  We consider the quench dynamics of a two-dimensional quantum dimer model and
determine the role of its kinematic constraints. We interpret the
non-equilibrium dynamics in terms of the underlying equilibrium phase
transitions consisting of a BKT-transition between a columnar ordered valence
bond solid (VBS) and a valence bond liquid (VBL), as well as a first order
transition between a staggered VBS and the VBL. We find that quenches from a
columnar VBS are ergodic and both order parameters and spatial correlations
quickly relax to their thermal equilibrium. By contrast, the staggered side of
the first order transition does not display thermalization on numerically
accessible timescales. Based on the model's kinematic constraints, we uncover a
mechanism of relaxation that rests on emergent, highly detuned multi-defect
processes in a staggered background, which gives rise to slow, glassy dynamics
at low temperatures even in the thermodynamic limit.
