Glassy dynamics and aging in an exactly solvable spin model

We introduce a simple two-dimensional spin model with short-range interacti ons which shows glassy behavior despite a Hamiltonian which is completely h omogeneous and possesses no randomness. We solve exactly for both the stati c partition function of the model and the distribution of energy barriers, giving us the equilibration time scales at low temperature. Simulations of instantaneous quenches and of annealing of the model are in good agreement with the analytic calculations. We also measure the two-time spin correlati on as a function of waiting time, and show that the model has aging behavio r consistent with the distribution of barrier heights. The model appears to have no sharp glass transition. Instead, it falls out of equilibrium at a temperature which decreases logarithmically as a function of the cooling ti me. [S1063-651X(99)04311-1].