# On coupling constant thresholds in one dimension

## TL;DR

This paper investigates how the thresholds for negative eigenvalues of one-dimensional Schrödinger operators depend on coupling constants and potential scaling, providing asymptotic formulas for bound states as parameters vary.

## Contribution

It introduces new asymptotic formulas for bound states in one-dimensional Schrödinger operators with scaled potentials, extending understanding of threshold behaviour.

## Key findings

- Asymptotic formulas for bound states are derived.
- Explicit first-order terms are computed for various potential scaling limits.
- Conditions for the existence of bound states at the spectrum threshold are established.

## Abstract

The threshold behaviour of negative eigenvalues for Schr\"{o}dinger operators of the type $$ H_\lambda=-\frac{d^2}{dx^2}+U(x)+\lambda\alpha_\lambda V(\alpha_\lambda x) $$ is considered. The potentials $U$ and $V$ are real-valued bounded functions of compact support, $\lambda$ is a positive parameter, and positive sequence $\alpha_\lambda$ has a finite or infinite limit as $\lambda\to 0$. Under certain conditions on the potentials there exists a bound state of $H_\lambda$ which is absorbed at the bottom of the continuous spectrum. For several cases of the limiting behaviour of sequence $\alpha_\lambda$, asymptotic formulas for the bound states are proved and the first order terms are computed explicitly.