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Difference between revisions of "Indefinite metric"

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A term used in the theory of spaces with an indefinite metric (cf. [[Space with an indefinite metric|Space with an indefinite metric]]) for denoting (depending on the type of space) either a [[Bilinear form|bilinear form]], a [[Sesquilinear form|sesquilinear form]] or a (non-linear) functional of a certain degree of homogeneity, defined on the space under consideration. An indefinite metric is not a metric (that is, a distance), and the epithet  "indefinite"  means that either the sesquilinear form is not positive definite or the functional is not a power of a norm on the space. The various types of indefinite metrics are called <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/i/i050/i050570/i0505701.png" />-metric, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/i/i050/i050570/i0505702.png" />-metric, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/i/i050/i050570/i0505703.png" />-metric (see [[Hilbert space with an indefinite metric|Hilbert space with an indefinite metric]]; [[Pontryagin space|Pontryagin space]]).
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A term used in the theory of spaces with an indefinite metric (cf. [[Space with an indefinite metric|Space with an indefinite metric]]) for denoting (depending on the type of space) either a [[Bilinear form|bilinear form]], a [[Sesquilinear form|sesquilinear form]] or a (non-linear) functional of a certain degree of homogeneity, defined on the space under consideration. An indefinite metric is not a metric (that is, a distance), and the epithet  "indefinite"  means that either the sesquilinear form is not positive definite or the functional is not a power of a norm on the space. The various types of indefinite metrics are called $G$-metric, $I$-metric, $J$-metric (see [[Hilbert space with an indefinite metric|Hilbert space with an indefinite metric]]; [[Pontryagin space|Pontryagin space]]).

Latest revision as of 10:45, 16 April 2014

A term used in the theory of spaces with an indefinite metric (cf. Space with an indefinite metric) for denoting (depending on the type of space) either a bilinear form, a sesquilinear form or a (non-linear) functional of a certain degree of homogeneity, defined on the space under consideration. An indefinite metric is not a metric (that is, a distance), and the epithet "indefinite" means that either the sesquilinear form is not positive definite or the functional is not a power of a norm on the space. The various types of indefinite metrics are called $G$-metric, $I$-metric, $J$-metric (see Hilbert space with an indefinite metric; Pontryagin space).

How to Cite This Entry:
Indefinite metric. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Indefinite_metric&oldid=18743
This article was adapted from an original article by A.I. Shtern (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article