J-invariant of linear algebraic groups and Tits algebras

The J-invariant of a linear algebraic group measures the subring of rational cycles on the variety of its Borel subgroups. In the talk I’m going to introduce this invariant and discuss its possible values. The restrictions come from Steenrod operations and from indices of Tits algebras. If time permits, I will discuss applications of the J-invariant to cohomological invariants of algebraic groups.