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Difference between revisions of "Lie bracket"

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The commutator of vector fields (cf. [[Vector field on a manifold|Vector field on a manifold]]) on a [[Differentiable manifold|differentiable manifold]]. If one interprets vector fields of class <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585501.png" /> on a differentiable (of class <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585502.png" />) manifold <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585503.png" /> as derivations of the algebra <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585504.png" /> of functions of class <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585505.png" /> on <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585506.png" />, then the Lie bracket of the fields <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585507.png" /> and <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585508.png" /> is given by the formula
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The commutator of vector fields (cf. [[Vector field on a manifold|Vector field on a manifold]]) on a [[Differentiable manifold|differentiable manifold]]. If one interprets vector fields of class $C^\infty$ on a differentiable (of class $C^\infty$) manifold $M$ as derivations of the algebra $F(M)$ of functions of class $C^\infty$ on $M$, then the Lie bracket of the fields $X$ and $Y$ is given by the formula
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l0585509.png" /></td> </tr></table>
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$$[X,Y]f=X(Yf)-Y(Xf),$$
  
where <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l05855010.png" />. The totality of all vector fields of class <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l05855011.png" /> on <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l058/l058550/l05855012.png" /> is a [[Lie algebra|Lie algebra]] with respect to the Lie bracket.
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where $f\in F(M)$. The totality of all vector fields of class $C^\infty$ on $M$ is a [[Lie algebra|Lie algebra]] with respect to the Lie bracket.
  
  

Latest revision as of 15:04, 13 April 2014

The commutator of vector fields (cf. Vector field on a manifold) on a differentiable manifold. If one interprets vector fields of class $C^\infty$ on a differentiable (of class $C^\infty$) manifold $M$ as derivations of the algebra $F(M)$ of functions of class $C^\infty$ on $M$, then the Lie bracket of the fields $X$ and $Y$ is given by the formula

$$[X,Y]f=X(Yf)-Y(Xf),$$

where $f\in F(M)$. The totality of all vector fields of class $C^\infty$ on $M$ is a Lie algebra with respect to the Lie bracket.


Comments

The Lie bracket of two vector fields can also be viewed as the Lie derivative of one vector field in the direction of the other.

How to Cite This Entry:
Lie bracket. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Lie_bracket&oldid=11467
This article was adapted from an original article by A.L. Onishchik (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article