[Triumf-seminars] TRIUMF Theory Seminar today at 13:00

[TRIUMF Seminars]

Date/Time: Tue 2011-11-01 at 13:00

Location:  Theory Room         

Speaker:   Saul Cohen (U Washington/INT)

Title:     Multigrid Algorithms for Accelerating Fermion Calculations in Lattice QCD

Abstract: Lattice gauge theory has successfully described many aspects of the
strong interaction from the first principles of QCD. However,
calculations of nuclear physics or ``disconnected'' diagrams require
much more computational power to achieve the precision needed to have
phenomenological impact. Thus, we rely not only on the increase in
available computational resources but also on smart algorithms that
make the most of currently available hardware.

In this talk, I describe adaptive multigrid algorithms for solving
inverses of the Dirac fermion operator, particularly the difficult
case of chiral domain-wall fermions. Our multigrid algorithm uses an
adaptive projection of near-null vectors of the Dirac operator onto
coarser four-dimensional lattices. This extension of multigrid
techniques to a chiral fermion action will greatly reduce overall
computation cost, and the elimination of the fifth dimension in the
coarse space reduces the relative cost of using chiral fermions
compared to discarding this symmetry. We demonstrate near-elimination
of critical slowing as the quark mass is reduced and small volume
dependence, which may be suppressed by taking advantage of the
recursive nature of the algorithm.



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