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Difference between revisions of "Lattice in a Lie group"

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A [[Discrete subgroup|discrete subgroup]] <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576501.png" /> of a [[Lie group|Lie group]] <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576502.png" /> such that <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576503.png" /> has a finite volume relative to the (induced) <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576504.png" />-invariant measure.
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A [[Discrete subgroup|discrete subgroup]] $\Gamma$ of a [[Lie group|Lie group]] $G$ such that $G/\Gamma$ has a finite volume relative to the (induced) $G$-invariant measure.
  
A lattice of dimension <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576506.png" /> (or rank) <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576508.png" /> in a vector space <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l0576509.png" /> over <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765010.png" /> or <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765011.png" /> is a free Abelian subgroup in <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765012.png" /> generated by <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765013.png" /> linearly independent vectors over <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765014.png" />. A subgroup of the additive group of a finite-dimensional vector space <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765015.png" /> over <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l057/l057650/l05765016.png" /> is discrete if and only if it is a lattice [[#References|[1]]].
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A lattice of dimension $n$ (or rank) $n$ in a vector space $V$ over $\mathbf R$ or $\mathbf C$ is a free Abelian subgroup in $V$ generated by $n$ linearly independent vectors over $\mathbf R$. A subgroup of the additive group of a finite-dimensional vector space $V$ over $\mathbf R$ is discrete if and only if it is a lattice [[#References|[1]]].
  
 
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Revision as of 14:15, 10 August 2014

A discrete subgroup $\Gamma$ of a Lie group $G$ such that $G/\Gamma$ has a finite volume relative to the (induced) $G$-invariant measure.

A lattice of dimension $n$ (or rank) $n$ in a vector space $V$ over $\mathbf R$ or $\mathbf C$ is a free Abelian subgroup in $V$ generated by $n$ linearly independent vectors over $\mathbf R$. A subgroup of the additive group of a finite-dimensional vector space $V$ over $\mathbf R$ is discrete if and only if it is a lattice [1].

References

[1] S.A. Morris, "Pontryagin duality and the structure of locally compact Abelian groups" , London Math. Soc. Lecture Notes , 29 , Cambridge Univ. Press (1977)


Comments

See also Discrete group of transformations.

How to Cite This Entry:
Lattice in a Lie group. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Lattice_in_a_Lie_group&oldid=11363
This article was adapted from an original article by r group','../u/u095350.htm','Unitary transformation','../u/u095590.htm','Vector bundle, analytic','../v/v096400.htm')" style="background-color:yellow;">A.L. Onishchik (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article