Periodic perturbations with rotational symmetry of planar systems driven by a central force

Por Alessandro Fonda (Università degli Studi di Udine).

Abstract: We consider periodic perturbations of a central force field having a rotational symmetry, and prove the existence of nearly circular periodic orbits. We thus generalize, in the planar case, some previous bifurcation results obtained by Ambrosetti and Coti Zelati. Our results apply, in particular, to the classical Kepler problem.

On the Cauchy problem for the wave equation on time-dependent domains

Por Rodica Toader (Università degli Studi di Udine).

Abstract: The mathematical formulation of problems in dynamic fracture mechanics leads naturally to the study of the wave equation on domains which vary in time. We provide a notion of solution to the wave equation on a suitable class of time-dependent domains and show existence and uniqueness for the solutions of the Cauchy problem.

The results are obtained in collaboration with G. Dal Maso (SISSA, Trieste).

Nonlinear Dirichlet Problems: Old and New

Por Lucio Boccardo (Dipartimento di Matematica, "Sapienza" Università di Roma).

Abstract: We present a review on the Stampacchia-Calderon-Zygmund theory for linear elliptic operators of second order with discontinuous coefficients and the corresponding theory for nonlinear operators of Leray-Lions type with nonregular data.

We shall also discuss classical and recent results, including work in progress, on the continuous dependence of the solutions with respect to right hand sides.