Laurent Baratchart

Title: Some topological aspects of rational approximation

Abstract: starting from uniqueness properties for monosplines
in real approximation based on degree theory, we describe results
in complex approximation ( e.g. n-width estimates, lower bounds
and uniqueness issues rational and meromorphic approximation),
where critical point theory is a decisive tool. The geometry of finite
Blaschke products plays an important role in all of them. We also
discuss some open problems and matrix valued analogs.