Computational method for multidimensional quantal dynamics of polynomially interacting oscillator systems.

: We propose a numerical algorithm for computing quantal dynamics, which is tailored for a generic multidimensional model of low-energy dynamics, i.e., polynomially interacting oscillator system. This algorithm evaluates symplectic integrators effectively, by using block tridiagonality of the interaction operator, and thus accurately preserves unitarity with time. A practical advantage of this method is that high-order integrators are easily implemented even for time-dependent parameter systems. We demonstrate the accuracy and usefulness by applying it to a phi(4) model.