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A Hilbert space $H$ is a real or complex vector space endowed with an inner product such that $H$ is a complete metric space when endowed with the norm induced by this inner product.

5 votes
1 answer
177 views

An extension of Lomonosov Theorem

Let $H$ be a complex infinite dimensional separable Hilbert space. There are various extensions of the following well known result: Theorem (Lomonosov): Every nonscalar $T \in B(H)$ which commutes wi …
Manuel Norman's user avatar
3 votes
0 answers
391 views

On a possible attempt to prove the invariant subspace problem

This question involves a possible method to prove the invariant subspace problem for (separable) infinite dimensional Hilbert spaces. The idea comes from various results on this topic; more precisely, …
Manuel Norman's user avatar
1 vote
Accepted

An extension of Lomonosov Theorem

Looking again at Solution 12.4 in Kubrusly's book, I have noticed that the proof can be used even to prove the statement above, with some small changes. I will briefly sketch such small modifications: …
Manuel Norman's user avatar
1 vote
0 answers
26 views

On some bounds on two constants concerning the disconnectedness of the spectra of small pert...

Let $H$ be a separable, infinite dimensional, complex Hilbert space. In the book: Jiang, C. L.; Wang, Z. Y. (1998). Strongly Irreducible Operators on Hilbert Space. CRC press above the statement of Th …
Manuel Norman's user avatar