Bounds on Multiplicities of Laplace-Beltrami Operator Eigenvalues on the   Real Projective Plane
  The known upper bounds for the multiplicities of the Laplace-Beltrami operator eigenvalues on the real projective plane are improved for the eigenvalues with even indexes. Upper bounds for Dirichlet, Neumann and Steklov eigenvalues on the real projective plane with holes are also provided. 
Aleksandr S. Berdnikov, Nikolai S. Nadirashvili, Alexei V. Penskoi
math.DG math.SP