Generalisations and Alternative Approaches
A Weyl function can be defined at a singular endpoint giving rise to a singular version of Weyl–Titchmarsh–Kodaira theory. this applies for example to the case of radial Schrödinger operators
The whole theory can also be extended to the case where the coefficients are allowed to be measures.
Read more about this topic: Spectral Theory Of Ordinary Differential Equations
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