# Approximation of magnetic Schrödinger operators with δ-interactions supported on networks

## TL;DR

This paper studies how to approximate a complex magnetic Schrödinger operator with a singular potential using simpler operators in a mathematically rigorous way.

## Contribution

The paper provides a norm resolvent approximation for magnetic Schrödinger operators with δ-interactions on networks under minimal assumptions.

## Key findings

- The approximation is valid for Σ being a finite union of C²-hypersurfaces or a graph in R².
- The convergence result holds even when coefficients are complex-valued.
- Spectral implications of the convergence are analyzed.

## Abstract

This paper deals with the approximation of a magnetic Schrödinger operator with a singular \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta $$\end{document}δ-potential that is formally given by \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$(i \nabla + A)^2 + Q + \alpha \delta _\Sigma $$\end{document}(i∇+A)2+Q+αδΣ by Schrödinger operators with regular potentials in the norm resolvent sense. This is done for \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\Sigma $$\end{document}Σ being the finite union of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$C^2$$\end{document}C2-hypersurfaces, for coefficients A, Q, and \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\alpha $$\end{document}α under almost minimal assumptions such that the associated quadratic forms are closed and sectorial, and Q and \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\alpha $$\end{document}α are allowed to be complex-valued functions. In particular, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\Sigma $$\end{document}Σ can be a graph in \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathbb {R}^2$$\end{document}R2 or the boundary of a piecewise \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$C^2$$\end{document}C2-domain. Moreover, spectral implications of the mentioned convergence result are discussed.