Essential dimension of cohomology classes via valuation theory
摘要
We give a formula for the essential dimension of a cohomology class α in Hd(K, ℚp/ℤp(d)) when K is a strictly Henselian field. This formula is particularly explicit in the case where α is a Brauer class (for d = 2). As an application of our bound with d = 3, we study the essential dimension of exceptional groups by examining the image of the Rost invariant.