Maximum Entropy Method Approach to θ Term

In Monte Carlo simulations of lattice field theory with a θ term, one confronts the complex weight problem, or the sign problem. This is circumvented by performing the Fourier transform of the topological charge distribution P (Q). This procedure, however, still causes the flattening phenomenon of the free energy, which prevents one from studying the phase structure. In order to work at this issue, we apply the maximum entropy method (MEM) to the Gaussian P (Q), which serves as a good laboratory to test whether the MEM works for the θ term. We study the case with the flattening as well as the one without the flattening. For the latter case, the results of the MEM agree with the Fourier transform, and for the former the flattening is much improved. ∗) E-mail: [email protected] ∗∗) E-mail: [email protected] ∗∗∗) E-mail: [email protected] 1 typeset using PTPTEX.cls 〈Ver.0.88〉 §