Evolving width Gaussian wave packets

To deal with the problem of using a superposition of functions, Heller also tried using Gaussian wave packets with a fixed width as a time-dependent basis set for the representation of the evolving nuclear wave function [23]. Each frozen Gaussian function evolves under classical equations of motion, and the phase is provided by the classical action along the path... 

Gaussian wave packet with evolving width... 

A more general coherent state description of a Gaussian wave packet is required when we allow the width parameter to evolve in time. The corresponding Lie group is then Sp(2, K), which is isomorphic to SU(1,1) or SO(2,1). The generators of the Sp(2, R) Lie algebra are... 

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