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We study quenched QCD at finite chemical potential, $\mu_I$, for the third component of isospin and quenched two-colour QCD at finite chemical potential, $\mu$, for quark number. In contrast to the quenched approximation to QCD at finite…

High Energy Physics - Lattice · Physics 2009-11-07 J. B. Kogut , D. K. Sinclair

I report on first results of the ETMC obtained simulating lattice QCD with two degenerate flavours of Wilson twisted mass fermions, for which physical observables are automatically O(a) improved. Recent improvements of the HMC algorithm…

High Energy Physics - Phenomenology · Physics 2007-05-23 Andrea Shindler , ETM Collaboration

We present a formula for reducing the rank of Wilson fermions from $4 N_c N_x N_y N_z N_t$ to $4 N_c N_x N_y N_z$ keeping the value of its determinant. We analyse eigenvalues of a reduced matrix and coefficients $C_n$ in the fugacity…

High Energy Physics - Lattice · Physics 2010-12-23 Keitaro Nagata , Atsushi Nakamura

We simulate quenched QCD with the overlap Dirac operator. We work with the Wilson gauge action at beta=6 on an 18^3x64 lattice. We calculate quark propagators for a single source point and quark mass ranging from am_q=0.03 to 0.75. We…

High Energy Physics - Lattice · Physics 2009-11-10 Federico Berruto , Nicolas Garron , Christian Hoelbling , Laurent Lellouch , Claudio Rebbi , Noam Shoresh

We present preliminary lattice results for the nonperturbative tensor structure of the vector and axial-vector quark-antiquark vertices in QCD. Our lattice calculations are for $N_f=2$ mass-degenerate Wilson fermion flavors whose quark mass…

High Energy Physics - Lattice · Physics 2019-04-25 André Sternbeck , Milena Leutnant , Gernot Eichmann

In the large fermion mass limit of QCD at finite density the structure of the partition function greatly simplifies and can be studied analytically. We show that, contrary to general wisdom, the phase of the Dirac determinant is relevant…

High Energy Physics - Lattice · Physics 2009-10-31 R. Aloisio , V. Azcoiti , G. Di Carlo , A. Galante , A. F. Grillo

We calculate the large-volume and small-mass dependences of the quark condensate in quenched QCD using Neuberger's operator. We find good agreement with the predictions of quenched chiral perturbation theory, enabling a determination of the…

High Energy Physics - Lattice · Physics 2015-06-25 Pilar Hernandez , Karl Jansen , Laurent Lellouch

It is possible to numerically solve QCD in the planar limit using standard numerical techniques on existing computer clusters. The basic ideas behind the computational strategy an recent numerical results in the fermionic sector of large N…

High Energy Physics - Lattice · Physics 2017-08-23 R. Narayanan , H. Neuberger

We give a general introduction and discussion of the issues involved in using the twisted mass formulation of lattice fermions in the context of disconnected loop calculations, including a short orientation on the present experimental…

High Energy Physics - Lattice · Physics 2007-05-23 Walter Wilcox , Dean Darnell , Ron Morgan , Randy Lewis

We show that all current formalisms for quarks in lattice QCD are consistent in the quenched continuum limit, as they should be. We improve on previous extrapolations to this limit, and the understanding of lattice systematic errors there,…

High Energy Physics - Lattice · Physics 2009-11-10 C. T. H. Davies , G. P. Lepage , F. Niedermayer , D. Toussaint

We present a reduction method for Wilson Dirac fermions with non-zero chemical potential which generates a dimensionally reduced fermion matrix. The size of the reduced fermion matrix is independent of the temporal lattice extent and the…

High Energy Physics - Lattice · Physics 2011-02-18 Andrei Alexandru , Urs Wenger

The results of a high-statistics study of scalar and pseudoscalar meson propagators in quenched lattice QCD are presented. For two values of lattice spacing, $\beta=5.7$ ($a \approx .18$ fm) and 5.9 ($a \approx .12$ fm), we probe the light…

High Energy Physics - Lattice · Physics 2009-11-10 W. Bardeen , E. Eichten , H. Thacker

We determine the chiral condensate from simulations of quenched lattice QCD with Wilson fermions. Our measurements have been obtained with high statistics at three values of the gauge coupling, corresponding to UV cutoffs in the range 2 - 4…

High Energy Physics - Lattice · Physics 2009-10-31 L. Giusti , F. Rapuano , M. Talevi , A. Vladikas

We study the impact of explicit chiral symmetry breaking of Wilson fermions on mesonic correlators in the epsilon-regime using Wilson chiral perturbation theory (WChPT). We generalize the epsilon-expansion of continuum ChPT to nonzero…

High Energy Physics - Lattice · Physics 2009-03-27 Oliver Bar , Silvia Necco , Stefan Schaefer

The chiral extension of Quantum Chromodynamics (XQCD) adds to the standard lattice action explicit pseudoscalar meson fields for the chiral condensates. With this action, it is feasible to do simulations at the chiral limit with zero mass…

High Energy Physics - Lattice · Physics 2009-10-28 R. C. Brower , K. Orginos , C-I Tan

We compute the hadron mass spectrum, the quark masses and the meson decay constants in quenched lattice QCD with non-perturbatively $O(a)$ improved Wilson fermions. The calculations are done for two values of the coupling constant, $\beta =…

High Energy Physics - Lattice · Physics 2008-11-26 M. Göckeler , R. Horsley , H. Perlt , P. Rakow , G. Schierholz , A. Schiller , P. Stephenson

We simulate lattice QCD at finite quark-number chemical potential, $\mu$, using the complex-Langevin equation (CLE) with gauge-cooling and adaptive updating to prevent instabilities. The CLE is used because QCD at finite $\mu$ has a complex…

High Energy Physics - Lattice · Physics 2018-10-30 D. K. Sinclair , J. B. Kogut

We develop a strategy for the non-perturbative determination of the O(a)-improvement coefficient c_sw for Wilson fermions with massive sea quarks. The improvement condition is defined via the PCAC relation in the Schr\"odinger functional.…

High Energy Physics - Lattice · Physics 2015-01-28 Patrick Fritzsch , Rainer Sommer , Felix Stollenwerk , Ulli Wolff

The order of the thermal transition in the chiral limit of QCD with two dynamical flavours of quarks is a long-standing issue. Still, it is not definitely known whether the transition is of first or second order in the continuum limit.…

High Energy Physics - Lattice · Physics 2015-09-01 Owe Philipsen , Christopher Pinke

The maximally twisted lattice QCD action of an $SU_f(2)$ doublet of mass degenerate Wilson quarks gives rise to a real positive fermion determinant and it is invariant under the product of standard parity times the change of sign of the…

High Energy Physics - Lattice · Physics 2009-11-10 R. Frezzotti , G. C. Rossi