
 PlanetMath: eigenvalue 
  Eigenvalues are of relatively little importance in connection with an infinitedimensional vector space, unless that space is endowed with some additional structure, typically that of a Banach space or Hilbert space. 
  Crossreferences: Hilbert space, Banach space, structure, infinitedimensional, conjugate, real, eigenvalue problem, variations, even, roots, determinants, matrix, basis, odd, algebraically closed, characteristic polynomial, variable, degree, polynomial, finite, map, operations, obvious, complex numbers, sequences, complex, dimension, infinite, surjective, injective, inverse, equivalent, linear algebra, finite dimensional, action, vector, scalar, linear mapping, Endomorphism, field, vector space 
  This is version 11 of eigenvalue, born on 20020119, modified 20060609. 
 planetmath.org /encyclopedia/Eigenvalue.html (301 words) 
