Shape diffusion in the shell model

The diffusion coefficient for quadrupolar shape changes is derived in a model based on the mixing of static Hartree-Fock configurations by the residual interaction. The model correctly predicts the width of single-particle configurations. We find a diffusion rate depending on temperature as ${\mathit{T}}^3$, consistent with at least one other theoretical estimate. However, our diffusion rate is an order of magnitude lower than two values extracted from data.