  The probability of accepting a candidate move in the hybrid Monte Carlo
algorithm can be increased by considering a transition to be between windows of
several states at the beginning and end of the trajectory, with a state within
the selected window being chosen according to the Boltzmann probabilities. The
detailed balance condition used to justify the algorithm still holds with this
procedure, provided the start state is randomly positioned within its window.
The new procedure is shown empirically to significantly improve performance for
a test system of uncoupled oscillators.
