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Nov 18, 2022 at 7:35 vote accept Guido Li
Nov 17, 2022 at 19:01 history edited Jochen Glueck CC BY-SA 4.0
added 3 characters in body
Nov 17, 2022 at 18:53 comment added Willie Wong Thank you very much for the expanded discussion, and for pointing out your PhD Thesis with its very useful appendix.
Nov 17, 2022 at 18:27 comment added Jochen Glueck By the way, I'd suspect more generally that the following statements are equivalent for any pole $\lambda$ of the resolvent of a linear operator: (i) The eigenvalue $\lambda$ is semi-simple; (ii) The eigenspace of $\lambda$ separates the dual eigenspace; (iii) the dual eigenspace separates the eigenspace; (iv) the eigenspace and the dual eigenspace separate each other. But admittedly, I haven't thought about it in too much detail, yet, so currently I'm not completely sure whether this characterization is indeed correct.
Nov 17, 2022 at 18:22 comment added Jochen Glueck @GuidoLi: Thanks for your response. I've now added various details.
Nov 17, 2022 at 18:22 comment added Jochen Glueck @WillieWong: Sorry for the delay. I've added many details, and discussed a few references in the end. I hope it's easier to follow the argument now.
Nov 17, 2022 at 18:21 history edited Jochen Glueck CC BY-SA 4.0
I added a lot of details to the answer.
Nov 16, 2022 at 23:41 comment added Guido Li @JochenGlueck thanks jochen for your answer, I admit i would also like to hear a bit more about why the projections what you call 'separate' each other...
Nov 16, 2022 at 17:31 comment added Jochen Glueck @WillieWong: Sorry for the confusion! I'm on a bus right now (with just my mobile phone and no books), but I'll add some references and explanations later.
Nov 16, 2022 at 17:30 comment added Jochen Glueck @GiorgioMetafune: Yes, in the sense that Willie Wong mentions.
Nov 16, 2022 at 17:27 comment added Willie Wong I find myself too poorly educated to understand how any single sentence in the proof goes. Do you have a reference that I can look at for this?
Nov 16, 2022 at 17:21 comment added Willie Wong I think (but not sure) it means given any $v \neq w$ in $\ker(\lambda - T)$ you can find $x$ in $\ker(\bar{\lambda} - T^*)$ such that $x(v)\neq x(w)$; and vice versa. @GiorgioMetafune
Nov 16, 2022 at 17:16 comment added Giorgio Metafune What you mean by "separate each other"?
Nov 16, 2022 at 16:59 history answered Jochen Glueck CC BY-SA 4.0