Unified contraction algorithm for multi-baryon correlators on the lattice. (arXiv:1205.0585v1 [hep-lat])

We propose a novel algorithm for calculating multi-baryon correlation
functions on the lattice. By considering the permutation of quarks (Wick
contractions) and color/spinor contractions simultaneously, we construct a
unified index list for the contraction where the redundancies in the original
contraction are eliminated. We find that a significant reduction in the
computational cost of correlators is achieved, e.g., by a factor of 192 for
$ ^3$ H and $ ^3$ He nuclei, and a factor of 20736 for the $ ^4$ He nucleus, without
assuming isospin symmetry. A further reduction is possible by exploiting
isospin symmetry, and/or interchange symmetries associated with sink baryons,
if such symmetries exist. Extensions for systems with hyperons are presented as
well.

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