TY - JOUR ID - Turner2020 LB - Turner2020 AU - Turner, John Wm. TI - Echoes and glimpses of a distant drum ST - Echoes and glimpses of a distant drum JO - Opuscula Math. JA - Opuscula Math. JF - Opuscula Mathematica PY - 2020 VL - 40 IS - 6 SP - 737 EP - 750 DO - https://doi.org/10.7494/OpMath.2020.40.6.737 UR - https://doi.org/10.7494/OpMath.2020.40.6.737 AB - To what extent does the spectrum of the Laplacian operator on a domain \(D\) with prescribed boundary conditions determine its shape? This paper first retraces the history of this problem, then Kac's approach in terms of a diffusion process with absorbing boundary conditions. It is shown how the restriction to a polygonal boundary for \(D\) in this method, which required taking the limit of an infinite number of sides to obtain a smooth one, can be avoided by using the Duhamel method. KW - Kac drum problem KW - inverse methods KW - diffusion process SN - 1232-9274 ER -