Energy degeneracies from microcanonical averages Original Research Article

A method for the direct calculation of the energy degeneracy g(E) has been recently introduced. One considers all possible potential modifications one can perform, starting from the current state of the system (for instance all possible spin flips), and counts the number Nup (Ndn) of such potential movements increasing (decreasing) the energy by a fixed value ΔE. The degeneracy g(E) can thus be determined from the microcanonical averages 〈Nup(E)〉 and 〈Ndn(E)〉 of these macroscopic quantities, measured as functions of the energy E. Any microcanonical simulator can be used in order to get these averages. Instead of simply measuring the histogram of the number of visits where each new state increases by unity the counter in the corresponding energy channel, here the counters are incremented by macroscopic quantities for each new visited state. Thus, we reach very good accuracy with little computational effort.