A comparison between broad histogram and multicanonical methods

Abstract

We discuss the conceptual differences between the Broad Histogram (BHM) and reweighting methods in general, and particularly the so-called Multicanonical (MUCA) approaches. The main difference is that BHM is based on microcanonical, fixed-energy averages which depends only on the good statistics taken {\bf inside} each energy level. The detailed distribution of visits among different energy levels, determined by the particular dynamic rule one adopts, is irrelevant. Contrary to MUCA, where the results are extracted from the dynamic rule itself, within BHM any microcanonical dynamics could be adopted. As a numerical test, we have used both BHM and MUCA in order to obtain the spectral energy degeneracy of the Ising model in $4 \times 4 \times 4$ and $32 \times 32$ lattices, for which exact results are known. We discuss why BHM gives more accurate results than MUCA, even using {\bf the same} Markovian sequence of states. In addition, such advantage increases for larger systems.