Slow Relaxation in a Model with Many Conservation Laws : Deposition and Evaporation of Trimers on a Line

We study the slow decay of the steady-state autocorrelation function $C(t)$ in a stochastic model of deposition and evaporation of trimers on a line with infinitely many conservation laws and sectors. Simulations show that $C(t)$ decays as different powers of $t$, or as $\exp (-t^{1/2})$, depending on the sector. We explain this diversity by relating the problem to diffusion of hard core particles with conserved spin labels. The model embodies a matrix generalization of the Kardar-Parisi-Zhang model of interface roughening. In the sector which includes the empty line, the dynamical exponent $z$ is $2.55 \pm 0.15$.