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math.AP2018
Sturm's theorem on the zeros of sums of eigenfunctions: Gelfand's strategy implemented
Pierre Bérard, Bernard Helffer
In the second section "Courant-Gelfand theorem" of his last published paper (Topological properties of eigenoscillations in mathematical physics, Proc. Steklov Institute Math. 273…
math.AP2014★ 10 cited
Dirichlet eigenfunctions of the square membrane: Courant's property, and A. Stern's and Å. Pleijel's analyses
Pierre Bérard, Bernard Helffer
In this paper, we revisit Courant's nodal domain theorem for the Dirichlet eigenfunctions of a square membrane, and the analyses of A. Stern and Å. Pleijel.