On the Sign Problem in the Hirsch-Fye Algorithm for Impurity Problems

Yoo, Jaebeom; Chandrasekharan, Shailesh; Kaul, Ribhu K.; Ullmo, Denis; Baranger, Harold U.

On the Sign Problem in the Hirsch-Fye Algorithm for Impurity Problems

Authors

Yoo, Jaebeom

Chandrasekharan, Shailesh

Kaul, Ribhu K.

Ullmo, Denis

Baranger, Harold U.

Description

We show that there is no fermion sign problem in the Hirsch and Fye algorithm for the single-impurity Anderson model. Beyond the particle-hole symmetric case for which a simple proof exists, this has been known only empirically. Here we prove the nonexistence of a sign problem for the general case by showing that each spin trace for a given Ising configuration is separately positive. We further use this insight to analyze under what conditions orbitally degenerate Anderson models or the two-impurity Anderson model develop a sign.
2 pages, no figure; published version