The following four questions could be asked about each extremalproblem: 1. What are the conditions for an extremum of the problem (necessary, sufficient, necessary andsufficient)? 2. How to describe the evolution of sulutions if the problem is perturbed? 3. Does a solution to the problem exist...

We derive closed-form expressions for the Jacobian of the matrix exponential function for both diagonalizable and defective matrices. The results are applied to two cases of interest in macroeconometrics: a continuoustime macro model and the parametrization of rotation matrices governing impulse...

We characterise the entire set of symmetric stationary Markov-perfect Nash equilibria (MPE) in a differential game of public good investment, using the canonical problem of climate change as an example. We provide a sufficient and necessary condition for MPE and show how the entire set of MPE is...

In this paper we present two general results on the existence of a discrete zero point of a function from the n-dimensional integer lattice Zn to the n-dimensional Euclidean space Rn. Under two different boundary conditions, we give a constructive proof using a combinatorial argument based on a...