Volume 5, Issue 1
Hearing the Triangles: A Numerical Perspective

Wei Gong, Xiaodong Liu & Jing Wang

CSIAM Trans. Appl. Math., 5 (2024), pp. 58-72.

Published online: 2024-02

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  • Abstract

We introduce a two-step numerical scheme for reconstructing the shape of a triangle by its Dirichlet spectrum. With the help of the asymptotic behavior of the heat trace, the first step is to determine the area, the perimeter, and the sum of the reciprocals of the angles of the triangle. The shape is then reconstructed, in the second step, by an application of the Newton’s iterative method or the Levenberg-Marquardt algorithm for solving a nonlinear system of equations on the angles. Numerically, we have used only finitely many eigenvalues to reconstruct the triangles. To our best knowledge, this is the first numerical simulation for the classical inverse spectrum problem in the plane. In addition, we give a counter example to show that, even if we have infinitely many eigenvalues, the shape of a quadrilateral may not be heard.

  • AMS Subject Headings

35P15, 35P20, 35J05, 35P99

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COPYRIGHT: © Global Science Press

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@Article{CSIAM-AM-5-58, author = {Gong , WeiLiu , Xiaodong and Wang , Jing}, title = {Hearing the Triangles: A Numerical Perspective}, journal = {CSIAM Transactions on Applied Mathematics}, year = {2024}, volume = {5}, number = {1}, pages = {58--72}, abstract = {

We introduce a two-step numerical scheme for reconstructing the shape of a triangle by its Dirichlet spectrum. With the help of the asymptotic behavior of the heat trace, the first step is to determine the area, the perimeter, and the sum of the reciprocals of the angles of the triangle. The shape is then reconstructed, in the second step, by an application of the Newton’s iterative method or the Levenberg-Marquardt algorithm for solving a nonlinear system of equations on the angles. Numerically, we have used only finitely many eigenvalues to reconstruct the triangles. To our best knowledge, this is the first numerical simulation for the classical inverse spectrum problem in the plane. In addition, we give a counter example to show that, even if we have infinitely many eigenvalues, the shape of a quadrilateral may not be heard.

}, issn = {2708-0579}, doi = {https://doi.org/10.4208/csiam-am.SO-2023-0027}, url = {http://global-sci.org/intro/article_detail/csiam-am/22920.html} }
TY - JOUR T1 - Hearing the Triangles: A Numerical Perspective AU - Gong , Wei AU - Liu , Xiaodong AU - Wang , Jing JO - CSIAM Transactions on Applied Mathematics VL - 1 SP - 58 EP - 72 PY - 2024 DA - 2024/02 SN - 5 DO - http://doi.org/10.4208/csiam-am.SO-2023-0027 UR - https://global-sci.org/intro/article_detail/csiam-am/22920.html KW - Inverse spectral problems, Newton iteration, Vandermonde matrix, ill-posedness, triangles. AB -

We introduce a two-step numerical scheme for reconstructing the shape of a triangle by its Dirichlet spectrum. With the help of the asymptotic behavior of the heat trace, the first step is to determine the area, the perimeter, and the sum of the reciprocals of the angles of the triangle. The shape is then reconstructed, in the second step, by an application of the Newton’s iterative method or the Levenberg-Marquardt algorithm for solving a nonlinear system of equations on the angles. Numerically, we have used only finitely many eigenvalues to reconstruct the triangles. To our best knowledge, this is the first numerical simulation for the classical inverse spectrum problem in the plane. In addition, we give a counter example to show that, even if we have infinitely many eigenvalues, the shape of a quadrilateral may not be heard.

Wei Gong, Xiaodong Liu & Jing Wang. (2024). Hearing the Triangles: A Numerical Perspective. CSIAM Transactions on Applied Mathematics. 5 (1). 58-72. doi:10.4208/csiam-am.SO-2023-0027
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