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QCD and Numerical Analysis III: Proceedings of the Third International Workshop on Numerical Analysis and Lattice QCD, Edinburgh June-July 2003

Artan Bori~i ; Andreas Frommer ; Bálint Joó ; Anthony Kennedy ; Brian Pendleton (eds.)

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Institución detectada Año de publicación Navegá Descargá Solicitá
No detectada 2005 SpringerLink

Información

Tipo de recurso:

libros

ISBN impreso

978-3-540-21257-7

ISBN electrónico

978-3-540-28504-5

Editor responsable

Springer Nature

País de edición

Reino Unido

Fecha de publicación

Información sobre derechos de publicación

© Springer-Verlag Berlin Heidelberg 2005

Tabla de contenidos

An Introduction to Lattice Chiral Fermions

Herbert Neuberger

This write-up starts by introducing lattice chirality to people possessing a fairly modern mathematical background, but little prior knowledge about modern physics. I then proceed to present two new and speculative ideas.

Palabras clave: Line Bundle; Dirac Operator; Chiral Symmetry; Weyl Fermion; Weyl Mode.

Part I - Surveys | Pp. 3-13

Computing f(A)b for Matrix Functions f

Philip I. Davies; Nicholas J. Higham

For matrix function f we investigate how to compute a matrix-vector product f ( A ) b without explicitly computing f ( A ). A general method is described that applies quadrature to the matrix version of the Cauchy integral theorem. Methods specific to the logarithm, based on quadrature, and fractional matrix powers, based on solution of an ordinary differential equation initial value problem, are also presented

Part I - Surveys | Pp. 15-24

Computational Methods for the Fermion Determinant and the Link Between Overlap and Domain Wall Fermions

Artan Boriçi

This paper reviews the most popular methods which are used in lattice QCD to compute the determinant of the lattice Dirac operator: Gaussian integral representation and noisy methods. Both of them lead naturally to matrix function problems. We review the most recent development in Krylov subspace evaluation of matrix functions. The second part of the paper reviews the formal relationship and algebraic structure of domain wall and overlap fermions. We review the multigrid algorithm to invert the overlap operator. It is described here as a preconditioned Jacobi iteration where the preconditioner is the Schur complement of a certain block of the truncated overlap matrix.

Palabras clave: Bilinear Form; Dirac Operator; Chiral Fermion; Wilson Fermion; Lanczos Algorithm.

Part I - Surveys | Pp. 25-39

Monte Carlo Simulations of Lattice QCD

Mike Peardon

This survey reviews computational methodologies in lattice gauge theory as a discretisation of QCD. We particularly focus on techniques for stochastic processes and molecular dynamics which are at the heart of modern lattice QCD simulations.

Palabras clave: Markov Process; Importance Sampling; Chiral Limit; Lattice Simulation; Link Variable.

Part I - Surveys | Pp. 41-54

Determinant and Order Statistics

Artan Boriçi

Noisy methods give in general a biased estimation of the quark determinant. In this paper we describe order statistics estimators which eliminate this bias. The method is illustrated in case of Schwinger model on the lattice.blReferences

Palabras clave: Order Statistic; Wilson Loop; Dirac Operator; Fermion Determinant; Domain Wall Fermion.

Part II - Lattice QCD | Pp. 57-66

Monte Carlo Overrelaxation for SU(N) Gauge Theories

Philippe de Forcrand; Oliver Jahn

The standard approach to Monte Carlo simulations of SU ( N ) Yang-Mills theories updates successive SU (2) subgroups of each SU ( N ) link. We follow up on an old proposal of Creutz, to perform overrelaxation in the full SU ( N ) group instead, and show that it is more efficient.

Palabras clave: Gauge Theory; Wilson Loop; String Tension; Polar Decomposition; Polyakov Loop.

Part II - Lattice QCD | Pp. 67-73

Improved Staggered Fermions

Eduardo Follana

At light quark masses, finite lattice spacing gives rise to spectrum doublers in the staggered fermion formalism, thus causing ambiguities in the extraction of physical quantities. We present results for the pion spectrum of simulations showing how improvements of the staggered fermion action remedy this deficiency.

Palabras clave: Lattice Spacing; Dynamical Quark; Light Quark Masse; Stagger Fermion; Pion Spectrum.

Part II - Lattice QCD | Pp. 75-81

Perturbative Landau Gauge Mean Link Tadpole Improvement Factors

I.T. Drummond; A. Hart; R.R. Horgan; L.C. Storoni

We calculate the two loop Landau mean links for Wilson and improved SU (3) gauge actions, using twisted boundary conditions as a gauge invariant infrared regulator. We show that these numbers accurately describe high-ß Monte Carlo simulations, and use these to infer the three loop coefficients.

Palabras clave: Loop Order; Gluon Propagator; Landau Gauge; Perturbative Series; Gauge Action.

Part II - Lattice QCD | Pp. 83-89

Reversibility and Instabilities in Hybrid Monte Carlo Simulations

Bálint Joó

It has long been known in the lattice community, that molecular dynamics (MD) integrators used in lattice QCD simulations can suffer from instabilities. In this contribution we review pedagogically where these instabilities arise, how they may be noticed and what actions can be taken to avoid them. The discussion is of relevance to simulations with light quarks such as those attainable using Ginsparg Wilson fermions.

Palabras clave: Molecular Dynamic; Light Quark; High Order Scheme; Small Step Size; Simple Harmonic Oscillator.

Part II - Lattice QCD | Pp. 91-99

A Finite Baryon Density Algorithm

Keh-Fei Liu

I will review the progress toward a finite baryon density algorithm in the canonical ensemble approach which entails particle number projection from the fermion determinant. These include an efficient Padé-Z_2 stochastic estimator of the Tr log of the fermion matrix and a Noisy Monte Carlo update to accommodate unbiased estimate of the probability. Finally, I will propose a Hybrid Noisy Monte Carlo algorithm to reduce the large fluctuation in the estimated Tr log due to the gauge field which should improve the acceptance rate. Other application such as treating u and d as two separate flavors is discussed.

Palabras clave: Partition Function; Baryon Number; Gauge Action; Quark Loop; Stagger Fermion.

Part II - Lattice QCD | Pp. 101-111