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Schrodinger operators, operators on manifolds, general differential operators, numerical studies, integral operators, discrete models, resonances, non-self-adjoint operators, random operators/matrices

3 votes
Accepted

Leibniz rule for square root of Laplacian

For the Leibniz rule, it is not true that \begin{equation} (-\Delta)^{\frac12}(fg) = f (-\Delta)^{\frac12}g + g (-\Delta)^{\frac12}f \end{equation} even in the simplest possible case, i.e. in $\mathbb …
an_ordinary_mathematician's user avatar
4 votes
Accepted

Is the spectrum of a "self adjoint" operator real on $\ell^p$?

It seems that I have found a counter example myself. For the Hilbert matrix $$ H_\lambda:= \big( \frac{1}{1-\lambda+k+n} \big)_{k,n\geq 0}, \lambda < 1 $$ Rosenblum in "On the Hilbert Matrix I, Pro …
an_ordinary_mathematician's user avatar
11 votes
1 answer
465 views

Is the spectrum of a "self adjoint" operator real on $\ell^p$?

There might be an obvious answer to the question, but it doesn't come to mind. Suppose we have an infinite matrix $A=(a_{ij})$, which defines a bounded linear operator on $\ell^p$, i.e. for all seque …