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Amenability of semigroups and common multiples in $ell^1_+$

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 نشر من قبل Tobias Fritz
 تاريخ النشر 2021
  مجال البحث
والبحث باللغة English
 تأليف Tobias Fritz




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In this note, we prove that a semigroup $S$ is left amenable if and only if every two nonzero elements of $ell^1_+(S)$ have a common nonzero right multiple, where $ell^1_+(S)$ is the positive part of the Banach algebra $ell^1(S)$, or equivalently the semiring of finite measures on $S$. This characterization of amenability is new even for groups.



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