The inverse spectral problem for a Stieltjes eight-shaped string

Abstract

We consider a spectral problem generated by the Stieltjes string equation on a metric figure-of-eight graph and the corresponding inverse problem which is stated as follows. Values of the point masses located on one of the loops and the lengths of subintervals on it are given together with the spectrum of the spectral problem on the whole graph, the total length of the second loop and the length of the first subinterval on it, and a certain constant. Values of the masses and the lengths of subintervals on the second loop are to be found. Conditions sufficient for such a problem to be solvable are given in the implicit form. An algorithm for recovering the masses and the subintervals on the second loop is proposed.