Glassiness and constrained dynamics of a short-range nondisordered spin model

We study the low temperature dynamics of a two-dimensional short-range spin system with uniform ferromagnetic interactions, which displays glassiness at low temperatures despite the absence of disorder or frustration. The mod el has a dual description in terms of free defects subject to dynamical con straints, and is an explicit realization of the "hierarchically constrained dynamics" scenario for glassy systems. We give a number of exact results f or the statics of the model, and study in detail the dynamical behavior of one-time and two-time quantities. We also consider the role played by the c onfigurational entropy, which can be computed exactly. in the relation betw een fluctuations and response.