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Boriçi, Artan (University of Edinburgh)
DETERMINANT AND ORDER STATISTICS
Thursday, 03 July, 09:30
Abstract: This is a follow up of the introductory talk on the determinant computations. It describes an approximate stochastic representation of the quark determinant in terms of a certain order statistics distribution. Approximation errors are discussed and illustrated in the Monte Carlo simulation of the lattice Schwinger model.
Liu, Keh-Fei (University of Kentucky)
AN ALGORITHM FOR FINITE DENSITY
Thursday, 03 July, 11:00
Abstract: I will review the difficulty of lattice QCD simulation for finite baryon density at zero temperature and propose an algorithm in the canonical ensemble approach which projects out the baryon number in each gauge configuration. I will also discuss its potential application to odd number of flavors.
de Forcrand, Philippe (ETH Zurich and CERN)
MONTE CARLO OVERRELAXATION FOR SU(N) GAUGE THEORIES
Thursday, 03 July, 12:00
Abstract: We take a fresh look at Monte Carlo overrelaxation for the case of SU(N) Yang-Mills theories. We compare the approach of performing N(N-1)/2 microcanonical SU(2) steps with that of performing a single SU(N) step. We show that the latter strategy provides superior decorrelation for a similar amount of work.
Fleming, George (Thomas Jefferson National Accelerator Laboratory)
WHAT CAN LATTICE QCD LEARN FROM NMR SPECTROSCOPISTS
Thursday, 03 July, 14:00
Abstract: Euclidean-time hadron correlation functions computed in Lattice QCD (LQCD) are modeled by a sum of decaying exponentials, reminiscent of the exponentially damped sinusoid models of free induction decay (FID) in Nuclear Magnetic Resonance (NMR) spectroscopy. We present our initial progress in studying how data modelling techniques commonly used in NMR perform when applied to LQCD data.
Joó, Bálint (University of Edinburgh)
REVERSIBILITY AND INSTABILITY IN HMC SIMULATIONS
Thursday, 03 July, 15:30
Abstract: We review the problem of instabilities in the molecular dynamics integrators used in Hybrid Monte Carlo and other molecular dynamics based algorithms. In Hybrid Monte Carlo simulations, reversible and area preserving molecular dynamics integration schemes are needed to ensure that detailed balance is satisfied. The simplest and most frequently used scheme is the leap-frog scheme. We demonstrate the onset of instabilities in this scheme using the harmonic oscillator. We demonstrate instabilities in lattice simulations using Wilson-Clover dynamical fermions. Finally we discuss the potential effects of instabilities for inexact simulation algorithms and for exact simulations with very light quarks, the latter being what is chiefly desired from simulations using dynamical Ginsparg-Wilson Fermions. Note: This talk is meant to be pedagogical, and chiefly for the numerical analysts in the audience – as the lattice guys have heard it already, probably more than once :)
Young, Ross (University of Adelaide)
CHIRAL EFFECTIVE FIELD THEORY FOR LATTICE QCD
Thursday, 03 July, 16:15
Abstract: The extrapolation of lattice QCD simulations, performed at relatively large quark mass, to the chiral regime is a nontrivial problem. Here we demonstrate the difficulty associated with the direct application of the standard formulation of chiral perturbation theory. To overcome this difficulty, we present the implementation of a finite-range regulator (FRR) in chiral field theory. Results show that modern lattice QCD can constrain the extrapolation to minimal systematic errors. Simulations in the chiral regime are still necessary to reduce statistical errors and directly observe chiral nonanalytic behaviour.