We present a general framework for understanding the transition from local regular to global irregular (chaotic) behavior of nonlinear dynamical models in discrete time. The fundamental mechanism is the unfolding of quadratic tangencies between the stable and the unstable manifolds of periodic...

We develop in this paper simple geometrical methods to study local indeterminacy, bifurcations and stochastic (sunspot) equilibria near a steady state, in nonlinear two dimensional economic models. We present in particular a simple geometrical characterization of the support of stochastic...