Properties of critical points and operators in economics

The study of the local characteristics of equilibrium positions generated by the constrained maximization of some criterion functions (such as utility, profit, cost, etc.) goes back to Antonelli's paper [2] of 1886. Certain local properties have been proved to be particularly fruitful for economic theory since the early works of Slutsky, Hicks, and Samuelson [9]; they have been formulated in terms of a matrix of "compensated" terms and they concern the properties of partial derivatives of the demand function in some neighborhood of the equilibrium. We now discuss this matrix and its applications.