# Annette Huber-Klawitter

### Periods and Nori motives

**Abstract:** (joint work with Stefan MÃ¼ller-Stach)

Periods are numbers that one gets by integrating a rational differential form over a cycle. They form a very interesting subalgebra of the complex number, including e.g. \pi, \log(2), \zeta(n) for all n\in \Z The period

conjecture says that the only relation between these periods are the obvious ones. This is a very strong assertion on transcendence. In the talk I am going to make this statement precise by introducing Kontsevich's algebra of formal periods. Following ideas of Kontsevich and Nori, we then show that the corresponding proalgebraic scheme is a torsor under the motivic Galois group in the sense of Nori.