Critical slowing down Monte Carlo algorithms

Inserting complete sets of basis states between the different Hi factors then leads to a similar representation of the partition function and a similar world-line picture as in the world-line Monte Carlo method. Because there is no Trotter decomposition involved, the method is free of time discretization errors from the outset. Early applications of the SSE method employed local updates, but more efficient cluster-type updates have been developed more recently to overcome the critical slowing down. They include the operator-loop update and the previously mentioned directed-loop algorithm. ... 

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