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We use low lying eigenvectors of the overlap-Dirac operator as a probe of the QCD vacuum. If instantons play a significant role one would expect the low lying eigenmodes of the overlap-Dirac operator to consist mainly of the mixed ``would…

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

The quenched approximation for QCD is, at present and in the foreseeable future, unavoidable in lattice calculations with realistic choices of the lattice spacing, volume and quark masses. In this talk, I review an analytic study of the…

High Energy Physics - Lattice · Physics 2015-06-25 Maarten F. L. Golterman

We examine quenched chiral logarithms in lattice QCD with overlap Dirac quark. For 100 gauge configurations generated with the Wilson gauge action at $ \beta = 5.8 $ on the $ 8^3 \times 24 $ lattice, we compute quenched quark propagators…

High Energy Physics - Lattice · Physics 2011-02-16 Ting-Wai Chiu , Tung-Han Hsieh

Chiral properties of QCD formulated with the domain-wall fermion (DWQCD) are studied using the anomalous quark mass m_{5q} and the spectrum of the 4-dimensional Wilson-Dirac operator. Numerical simulations are made with the standard…

Random Matrix Theory has been a unifying approach in physics and mathematics.In these lectures we discuss applications of Random Matrix Theory to QCD and emphasize underlying integrable structures. In the first lecture we give an overview…

High Energy Physics - Theory · Physics 2007-05-23 J. J. M. Verbaarschot

We investigate and clarify the role of topology and the issues surrounding the epsilon regime for staggered quarks. We study unimproved and improved staggered quark Dirac operators on quenched lattice QCD gluon backgrounds generated using a…

High Energy Physics - Lattice · Physics 2009-11-11 E. Follana , A. Hart , C. T. H. Davies , Q. Mason

We have calculated complete spectra of the staggered Dirac operator on the lattice in quenched SU(3) gauge theory for \beta = 5.4 and various lattice sizes. The microscopic spectral density, the distribution of the smallest eigenvalue, and…

High Energy Physics - Lattice · Physics 2008-11-26 M. Göckeler , H. Hehl , P. E. L. Rakow , A. Schäfer , T. Wettig

Based on the exact relationship to Random Matrix Theory, we derive the probability distribution of the k-th smallest Dirac operator eigenvalue in the microscopic finite-volume scaling regime of QCD and related gauge theories.

High Energy Physics - Theory · Physics 2009-10-31 P. H. Damgaard , S. M. Nishigaki

It has been a big challenge for lattice QCD to simulate dynamical quarks near the chiral limit. Theoretically, it is well-known that the naive chiral symmetry cannot be realized on the lattice (the Nielsen-Ninomiya theorem). Also…

High Energy Physics - Lattice · Physics 2017-08-23 Hidenori Fukaya

We analyze the eigenvalue spectrum of the staggered Dirac matrix in two-color QCD at nonzero baryon density when the eigenvalues become complex. The quasi-zero modes and their role for chiral symmetry breaking and the deconfinement…

High Energy Physics - Lattice · Physics 2009-10-31 Elmar Bittner , Maria-Paola Lombardo , Harald Markum , Rainer Pullirsch

In the epsilon-regime of lattice QCD one can get an accurate measurement of the pion decay constant F_pi by monitoring how just one single Dirac operator eigenvalue splits into two when subjected to two different external vector sources.…

High Energy Physics - Lattice · Physics 2008-11-26 G. Akemann , P. H. Damgaard

In the first part of these lectures we discuss the infrared limit of the spectrum of the QCD Dirac operator. We discuss the global symmetries of the QCD partition function and show that the Dirac spectrum near zero virtuality is determined…

High Energy Physics - Phenomenology · Physics 2007-05-23 J. J. M. Verbaarschot

The microscopic spectral eigenvalue correlations of QCD Dirac operators in the presence of dynamical fermions are calculated within the framework of Random Matrix Theory (RMT). Our approach treats the low--energy correlation functions of…

High Energy Physics - Lattice · Physics 2008-11-26 G. Akemann , E. Kanzieper

A distinctive feature of the presence of spontaneous chiral symmetry breaking in QCD is the condensation of low modes of the Dirac operator near the origin. The rate of condensation must be equal to the slope of (Mpi^2 Fpi^2)/2 with respect…

High Energy Physics - Phenomenology · Physics 2015-03-25 Georg P. Engel , Leonardo Giusti , Stefano Lottini , Rainer Sommer

Using an integration formula recently derived by Conrey, Farmer and Zirnbauer, we calculate the expectation value of the phase factor of the fermion determinant for the staggered lattice QCD action in one dimension. We show that the…

High Energy Physics - Theory · Physics 2008-11-26 L. Ravagli , J. J. M. Verbaarschot

We study quenched QCD just above the phase transition temperature using overlap Fermions. Exact zero modes of the overlap operator are localized. Chiral symmetry is restored, as indicated by the behavior of the chiral condensate after…

High Energy Physics - Lattice · Physics 2015-06-25 R. V. Gavai , Sourendu Gupta , R. Lacaze

In Quantum Chromodynamics (QCD) the eigenmodes of the Dirac operator with small absolute eigenvalues have a close relationship to the dynamical breaking of the chiral symmetry. In a simulation with two dynamical quarks, we study the…

High Energy Physics - Lattice · Physics 2015-03-19 C. B. Lang , Mario Schröck

Temporal quark correlation functions are analyzed in quenched lattice QCD for two values of temperature above the critical temperature (Tc) for deconfinement, T=1.5Tc and 3Tc. A two-pole ansatz for the quark spectral function is used to…

High Energy Physics - Lattice · Physics 2013-05-30 Olaf Kaczmarek , Frithjof Karsch , Masakiyo Kitazawa , Wolfgang Soeldner

Aoki, Fukaya, and Taniguchi claim that both the spectral density of the Dirac operator at the origin and the topological susceptibility must vanish identically for sufficiently small but nonzero mass $m$ in the chirally symmetric phase of…

High Energy Physics - Lattice · Physics 2025-10-29 Matteo Giordano

We propose a framework for quantitative evaluation of dynamical tendency for polarization in arbitrary random variable that can be decomposed into a pair of orthogonal subspaces. The method uses measures based on comparisons of given…

High Energy Physics - Lattice · Physics 2011-08-05 Andrei Alexandru , Terrence Draper , Ivan Horvath , Thomas Streuer