Breit–Wigner series convergence conjecture for super-exponentially decreasing potentials

Let VV be a super-exponentially decreasing potential, meaning that for every NNN\in\mathbf{N}, V(x)NeNx|V(x)|\lesssim_N e^{-N|x|}. Its Breit–Wigner series is

B(V)=λResV{0}Imλλ2.B(V)=-\sum_{\lambda\in\operatorname{Res}V\setminus\{0\}}\frac{\operatorname{Im}\lambda}{|\lambda|^2}.

Breit–Wigner convergence conjecture. The series B(V)B(V) converges if and only if VV is compactly supported.

For compactly supported potentials the series converges, while the conjecture predicts divergence for every super-exponentially decreasing potential that is not compactly supported. This would provide the expected cancellation of infinities in the Breit–Wigner formula as the support becomes unbounded.

Sources & referencesView supporting material

Primary source

Aidan Backus, “The Breit-Wigner series for noncompactly supported potentials on the line”, arXiv:2005.13765 (2020).

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