Algorithms for Disconnected Diagrams in Lattice QCD
  Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm. 
Arjun Singh Gambhir, Andreas Stathopoulos, Kostas Orginos, Boram Yoon,   Rajan Gupta, Sergey Syritsyn
hep-lat