Inverse problems in spectral theory address the challenge of reconstructing differential operators from observed spectral data. This field, rich in both theoretical and applied mathematics, underpins ...

The spectrum of the canonical operator in the noncommutative 2-torus Tθ depending on the parameter θ ∈ [0,1] © Douglas Hofstadter's butterfly. Licensed under ...

Let T = H + iK be hyponormal and 𝜑 be a strictly monotone increasing continuous function on σ(H). We define $\tilde{\varphi}(T)$ by $\tilde{\varphi}(T)=\varphi (H)+iK$. In this paper, we show that if ...

Spectral problems in boundary value problems constitute a fundamental area of applied mathematics and mathematical physics, where the focus lies on determining eigenvalues and corresponding ...