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Two twisted doublets, one containing the up and down quarks and the other containing the strange quark with an isospin partner, are used for studies in the meson sector. The relevant chiral perturbation theory is presented, and quenched QCD simulations (where the partner of the strange quark is not active) are performed. Pseudoscalar meson masses and decay… (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)

Hadron masses are computed from quenched twisted mass lattice QCD for a degenerate doublet of up and down quarks with the twist angle set to π/2, since this maximally twisted theory is expected to be free of linear discretization errors. Two separate definitions of the twist angle are used, and the hadron masses for these two cases are compared. The flavor… (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. Eigenvectors are generated during solution of the first right-hand side and used… (More)

- Abdou M. Abdel-Rehim, Andreas T 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 reorthogonalization is used in order to control roundoff errors associated with the… (More)

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)

A deflated and restarted Lanczos algorithm to solve hermitian linear systems, and at the same time compute eigenvalues and eigenvectors for application to multiple right-hand sides, is described. For the first right-hand side, eigenvectors with small eigenvalues are computed while simultaneously solving the linear system. Two versions of this algorithm are… (More)

- Fermion Operators, Abdou M. 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)