Eigenvectors from Eigenvalues

[nikol]

Must be very handy...



https://arxiv.org/abs/1908.03795



Discoveries are still made.



I got it from this article

https://www.quantamagazine.org/neutrinos-lead-to-unexpected-discovery-in-basic-math-20191113/

[mtsm]

Saw that, quite romantic I must say...

[nikol]

Forgot to update. Thanks.



It appears that this result is known

(in russian): "Calculation of eigenvalues and eigenvectors in mesh-type problems (Algorithms and error estimations)" (1986)

http://math.ucdenver.edu/~aknyazev/research/papers/old/k.pdf



and there the following is referenced:

"Error bounds in Rayleigh-Ritz approximation of eigenvectors" (1934)

https://pdfs.semanticscholar.org/dd58/71b7a8e6c07071bc04e483c09841919f80e3.pdf



so, thanks to social media for popping up the subject

[zee4]

Did he write the equations by hand? Or is it 80's LaTeX?

[nikol]

As far as I remember 90% of university preprints in soviet times were with handwriting formulas.