© 2004 by London Mathematical Society
© The London Mathematical Society
On the Uniqueness of the Algebraic Multiplicity
Departamento de Matemática Aplicada, Universidad Complutense de Madrid 28040-Madrid, Spain, carlos_mora{at}mat.ucm.es
Received 31 January 2003. Revision received 14 May 2003.
Given a smooth family £ of real or complex variable taking values within the class of Fredholm operators of index zero in a Banach space, there are some available definitions in the literature of the concept of algebraic multiplicity of the family £ at a point x0 of the parameter at which the operator L(x0) becomes non-invertible. The purpose of the paper is to show that the algebraic multiplicity is uniquely determined by a few of its properties, independently of its construction. The main technical tools to obtain this uniqueness result are a LyapunovSchmidt reduction, the local Smith form and a new factorization result for general families at non-algebraic eigenvalues obtained in the paper.