9905089.pdf (64.93 kB)
Exact classical effective potentials
preprint
posted on 2006-04-12, 10:08 authored by John SamsonA quantum spin system can be modelled by an equivalent classical system, with an effective Hamiltonian obtained by integrating all non-zero frequency modes out of the path integral. The effective Hamiltonian H_eff(S_i) derived from the coherent-state integral is highly singular: the quasiprobability density exp(-beta H_eff), a Wigner function, imposes quantisation through derivatives of delta functions. This quasiprobability is the distribution of the time-averaged lower symbol of the spin in the coherent-state integral. We relate the quantum Monte Carlo minus-sign problem to the non-positivity of this quasiprobability, both analytically and by Monte Carlo integration.
History
School
- Science
Department
- Physics
Pages
66492 bytesPublication date
1999Notes
This is a pre-print. It is also available at: http://arxiv.org/abs/quant-ph/9905089.Language
- en