Amenability constants for semilattice algebras
Amenability constants for semilattice algebras
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半格代数的适用常数
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
N. Spronk
中科院分区：
文献类型：
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作者：
M. Ghandehari;Hamed Hatami;N. Spronk
对任一有限交换幂等半群S半格，我们证明了如何计算它的半群代数ℓ1(S)的顺应常数。这个顺从性常数总是4N+1的形式。然后，我们证明了这给出了在半格上分次的某些Banach代数的顺从性常数的下界。我们还给出了一个交换Clifford半群Gn的例子，它的半群代数ℓ1(Gn)具有形式为41+4(n−1)/n的顺从性常数，我们还证明了不存在其半群代数的顺从性常数在5到9之间的交换半群。
For any finite commutative idempotent semigroup S, a semilattice, we show how to compute the amenability constant of its semigroup algebra ℓ1(S). This amenability constant is always of the form 4n+1. We then show that these give lower bounds to amenability constants of certain Banach algebras graded over semilattices. We also give example of a commutative Clifford semigroups Gn whose semigroup algebras ℓ1(Gn) admit amenability constants of the form 41+4(n−1)/n. We also show there is no commutative semigroup whose semigroup algebra has an amenability constant between 5 and 9.