The strong linkage principle.
We develop a new approach of extension calculus in the category of strict polynomial functors, based on Troesch complexes. We obtain new short elementary proofs of numerous classical -computations as well as new results. In particular, we get a cohomological version of the “fundamental theorems” from classical invariant theory for for big enough (and we give a conjecture for smaller values of ). We also study the “twisting spectral sequence” converging to the extension groups between the...
We classify quadratic - and -modules by crude computation, generalising in the first case a Theorem proved independently by F.G. Timmesfeld and S. Smith. The paper is the first of a series dealing with linearisation results for abstract modules of algebraic groups and associated Lie rings.