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The application of Random Matrix Theory to the Dirac operator of QCD yields predictions for the probability distributions of the lowest eigenvalues. We measured Dirac operator spectra using massless overlap fermions in quenched QCD at…

High Energy Physics - Lattice · Physics 2009-11-10 S. Shcheredin , W. Bietenholz , T. Chiarappa , K. Jansen , K. -I. Nagai

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 the epsilon-regime of QCD the main features of the spectrum of the low-lying eigenvalues of the (euclidean) Dirac operator are expected to be described by a certain universality class of random matrix models. In particular, the latter…

High Energy Physics - Lattice · Physics 2009-11-10 Leonardo Giusti , Martin Lüscher , Peter Weisz , Hartmut Wittig

We calculate numerically the eigenvalue distribution of the overlap Dirac operator in the quenched Schwinger model on a lattice. The distribution does not fit any of the three universality classes of spontaneous chiral symmetry breaking,…

High Energy Physics - Lattice · Physics 2009-11-11 Poul H. Damgaard , Urs M. Heller , Rajamani Narayanan , Benjamin Svetitsky

We analyze how individual eigenvalues of the QCD Dirac operator at nonzero quark chemical potential are distributed in the complex plane. Exact and approximate analytical results for both quenched and unquenched distributions are derived…

High Energy Physics - Lattice · Physics 2008-11-26 G. Akemann , J. Bloch , L. Shifrin , T. Wettig

We investigate a number of algorithms that calculate the quark propagators for the overlap-Dirac fermion operator. The QCD simulations were performed at beta = 5.9 with a lattice volume of 16**3*32.

High Energy Physics - Lattice · Physics 2015-06-25 UKQCD Collaboration , Craig McNeile , Alan Irving , Chris Michael

We calculate the chiral condensate of QCD with 2, 2+1 and 3 flavors of sea quarks. Lattice QCD simulations are performed employing dynamical overlap fermions with up and down quark masses covering a range between 3 and 100 MeV. On L ~…

High Energy Physics - Lattice · Physics 2015-03-17 H. Fukaya , S. Aoki , T. W. Chiu , S. Hashimoto , T. Kaneko , J. Noaki , T. Onogi , N. Yamada

I propose a simple model of the distribution of the small eigenvalues of the QCD Dirac operator well above the finite temperature phase transition where chiral symmetry is restored and the spectral density at zero vanishes. Assuming the…

High Energy Physics - Lattice · Physics 2010-11-11 Tamas G. Kovacs

The properties of the spectrum of the overlap Dirac operator and their relation to random matrix theory are studied. In particular, the predictions from chiral random matrix theory in topologically non-trivial gauge field sectors are…

High Energy Physics - Lattice · Physics 2015-06-25 Robert G. Edwards , Urs M. Heller , Joe Kiskis , Rajamani Narayanan

We compute fermionic observables relevant to the study of chiral symmetry in quenched QCD using the Overlap-Dirac operator for a wide range of the fermion mass. We use analytical results to disentangle the contribution from exact zero modes…

High Energy Physics - Lattice · Physics 2009-10-31 Robert G. Edwards , Urs M. Heller , Rajamani Narayanan

The low energy eigenmodes of the continuum QCD Dirac operator are extended, but on the lattice, due to discretization effects, the Dirac operator can have localized eigenmodes. These non-physical modes can introduce strong lattice artifacts…

High Energy Physics - Lattice · Physics 2009-04-14 Anna Hasenfratz , Roland Hoffmann , Stefan Schaefer

In this lecture we review recent lattice QCD studies of the statistical properties of the eigenvalues of the QCD Dirac operator. We find that the fluctuations of the smallest Dirac eigenvalues are described by chiral Random Matrix Theories…

High Energy Physics - Lattice · Physics 2009-10-31 J. J. M. Verbaarschot

The spectrum of the overlap Dirac operator in the deconfined phase of quenched gauge theory is known to have three parts: exact zeros arising from topology, small nonzero eigenvalues that result in a non-zero chiral condensate, and the…

High Energy Physics - Lattice · Physics 2009-11-07 Joe Kiskis , Rajamani Narayanan

We consider antisymmetric perturbations of real symmetric matrices in the context of random matrix theory and two-color quantum chromodynamics. We investigate the level spacing distributions of eigenvalues that remain real or become complex…

High Energy Physics - Lattice · Physics 2012-08-30 Jacques Bloch , Falk Bruckmann , Nils Meyer , Sebastian Schierenberg

We report on the two-flavor QCD simulation in the epsilon-regime using the overlap fermion formulation. Sea quark mass is reduced to ~ 2 MeV on a 16^3x32 lattice with the lattice spacing ~ 0.11fm. Topological charge is fixed at Q=0. We…

High Energy Physics - Lattice · Physics 2008-11-26 JLQCD collaboration , H. Fukaya , S. Hashimoto , K. Kanaya , T. Kaneko , H. Matsufuru , K. Ogawa , M. Okamoto , T. Onogi , N. Yamada

For QCD at non-zero chemical potential $\mu$, the Dirac eigenvalues are scattered in the complex plane. We define a notion of ordering for individual eigenvalues in this case and derive the distributions of individual eigenvalues from…

High Energy Physics - Lattice · Physics 2009-01-14 Gernot Akemann , Jacques Bloch , Leonid Shifrin , Tilo Wettig

We compute the low-lying spectrum of the staggered Dirac operator above and below the finite temperature phase transition in both quenched QCD and in dynamical four flavor QCD. In both cases we find, in the high temperature phase, a density…

High Energy Physics - Lattice · Physics 2009-10-31 P. H. Damgaard , U. M. Heller , R. Niclasen , K. Rummukainen

We investigate the spectral properties of the Wilson Dirac operator in quenched QCD in the microscopic regime. We distinguish the topological sectors using the index as determined by the Wilson flow method. Consequently, the distributions…

High Energy Physics - Lattice · Physics 2012-01-04 Albert Deuzeman , Urs Wenger , Jair Wuilloud

We measure the low lying eigenmodes of an overlap Dirac operator on 2--flavor staggered configurations. By comparing the eigenmode distribution to the predictions of Random Matrix Theory we test to what accuracy staggered configurations…

High Energy Physics - Lattice · Physics 2008-11-26 Anna Hasenfratz , Roland Hoffmann

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

High Energy Physics - Phenomenology · Physics 2007-05-23 Elmar Bittner , Maria-Paola Lombardo , Harald Markum , Rainer Pullirsch
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