QUANTUM MONTE-CARLO ALGORITHMS USING COHERENT STATES

We consider several algorithms for discrete approximations for path in tegrals to be used in the study of the thermodynamics of boson and spi n systems. We use coherent states as an expansion basis for both boson s and spins (Bloch coherent states) and compare algorithms using matri x elements or diagonal representatives or both. Since the overlaps bet ween the coherent states are in general complex, the use of the algori thms in the quantum Monte Carlo study carries the so-called sign probl em. In the case of a simple harmonic oscillator we find that some algo rithms in phase space give better accuracy than the traditional algori thm in configuration space. In the case of a spin in a magnetic field we find that the algorithms using the diagonal representative yield be tter results than those with matrix elements.