"L^2_loc mod constants" as a reflexive space - MathOverflow

"L^2_loc mod constants" as a reflexive space

2011-05-17T09:09:11Z

In an article of Sten Kaijser ("A note on dual Banach spaces") I find the assertion that $E = L^2_{\text{loc}}({\mathbb R})$ modulo constants is a reflexive space.

Question 1: which is the 'natural' locally convex top. vector space structure of this space? (maybe the proj. limit of $L^2(K_n)$-spaces modulo constants where $(K_n)_{n\ge 1}$ exhausts ${\mathbb R}$ compactly?).

Question 2: How can I see reflexivity of $E$?

Answer by Piero D'Ancona for "L^2_loc mod constants" as a reflexive space

2011-05-17T09:53:38Z

I'd say the natural structure on $E$ is one of a Frechet space, given by the family of seminorms $\|f\|_{L^2(K_n)}$. Each local space generated by each seminorm is reflexive (Hilbert) so the resulting topology is reflexive. Then if you take the quotient by the closed subspace of constant functions you get again a reflexive space. Details in this nice set of lectures by Dietmar Vogt.