  Despite recent advances and focus on rigorous uncertainty quantification for
microscopic models of quantum many-body systems, the uncertainty on the
dynamics of those systems has been under-explored. To address this, we have
used time-dependent Hartree-Fock to examine the model uncertainty for a
collection of low-energy, heavy-ion fusion reactions. Fusion reactions at
near-barrier energies represent a rich test-bed for the dynamics of quantum
many-body systems owing to the complex interplay of collective excitation,
transfer, and static effects that determine the fusion probability of a given
system. While the model uncertainty is sizable for many of the systems studied,
the primary contribution comes from ill-constrained static properties, such as
the neutron radius of neutron-rich nuclei. These large uncertainties motivate
the use of information from reactions to better constrain existing models and
to infer static properties from reaction data.
