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Interior product

 
Wikipedia: Interior product

In mathematics, the interior product is a degree −1 antiderivation on the exterior algebra of differential forms on a smooth manifold. It is defined to be the contraction of a differential form with a vector field. Thus if X is a vector field on the manifold M, then

\iota_X\colon \Omega^p(M) \to \Omega^{p-1}(M)

is the map which sends a p-form ω to the (p−1)-form iXω defined by the property that

( \iota_X\omega )(X_1,\ldots,X_{p-1})=\omega(X,X_1,\ldots,X_{p-1})

for any vector fields X1,..., Xp−1.

The interior product is also called interior or inner multiplication, or the inner derivative or derivation. The interior product ιX ω is sometimes written as X ω; this chracter is U+2A3C in Unicode.

The interior product is the unique antiderivation of degree −1 on the exterior algebra such that on one-forms α

ιXα = α(X),

the duality pairing between α and the vector X. Explicitly, if β is a p-form and γ is a q-form, then

 \iota_X(\beta\wedge\gamma) = (\iota_X\beta)\wedge\gamma+(-1)^p\beta\wedge(\iota_X\gamma).

Properties

By antisymmetry,

 \iota_X \iota_Y \omega = - \iota_Y \iota_X^{ } \omega

and so  \iota_X^2 = 0 . The interior product relates the exterior derivative and Lie derivative of differential forms by Cartan's identity:

 \mathcal L_X\omega = \mathrm d (\iota_X \omega) + \iota_X \mathrm d\omega.

This identity is important in symplectic geometry: see moment map.

See also



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Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Interior product" Read more