 Operator theory

In mathematics, operator theory is the branch of functional analysis that focuses on bounded linear operators, but which includes closed operators and nonlinear operators.
Operator theory also includes the study of algebras of operators.
Contents
Single operator theory
Single operator theory deals with the properties and classification of single operators. For example, the classification of normal operators in terms of their spectra falls into this category.
Operator algebras
The theory of operator algebras brings algebras of operators such as C*algebras to the fore.
See also
 Invariant subspace
 Functional calculus
 Spectral theory
 Compact operator
 Fredholm theory of integral equations
 Integral operator
 Fredholm operator
 Fredholm theory of integral equations
 Selfadjoint operator
 Unbounded operator
 Umbral calculus
 Contraction mapping
 Positive operator on a Hilbert space
 Nonnegative operator on a partially ordered vector space
External links
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