An inverse problem on a metric graph with cycle

TL;DR

This paper addresses an inverse spectral problem on a quantum graph with a cycle, demonstrating how to determine edge lengths and potentials from spectral and boundary derivative data.

Contribution

It introduces a method to recover edge lengths and potentials on a cyclic quantum graph using spectral data and boundary derivatives, expanding inverse problem techniques.

Findings

Successfully reconstructs edge lengths and potentials from spectral data.

Provides a new approach for inverse problems on cyclic quantum graphs.

Enhances understanding of spectral data's role in quantum graph reconstruction.

Abstract

Consider a quantum graph consisting of a ring with two attached edges, and assume Kirchhoff-Neumann conditions hold at the internal vertices. Associated to this graph is a Schr\"{o}dinger type operator $L=-\Delta +q(x)$ with Dirichlet boundary conditions at the two boundary nodes. Let $\{ \omega_n^2, \ \varphi_n(x)\}$ be the eigenvalues and associated normalized eigenfunctions. Let $v_1$ be a boundary vertex, and $v_2$ the adjacent internal vertex. Assume we know the following data: $\{ \omega_n^2,\partial_x \varphi_n(v_1),\partial_x\varphi_n(v_2)\}.$ Here $\partial_x\varphi_n(v_2)$ refers to an outward normal derivative at $v_2$ along one of the edges incident to the other internal vertex. From this data we determine the following unknown quantities: the lengths of edges and the potential functions on each edge.