Damascelli, Lucio On the nodal set of the second eigenfunction of the Laplacian in symmetric domains \(\mathbb R^N \). (English) Zbl 1042.35036 Atti Accad. Naz. Lincei, Cl. Sci. Fis. Mat. Nat., IX. Ser., Rend. Lincei, Mat. Appl. 11, No. 3, 175-181 (2000). A previous conjecture concerning the eigenfunctions of the Laplacian in a domain \(\Omega\in\mathbb R^N \) is considered: if \(\Omega\) is connected and symmetric with respect to \(k\) orthogonal directions, then the nodal set of the eigenfunctions must intersect the boundary. The proof is given by using some symmetry properties of the eigenfunctions and the maximum principle. For \(N=2,\,k=1\) the result was proved in L. E. Payne [Z. Angew. Math. Phys. 24, 721–729 (1973; Zbl 0272.35058)]. Some resuls concerning the periodic solutions of the Laplacian in symmetric domains are given in J. F. Bourgat [ Rapport I.R.I.A., Roquencourt, France (1978)]. Reviewer: Gelu Pasa (Bucharest) Cited in 8 Documents MSC: 35P05 General topics in linear spectral theory for PDEs 35A30 Geometric theory, characteristics, transformations in context of PDEs Keywords:second eigenfunction; Nodal set; Maximum principle. Citations:Zbl 0272.35058 PDFBibTeX XMLCite \textit{L. Damascelli}, Atti Accad. Naz. Lincei, Cl. Sci. Fis. Mat. Nat., IX. Ser., Rend. Lincei, Mat. Appl. 11, No. 3, 175--181 (2000; Zbl 1042.35036)