Bessaga's conjecture in unstable Köthe spaces and products
Let F be a complemented subspace of a nuclear Fréchet space E. If E and F both have (absolute) bases resp. , then Bessaga conjectured (see [2] and for a more general form, also [8]) that there exists an isomorphism of F into E mapping to where is a scalar sequence, π is a permutation of ℕ and is a subsequence of ℕ. We prove that the conjecture holds if E is unstable, i.e. for some base of decreasing zero-neighborhoods consisting of absolutely convex sets one has ∃s ∀p ∃q ∀r where...