of QCD. We study various chiral and topological aspects of the finite temperature phase transition of N_f=2…

High Energy Physics - Lattice · Physics 2007-05-23 V. Weinberg , E. -M. Ilgenfritz , K. Koller , Y. Koma , G. Schierholz , T. Streuer

We introduce and compare three different Monte Carlo determinantal algorithms that allow one to compute dynamical quantities, such as the self-energy, of fermionic systems in their thermodynamic limit. We show that the most efficient…

Strongly Correlated Electrons · Physics 2018-02-14 Alice Moutenet , Wei Wu , Michel Ferrero

A scheme for separating the high- and low-frequency molecular dynamics modes in Hybrid Monte Carlo (HMC) simulations of gauge theories with dynamical fermions is presented. The algorithm is tested in the Schwinger model with Wilson…

High Energy Physics - Lattice · Physics 2019-08-14 Mike Peardon , James Sexton

We discuss a Lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like…

High Energy Physics - Lattice · Physics 2013-01-15 Krzysztof Cichy , Vincent Drach , Elena Garcia-Ramos , Gregorio Herdoiza , Karl Jansen

We present the results of an exploratory numerical study of two dimensional QCD with overlap fermions. We have performed extensive simulations for U(N_c) and SU(N_c) color groups with N_c=2, 3, 4 and coupling constants chosen to satisfy the…

High Energy Physics - Lattice · Physics 2009-11-07 F. Berruto , L. Giusti , C. Hoelbling , C. Rebbi

In the previous paper we developed a strong-coupling expansion for the lattice QCD with the overlap fermions and showed that L\"usher's "extended" chiral symmetry is spontaneously broken in some parameter region of the overlap fermions. In…

High Energy Physics - Lattice · Physics 2007-05-23 Ikuo Ichinose , Keiichi Nagao

We present a systematic comparison of various iterative methods to obtain the fermion propagator with both overlap and twisted mass fermions at fixed pion mass in the quenched approximation. Taking the best available algorithm in each case…

High Energy Physics - Lattice · Physics 2009-11-10 T. Chiarappa , K. Jansen , K. -I. Nagai , M. Papinutto , L. Scorzato , A. Shindler , C. Urbach , U. Wenger , I. Wetzorke

The overlap Dirac operator, which satisfies the Ginsparg-Wilson relation, realizes exact chiral symmetry on the lattice without any unphysical doubler modes. To perform the path integrals, one should, however, note that the overlap fermion…

High Energy Physics - Lattice · Physics 2007-05-23 Hidenori Fukaya

Overlap fermions are particularly well suited to study the finite temperature dynamics of the chiral symmetry restoration transition of QCD, which might be just an analytic crossover. Using gauge field configurations on a 24^3x10 lattice…

High Energy Physics - Lattice · Physics 2008-11-26 V. Weinberg , E. -M. Ilgenfritz , K. Koller , Y. Koma , Y. Nakamura , G. Schierholz , T. Streuer

We present a polynomial Hybrid Monte Carlo (PHMC) algorithm as an exact simulation algorithm with dynamical Kogut-Susskind fermions. The algorithm uses a Hermitian polynomial approximation for the fractional power of the KS fermion matrix.…

We demonstrate that substantial progress can be achieved in the study of the phase structure of 4-dimensional compact QED by a joint use of hybrid Monte Carlo and multicanonical algorithms, through an efficient parallel implementation. This…

High Energy Physics - Lattice · Physics 2015-06-25 G. Arnold , Th. Lippert , K. Schilling

We generalize overlap fermion by Narayanan and Neuberger by introducing a hopping parameter t. This lattice fermion has desirable properties as the original overlap fermion. We expand "Dirac" operator of this fermion in powers of t.…

High Energy Physics - Lattice · Physics 2009-10-31 Ikuo Ichinose , Keiichi Nagao

As computing resources are limited, choosing the parameters for a full Lattice QCD simulation always amounts to a compromise between the competing objectives of a lattice spacing as small, quarks as light, and a volume as large as possible.…

High Energy Physics - Lattice · Physics 2009-11-11 B. Orth , Th. Lippert , K. Schilling

I present one-loop perturbative calculations of matching coefficients between matrix elements in continuum regulated QCD and lattice QCD with overlap fermions, with emphasis a recently-proposed variant discretization of the overlap. These…

High Energy Physics - Lattice · Physics 2016-09-01 Thomas DeGrand

We introduce a dynamical fermion algorithm which is based on the hybrid Monte Carlo (HMC) algorithm, but without pseudofermions. The molecular dynamics steps in HMC are retained except the derivatives with respect to the gauge fields are…

High Energy Physics - Lattice · Physics 2009-10-28 K. F. Liu , S. J. Dong , C. Thron

We investigate the properties of the Hybrid Monte-Carlo algorithm (HMC) in high dimensions. HMC develops a Markov chain reversible w.r.t. a given target distribution $\Pi$ by using separable Hamiltonian dynamics with potential $-\log\Pi$.…

A number of proposed extensions of the Standard Model include new strongly interacting dynamics, in the form of SU(N) gauge fields coupled to various numbers of fermions. Often, these extensions allow N = 3 as a plausible choice, or even…

High Energy Physics - Phenomenology · Physics 2025-10-09 Thomas DeGrand , Ethan T. Neil