### Existence and uniqueness for dynamical unilateral contact with Coulomb friction : a model problem

A simple dynamical problem involving unilateral contact and dry friction of Coulomb type is considered as an archetype. We are concerned with the existence and uniqueness of solutions of the system with Cauchy data. In the frictionless case, it is known [Schatzman, Nonlinear Anal. Theory, Methods Appl. 2 (1978) 355–373] that pathologies of non-uniqueness can exist, even if all the data are of class ${C}^{\infty}$. However, uniqueness is recovered provided that the data are analytic [Ballard, Arch. Rational Mech....