Abstract

We give here a model-theoretical solution to the problem, raised by J.L: Krivine, of the consistency of λβη+U(G)+Ω=t, wheret is an arbitrary λ-term,G an arbitrary finite group of order, sayn, andU(G) the theory which expresses the existence of a surjectiven-tuple notion, such that each element ofG behaves simultaneously as a permutation of the components of then-tuple and as an automorphism of the model. This provides in particular a semantic proof of the βη-easiness of the λ-term Ω