文摘
It is well known that a spherically symmetric wave speed problem in a bounded spherical region may be reduced, by means of Liouville transform, to the Sturm–Liouville problem B(a;q)B(a;q) in [0,1][0,1]. We prove that a twin dense subset of the nodal set in a subinterval (⊂[0,1]⊂[0,1]) uniquely determines the potential qq on the whole interval [0,1][0,1] and the boundary parameter aa. The method employed is to convert the inverse nodal problem into the inverse spectral problem with partial information given on the potential on a subinterval.