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resolvent matrix (Definition)

The resolvent matrix of a matrix $ A$ is defined as

$\displaystyle R_{A}(s)=(sI-A)^{-1}. $

Note: $ I$ is the identity matrix and $ s$ is a complex variable. Also note that $ R_{A}(s)$ is undefined on $ Sp(A)$ (the spectrum of $ A$).

More generally, let $ A$ be a unital algebra over the field of complex numbers $ \mathbb{C}$. The resolvent $ R_x$ of an element $ x\in A$ is a function from $ \mathbb{C}-Sp(x)$ to $ A$ given by

$\displaystyle R_x(s)=(s\cdot 1-x)^{-1} $
where $ Sp(x)$ is the spectrum of $ x$: $ Sp(x)=\lbrace t\in \mathbb{C}\mid t\cdot 1 -x$ is not invertible in $ A\rbrace$.

If $ A$ is commutative and $ s\notin Sp(x)\cup Sp(y)$, then $ R_x(s)-R_y(s)=R_x(s)R_y(s)(x-y)$.



"resolvent matrix" is owned by mps. [ full author list (3) | owner history (1) ]
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Also defines:  resolvent

Attachments:
matrix resolvent properties (Result) by Andrea Ambrosio
resolvent function is analytic (Theorem) by asteroid
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Cross-references: commutative, function, complex numbers, field, algebra, unital, spectrum, variable, complex, identity matrix, matrix
There are 7 references to this entry.

This is version 5 of resolvent matrix, born on 2003-05-01, modified 2006-12-30.
Object id is 4235, canonical name is ResolventMatrix.
Accessed 4201 times total.

Classification:
AMS MSC15A15 (Linear and multilinear algebra; matrix theory :: Determinants, permanents, other special matrix functions)
 47A10 (Operator theory :: General theory of linear operators :: Spectrum, resolvent)

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