请输入您要查询的字词:

 

单词 L1GHasAnApproximateIdentity
释义

L1(G) has an approximate identity


Let G be a locally compact topological group. In general, the Banach *-algebra L1(G) (parent entry (http://planetmath.org/L1GIsABanachAlgebra)) does not have an identity element. In fact:

- L1(G) has an identity element if and only if G is discrete.

When G is discrete the identity element of L1(G) is just the Dirac delta, i.e. the function that takes the value 1 on the identity element of G and vanishes everywhere else.

Nevertheless, L1(G) has always an approximate identity.

Theorem - L1(G) has an approximate identity (eλ)λΛ. Moreover the approximate identity (eλ)λΛ can be chosen to the following :

  • eλ is self-adjoint (http://planetmath.org/InvolutaryRing),

  • eλ1=1,

  • eλCc(G)

where Cc(G) stands for the space of continuous functions G with compact support.

随便看

 

数学辞典收录了18232条数学词条,基本涵盖了常用数学知识及数学英语单词词组的翻译及用法,是数学学习的有利工具。

 

Copyright © 2000-2023 Newdu.com.com All Rights Reserved
更新时间:2025/5/4 22:26:11