Mardi 6 mai : seminaire annule.

Mardi 13 mai :  deux seminaires

14h15 : Yavdat Il'yasov (Universite de La Rochelle)

"On nonlocal calculation of bifurcations for the equations
of variational form. Application to inhomogeneous elliptic
boundary value problems."

Let $W$ be a Banach space and $I_{\lambda}$ a real functional of
class $C^1(W\setminus \{0\})$ which depends on the real parameter
$\lambda$. It is considered the problem of the existence of
critical points of $I_{\lambda}$ on $W$. To solve the problem,
firstly it has to be determined a suitable interval $(\lambda_j,
\lambda_{j+1}) \subseteq \Real$ in such a way that in the further
investigations it enables us to find the critical points of
$I_{\lambda}$ on $W$ for $\lambda \in (\lambda_j, \lambda_{j+1})$.
In general, the points $\lambda_j$ are bifurcation values for the
branch of the critical points of $I_{\lambda}$. In linear cases,
the calculation of these points $\lambda_j$ is a subject of the
spectral theory. However in nonlinear cases, it is absent such a
general theory; usually, the sufficient interval
$(\lambda_j,\lambda_{j+1}) \subseteq \Real$ are possibly guessed
by using a priori observations.
In the talk it will present a method for a constructive
calculation of the sufficient intervals for the given functional
$I_{\lambda}$ on Banach space with respect to the considered
parameter $\lambda$.
We illustrate the method on the example of a class of
inhomogeneous elliptic boundary value problems with indefinite
nonlinearities and on the class of the generalized
Ambrosetti-Brezis-Cerami problem with convex-concave
nonlinearities.

15h45 (avec le seminaire d'analyse de l'IGD) Piermarco Cannarsa (Universite de Rome 2) :

"Representation of equilibrium solutions to the table problem for growing
sandpiles"

20 et 27 mai : creneaux libres.