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On the reflection law for the Helmholtz equation. (English. Russian original) Zbl 0807.35024
Sov. Math., Dokl. 45, No. 1, 42-45 (1992); translation from Dokl. Akad. Nauk SSSR 322, No. 1, 48-51 (1992).
This article presents a new reflection formula for solutions to the two dimensional homogeneous Helmholtz equation. This formula connects values of the solution $$u(x,y)$$ in domains $${\mathcal U}_ 1$$ and $${\mathcal U}_ 2$$ which are separated by a real analytic curve and is a generalization of the classical Schwartz symmetry principle.
Reviewer: P.Zabreiko (Minsk)

##### MSC:
 35J05 Laplace operator, Helmholtz equation (reduced wave equation), Poisson equation
##### Keywords:
reflection formula; Schwartz symmetry principle