Giovanni Forni

Abstract:   It is known that the equidistribution of the fractional parts of polynomials sequences with irrational leading coeeficient can be derived from the unique ergodicity of nilpotent maps on the torus or, equivalently, of homogeneous flows on nilmanifolds. We will present some results on the speed of convergence of ergodic averages of nilflows under Diophantine conditions and discuss the relation with known results and conjectures on Weyl sums (exponential sums for polynomial sequences). Our approach is based on methods from the theory of dynamical systems (cohomological equations, invariant distributions, renormalization). The content of this talk is joint work with L. Flaminio (Lille).

Here are some directions to Northeastern University. Lake Hall and Nightingale Hall can be best accessed from the entrance on the corner of Greenleaf Street and Leon Street. The two halls are connected, with no well-defined boundary in between. In particular, 509 Lake Hall is on the same corridor as 544 Nightingale Hall.

There is free parking available for people coming to the Colloquium at Northeastern's visitor parking (Rennaisance Garage). The entrance is from Columbus Avenue. If coming by car, you should park there and take the parking talon. After the lecture, you may pick up the payment coupon from Andrei Zelevinsky.