  The properties of dynamic (least action) fission paths are analyzed and
compared to the ones of the more traditional static (least energy) paths. Both
the BCPM and Gogny D1M energy density functionals are used in the calculation
of the HFB constrained configurations providing the potential energy and
collective inertias. The action is computed as in the WKB method. A full
variational search of the least-action path over the complete variational space
of HFB wave functions is cumbersome and probably unnecessary if the relevant
degrees of freedom are identified. In this paper, we consider the particle
number fluctuation degree of freedom that explores the amount of pairing
correlations in the wave function. For a given shape, the minimum action can be
up a factor of three smaller than the action computed for the minimum energy
state with the same shape. The impact of this reduction on the lifetimes is
enormous and dramatically improves the agreement with experimental data in the
few examples considered.
