Geometric interpolation between Hilbert spaces

Interpolation between Hilbert , Banach and Operator spaces

Motivated by a question of Vincent Lafforgue, we study the Banach spaces X satisfying the following property: there is a function ε → ∆ X (ε) tending to zero with ε > 0 such that every operator T : L 2 → L 2 with T ≤ ε that is simultaneously contractive (i.e. of norm ≤ 1) on L 1 and on L ∞ must be of norm ≤ ∆ X (ε) on L 2 (X). We show that ∆ X (ε) ∈ O(ε α) for some α > 0 iff X is isomorphic to ...

Complex Interpolation between Hilbert, Banach and Operator Spaces

Motivated by a question of Vincent Lafforgue, we study the Banach spaces X satisfying the following property: there is a function ε → ∆ X (ε) tending to zero with ε > 0 such that every operator T : L 2 → L 2 with T ≤ ε that is simultaneously contractive (i.e. of norm ≤ 1) on L 1 and on L ∞ must be of norm ≤ ∆ X (ε) on L 2 (X). We show that ∆ X (ε) ∈ O(ε α) for some α > 0 iff X is isomorphic to ...

Complex Interpolation and Twisted Twisted Hilbert Spaces

The Geometric Tools of Hilbert Spaces

Characterization of splitting for Fréchet-Hilbert spaces via interpolation

Based on the methods from interpolation theory we give a characterization of pairs (E,F ) of Fréchet-Hilbert spaces so that for each Fréchet-Hilbert space G each short exact sequence 0 −→ F −→ G −→ E −→ 0 splits. This characterization essentially depends on a key condition (S) of an interpolation nature. An equivalent description of (S) in terms of appropriate families of interpolation function...