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In quantum chromodynamics (QCD) at nonzero chemical potential, the eigenvalues of the Dirac operator are scattered in the complex plane. Can the fluctuation properties of the Dirac spectrum be described by universal predictions of…

High Energy Physics - Lattice · Physics 2009-10-31 H. Markum , R. Pullirsch , T. Wettig

We consider the effect of discretization errors on the microscopic spectrum of the Wilson Dirac operator using both chiral Perturbation Theory and chiral Random Matrix Theory. A graded chiral Lagrangian is used to evaluate the microscopic…

High Energy Physics - Lattice · Physics 2015-03-17 G. Akemann , P. H. Damgaard , K. Splittorff , J. J. M. Verbaarschot

We show how to introduce a quark chemical potential in the overlap Dirac operator. The resulting operator satisfies a Ginsparg-Wilson relation and has exact zero modes. It is no longer gamma_5-hermitian, but its nonreal eigenvalues still…

High Energy Physics - Lattice · Physics 2009-01-14 Jacques Bloch , Tilo Wettig

We study physics at temperatures just above the QCD phase transition (Tc) using chiral (overlap) Fermions in the quenched approximation of lattice QCD. Exact zero modes of the overlap Dirac operator are localized and their frequency of…

High Energy Physics - Lattice · Physics 2011-07-19 Rajiv V. Gavai , Sourendu Gupta , R. Lacaze

We explore the properties of low lying eigenmodes of fermions in the quenched approximation of lattice QCD. The fermion action is a recently proposed overlap action and has exact chiral symmetry. We find that chiral zero-eigenvalue modes…

High Energy Physics - Lattice · Physics 2009-10-31 Thomas DeGrand , Anna Hasenfratz

We analyze the localization properties for eigenvectors of the Dirac operator in quenched lattice QCD in the vicinity of the deconfinement phase transition. Studying the characteristic differences between the Z_3 sectors above the critical…

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

We discuss a possible mechanism leading to localisation of the low-lying Dirac eigenmodes in high-temperature lattice QCD, based on the spatial fluctuations of the local Polyakov lines in the partially ordered configurations above $T_c$.…

High Energy Physics - Lattice · Physics 2015-05-20 Matteo Giordano , Tamas G. Kovacs , Ferenc Pittler

We consider $4d$ compact lattice QED in the quenched approximation. First, we briefly summarize the spectrum of the staggered Dirac operator and its connection with random matrix theory. Afterwards we present results for the low-lying…

High Energy Physics - Lattice · Physics 2008-11-26 Bernd A. Berg , Urs M. Heller , Harald Markum , Rainer Pullirsch , Wolfgang Sakuler

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

Recently, random matrix theory predictions for the distribution of low-lying Dirac operator eigenvalues have been extended to include lattice effects for both staggered and Wilson fermions. We computed low-lying eigenvalues for the…

High Energy Physics - Lattice · Physics 2011-12-09 Urs M. Heller

We examine quenched chiral logarithms in lattice QCD with overlap Dirac quarks. From our data of m_pi^2, we determine the coefficient of quenched chiral logarithm delta = 0.203(14), 0.176(17), 0.193(17) and 0.200(13) for lattices of sizes…

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

In previous studies we have shown that hadrons, except for a pion, survive the removal of the lowest lying Dirac eigenmodes from the valence quark propagators. The low-modes are tied to the dynamical breaking of chiral symmetry and we found…

High Energy Physics - Lattice · Physics 2014-05-21 M. Schröck , M. Denissenya , L. Ya. Glozman , C. B. Lang

We reinvestigate constraints on the eigenvalue density of the Dirac operator in the chiral symmetric phase of 2 flavor QCD at finite temperature, employing the overlap Dirac operator with the exact chiral symmetry at finite lattice spacings…

High Energy Physics - Lattice · Physics 2012-12-10 Sinya Aoki , Hidenori Fukaya , Yusuke Taniguchi

We construct a lattice Dirac operator of overlap type that describes the propagation of a Dirac fermion in an external gravitational field. The local Lorentz symmetry is manifestly realized as a lattice gauge symmetry, while it is believed…

High Energy Physics - Lattice · Physics 2009-11-11 Masashi Hayakawa , Hiroto So , Hiroshi Suzuki

Because of the mass gap, lattice QCD simulations exhibit stochastic locality: distant regions of the lattice fluctuate independently. There is a long history of exploiting this to increase statistics by obtaining multiple…

High Energy Physics - Lattice · Physics 2023-12-01 Mattia Bruno , Marco Cè , Anthony Francis , Patrick Fritzsch , Jeremy R. Green , Maxwell T. Hansen , Antonio Rago

I define lattice fermions in five Euclidean dimensions and the corresponding effective theory in four dimensions. The main properties of these theories include the suppression of high momentum modes of the lattice Dirac operator and their…

High Energy Physics - Lattice · Physics 2008-11-26 Artan Borici

The QCD topological observables are essential inputs to obtain theoretical predictions about axion phenomenology, which are of utmost importance for current and future experimental searches for this particle. Among them, we focus on the…

We study the axial U(1)A symmetry of Nf = 2 QCD at finite temperature using the Dirac eigenvalue spectrum. The gauge configurations are generated employing the Mobius domain-wall fermion action on 16^3x8 and 32^3x8 lattices. The physical…

High Energy Physics - Lattice · Physics 2014-12-24 Akio Tomiya , Guido Cossu , Hidenori Fukaya , Shoji Hashimoto , Junichi Noaki

We study the eigenvalues of Dirac operators in QCD with two mass degenerate dynamical fermions. The gauge configurations have been obtained with HMC and the so-called Chirally Improved fermionic action. We compare eigenvalues obtained for…

High Energy Physics - Lattice · Physics 2009-04-14 Martina Joergler , C. B. Lang

An explicit, detailed evaluation of the classical continuum limit of the axial anomaly/index density of the overlap Dirac operator is carried out in the infinite volume setting, and in a certain finite volume setting where the continuum…

High Energy Physics - Lattice · Physics 2009-10-31 David H. Adams