Date & Time: Tuesday, June 25, 2013, 15:30-16:30.

Venue: Ramanujan Hall

Title: Tame Ramification and Group Cohomology

Speaker:Prof. C. S. Dalawat, Harish-Chandra Research Institute

Abstract: We give an intrinsic parametrisation of the set of tamely ramified extensions of a local field and bring to the fore the role played by group cohomology. We show that two natural definitions of the cohomology class of a tamely ramified finite galoisian extension coincide, and can be recovered from the parameter. We also give an elementary proof of Serre's mass formula in the tame case and in the simplest wild case, and we classify galoisian extensions of degree the cube of a prime (different from the residual characteristic).