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1	The degree theory and the index of a critical point for mappings of the type (<em>S</em><sub>+</sub>) Oinas, J. (Janne) 31 May 2007 (has links) Abstract The dissertation considers a degree theory and the index of a critical point of demi-continuous, everywhere defined mappings of the monotone type. A topological degree is derived for mappings from a Banach space to its dual space. The mappings satisfy the condition (S+), and it is shown that the derived degree has the classical properties of a degree function. A formula for the calculation of the index of a critical point of a mapping A : X→X* satisfying the condition (S+) is derived without the separability of X and the boundedness of A. For the calculation of the index, we need an everywhere defined linear mapping A' : X→X* that approximates A in a certain set. As in the earlier results, A' is quasi-monotone, but our situation differs from the earlier results because A' does not have to be the Frechet or Gateaux derivative of A at the critical point. The theorem for the calculation of the index requires a construction of a compact operator T = (A' + Γ)-1Γ with the aid of linear mappings Γ : X→X and A'. In earlier results, Γ is compact, but here it need only be quasi-monotone. Two counter-examples show that certain assumptions are essential for the calculation of the index of a critical point. Brouwer degree Browder degree Leray-Schauder theory Skrypnik degree degree theory index of a critical point index of a singular point mapping degree mappings of monotone type nonlinear analysis nonlinear functional analysis rotation of vector field the Brouwer-Hopf theory the Browder theory the Leray-Schauder degree the Skrypnik theory topological degree

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The degree theory and the index of a critical point for mappings of the type (<em>S</em><sub>+</sub>)