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Results on the hadron masses for a degenerate doublet of up and down quarks from quenched twisted mass lattice QCD at maximal twist are presented. Two definitions of maximal twist are used and the hadron masses for these definitions are compared. Mass splittings within the ∆(1232) multiplet due to flavor breaking effects are discussed. c Copyright owned by… (More)

- Abdou M. Abdel-Rehim, Ronald B. Morgan, Dywayne A. Nicely, Walter Wilcox
- SIAM J. Scientific Computing
- 2010

A deflated restarted Lanczos algorithm is given for both solving symmetric linear equations and computing eigenvalues and eigenvectors. The restarting limits the storage so that finding eigenvectors is practical. Meanwhile, the deflating from the presence of the eigenvectors allows the linear equations to generally have good convergence in spite of the… (More)

The large systems of complex linear equations that are generated in QCD problems often have multiple right-hand sides (for multiple sources) and multiple shifts (for multiple masses). Deflated GMRES methods have previously been developed for solving multiple right-hand sides. Eigen-vectors are generated during solution of the first right-hand side and used… (More)

- Abdou M. Abdel-Rehim, Andreas Stathopoulos, Konstantinos Orginos
- Numerical Lin. Alg. with Applic.
- 2014

The technique that was used to build the eigCG algorithm for sparse symmetric linear systems is extended to the nonsymmetric case using the BiCG algorithm. We show that, similarly to the symmetric case, we can build an algorithm that is capable of computing a few smallest magnitude eigenvalues and their corresponding left and right eigenvectors of a… (More)

- Abdou M. Abdel-Rehim, Ronald B. Morgan, Walter Wilcox
- Numerical Lin. Alg. with Applic.
- 2014

We consider symmetric positive definite systems of linear equations with multiple right-hand sides. The seed conjugate gradient method solves one right-hand side with the conjugate gradient method and simultaneously projects over the Krylov subspace thus developed for the other right-hand sides. Then the next system is solved and used to seed the remaining… (More)

We consider three improvements to seed methods for Hermitian linear systems with multiple right-hand sides: only the Krylov subspace for the first system is used for seeding subsequent right-hand sides, the first right-hand side is solved past convergence, and periodic re-orthogonalization is used in order to control roundoff errors associated with the… (More)

1Goethe-Universität Frankfurt am Main, Institut für theoretische Physik, Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany 2Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Kavafi Street, 2121 Nicosia, Cyprus 3Department of Physics, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus 4NIC, DESY, Platanenallee… (More)

- Fermion Operators, Abdou Abdel-Rehim, Randy Lewis, Walter Wilcox
- 2007

Using noise methods on a quenched 20 3 × 32 lattice at β = 6.0, we have investigated vacuum expectation values and relative linear correlations among the various Wilson and twisted mass scalar and pseudoscalar disconnected loop operators. We show results near the maximal twist lines in κ, µ parameter space, either defined as the absence of parity mixing or… (More)

- Marc Wagner, Abdou Abdel-Rehim, +5 authors Carsten Urbach
- 2013

We review the status of an ongoing long-term lattice investigation of the spectrum and structure of tetraquark candidates. We focus on the light scalar meson a0(980). First steps regarding the study of a possibly existing ccc̄c̄ tetraquark are also outlined.

We discuss and compare the efficiency of various methods, combinations of point-to-all propagators, stochastic timeslice-to-all propagators, the one-end trick and sequential propagators, to compute two-point correlation functions of two-quark and four-quark interpolating operators of different structure including quark-antiquark type, mesonic molecule type,… (More)