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Nonstandard Ideals from Nonstandard Dual Pairs for $L^1(omega)$ and $l^1(omega)$

机译:来自非标准对的非标准理想,价格为$ L ^ 1(omega)$和$ l ^ 1(omega)$

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The Banach convolution algebras $l^1(omega)$and their continuous counterparts $L^1(R^+,omega)$are muchstudied, because (when the submultiplicative weight function$omega$ is radical) they are pretty much the prototypic examplesof commutative radical Banach algebras. In cases of ``nice''weights $omega$, the only closed ideals they have are the obvious,or ``standard'', ideals. But in thegeneral case, a brilliant but very difficult paper of Marc Thomasshows that nonstandard ideals exist in $l^1(omega)$. Hisproof was successfully exported to the continuous case$L^1(R^+,omega)$ by Dales and McClure, but remaineddifficult. In this paper we first present a small improvement: anew and easier proof of the existence of nonstandard ideals in$l^1(omega)$ and $L^1(R^+,omega)$. The new proof is based onthe idea of a ``nonstandard dual pair'' which we introduce.We are then able to make a much larger improvement: wefind nonstandard ideals in $L^1(R^+,omega)$ containing functionswhose supports extend all the way down to zero in $R^+$, thereby solvingwhat has become a notorious problem in the area.
机译:Banach卷积代数$ l ^ 1(omega)$和它们的连续对等代数$ L ^ 1(R ^ +,omega)$被研究了很多,因为(当次乘权函数$ omega $是基数时)它们是原型可交换根Banach代数的例子在``好''的权重$ omega $的情况下,它们仅有的封闭理想是显而易见的或``标准''理想。但是在一般情况下,马克·托马斯(Marc Thomas)的一篇精彩而非常困难的论文表明,非标准理想存在于$ l ^ 1(omega)$中。由Dales和McClure成功将Hisproof导出到连续案例$ L ^ 1(R ^ +,omega)$,但仍然困难。在本文中,我们首先提出一个小改进:$ l ^ 1(omega)$和$ L ^ 1(R ^ +,omega)$中非标准理想的存在的新的和容易的证明。新的证明基于我们引入的``非标准双对''的思想,然后我们可以进行更大的改进:我们在包含支持功能的$ L ^ 1(R ^ +,omega)$中定义非标准理想一直扩展到$ R ^ + $的零值,从而解决了该区域已成为一个臭名昭著的问题。

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