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# Inverse Problems for Various Sturm-Liouville Operators

Abstract (Summary)
In this thesis, we study the inverse nodal problem and inverse spectral problem for various Sturm-Liouville operators, in particular, Hill's operators. We first show that the space of Schr"odinger operators under separated boundary conditions characterized by \${H=(q,al, e)in L^{1}(0,1) imes [0,pi)^{2} : int_{0}^{1}q=0}\$ is homeomorphic to the partition set of the space of all admissible sequences \$X={X_{k}^{(n)}}\$ which form sequences that converge to \$q, al\$ and \$ e\$ individually. The definition of \$Gamma\$, the space of quasinodal sequences, relies on the \$L^{1}\$ convergence of the reconstruction formula for \$q\$ by the exactly nodal sequence. Then we study the inverse nodal problem for Hill's equation, and solve the uniqueness, reconstruction and stability problem. We do this by making a translation of Hill's equation and turning it into a Dirichlet Schr"odinger problem. Then the estimates of corresponding nodal length and eigenvalues can be deduced. Furthermore, the reconstruction formula of the potential function and the uniqueness can be shown. We also show the quotient space \$Lambda/sim\$ is homeomorphic to the space \$Omega={qin L^{1}(0,1) : int_{0}^{1}q = 0, q(x)=q(x+1) mbox{on} mathbb{R}}\$. Here the space \$Lambda\$ is a collection of all admissible sequences \$X={X_{k}^{(n)}}\$ which form sequences that converge to \$q\$. Finally we show that if the periodic potential function \$q\$ of Hill's equation is single-well on \$[0,1]\$, then \$q\$ is constant if and only if the first instability interval is absent. The same is also valid for convex potentials. Then we show that similar statements are valid for single-barrier and concave density functions for periodic string equation. Our result extends that of M. J. Huang and supplements the works of Borg and Hochstadt.
Bibliographical Information:

Advisor:Chiu-Ya Lan; Chun-Kong Law; Chao-Liang Shen; Jenn-Nan Wang; Wei-Cheng Lian; Tzy-Wei Hwang; Chung-Tsun Shieh; Chao-Nien Chen; Tzon-Tzer Lu

School Location:China - Taiwan

Source Type:Master's Thesis

Keywords:sturm liouville problem spectral nodal hill s equation

ISBN:

Date of Publication:07/04/2005

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