Zahra Alimohammadi, Ali Rejali
In This paper, we study the concept of weakly almost periodic functions on Frechet algebras. For a Frechet algebra A, we show that WAP(A)=wap(A). We also show that A** is Arens regular if and only if both A and WAP(A)* are Arens regular. Finally, for a sequence of Frechet algebras (An), we prove that the Frechet algebra \ell^1-\prod An is Arens regular if and only if each An is Arens regular.
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Radicals of Biduals of Beurling Algebras Can Be Different for the Two Arens Products
本文研究了Beurling代数双范数在两种Arens乘积下的Radicals差异，通过自由群的例子证明了两种乘积下Radicals可能不同。
Characterizations of Asplund and Tame Functionals using Arens Products
本文研究了Banach代数双极中Arens积与泛函结构正则性之间的关系，提出新的Asplund和Tame泛函特征化标准，并应用于局部紧群的群代数。
The order bidual of C(X) for a realcompact space
本文将紧空间 $\mathrm C(X)$ 双对偶的 Banach 代数等距同构结果推广至实紧空间，证明赋予 Arens 乘积的序双对偶作为 $f$-代数与某实紧空间的连续函数环同构且在同胚意义下唯一。
We prove that the bidual of a Beurling algebra on $\mathbb{Z}$, considered as a Banach algebra with the first Arens product, can never be semisimple. We then show that ${\rm rad\,}(\ell^{\, 1}(\oplus_{i=1}^\infty \mathbb{Z})")$ contains nilpotent elements of every index. Each of these results settles a question of Dales and Lau. Finally we show that there exists a weight $ω$ on $\mathbb{Z}$ such that the bidual of $\ell^{\, 1}(\mathbb{Z}, ω)$ contains a radical element which is not nilpotent.
Order continuity of Arens extensions of regular multilinear operators
本文研究了正则多重线性算子Arens延拓的序连续性，通过反例说明现有结果无法推广至整个双对偶乘积，并建立了使其在全双对偶乘积上序连续的条件，同时证明了延拓至少在单变量上序连续。
Annihilators in the bidual of generalized group algebra of a discrete group
本文研究离散群广义群代数二次对偶中关于两种 Arens 乘积的零化子，利用自然数集上的非主超滤子构造出一族不在拓扑中心中的显式零化子，并由此证明该广义群代数不是强 Arens 非正则的。
We prove that all Arens extensions of finite rank Riesz multimorphisms taking values in Archimedean Riesz spaces coincide and are Riesz multimorphisms. Partial results for arbitrary Riesz multimorphisms are obtained. We also prove that, for a class of Banach lattices $F$, which includes $F = c_0, \ell_p, c_0(\ell_p), \ell_p(c_0), \ell_p(\ell_s), 1 < p,s < \infty$, among many others, all Aron-Berner extensions of $F$-valued Riesz multimorphisms between Banach lattices are Riesz multimorphisms.
By extending the notion of Arens regularity of bilinear mappings, we say that a bounded trilinear map on Banach spaces id Aron--Berner regular when all its six Aron-Berner extensions to the bidual spaces coincide. We give some results on the Aron-Berner regularity of certain trilinear maps. We then focus on the bidual, $E^{**},$ of a Jordan banach triple system $(E,π)$, and investigate those conditions under which $E^{**}$ is itself a Jordan Banach triple system under each of the Aron-Berner extensions of the triple product $π.$ We also compare these six triple products with those arising from…
A note on the stability of Arens products under small perturbations of multiplication
本文研究Banach代数乘法小扰动对双对偶上Arens积的影响，证明Arens不规则性在足够小扰动下稳定，且等价于一致代数的Banach函数代数的Arens正则性在小扰动下保持稳定。
It is shown that every continuous homomorphism of Arens-Michael algebras can be obtained as the limit of a morphism of certain projective systems consisting of Fréchet algebras. Based on this we prove that a complemented subalgebra of an uncountable product of Fréchet algebras is topologically isomorphic to the product of Fréchet algebras. These results are used to characterize injective objects of the category of locally convex topological vector spaces. Dually, it is shown that a complemented subspace of an uncountable direct sum of Banach spaces is topologically isomorphic to the direct sum…
For a discrete group G with Fourier algebra A(G), we study the topological centre $Z_t$ of the bidual. If G is amenable, then $Z_t$ = A(G). But if G contains a non-abelian free group $F_r$, we show that $Z_t$ is strictly larger than A(G). Furthermore, it is shown that the subalgebra of radial functions in A(G) is Arens regular.
Let $\mathcal{A}$ be a $C^*$-algebra, and consider the Banach algebra $\mathcal{A} \otimes_γ\mathcal{A}$, where $\otimes_γ$ denotes the projective Banach space tensor product; if $\mathcal{A}$ is commutative, this is the Varopoulos algebra $V_\mathcal{A}$. It has been an open problem for more than 35 years to determine precisely when $\mathcal{A} \otimes_γ\mathcal{A}$ is Arens regular. Even the situation for commutative $\mathcal{A}$, in particular the case $\mathcal{A} = \ell_\infty$, has remained unsolved. We solve this classical question for arbitrary $C^*$-algebras by using von Neumann alg…
We construct the weak nonstandard hull of a normed linear space X from *X (the nonstandard extension of X) using the weak topology on X. The bidual (i.e. the second dual) X" is shown to be isometrically isomorphic to the weak nonstandard hull of X. Examples and applications to C*-algebras are given, including a simple proof of the Sherman-Takeda Theorem. As a consequence, the weak nonstandard hull of a C*-algebra is always a von Neumann algebra. Moreover a natural representation of the Arens product is given.
Orthogonally additive polynomials on the bidual of Banach algebras
本文研究Banach代数及其二次对偶的k正交加性性质，探讨k齐次多项式的延拓及两者性质的关联，并验证ℓ¹的二次对偶具有该性质。
The Arens products are the standard way of extending the product from a Banach algebra $\mc A$ to its bidual $\mc A''$. Ultrapowers provide another method which is more symmetric, but one that in general will only give a bilinear map, which may not be associative. We show that if $\mc A$ is Arens regular, then there is at least one way to use an ultrapower to recover the Arens product, a result previously known for C$^*$-algebras. Our main tool is a Principle of Local Reflexivity result for modules and algebras.
For an Arens-Michael algebra $A$ we consider a class of $A$-$\hat{\otimes}$-bimodules which are invertible with respect to the projective bimodule tensor product. We call such bimodules topologically invertible over $A$. Given a Fréchet-Arens-Michael algebra $A$ and an topologically invertible Fréchet $A$-$\hat{\otimes}$-bimodule $M$, we construct an Arens-Michael algebra $\widehat{L}_A(M)$ which serves as a topological version of the Laurent tensor algebra $L_A(M)$. Also, for a fixed algebra $B$ we provide a condition on an invertible $B$-bimodule $N$ sufficient for the Arens-Michael envelope…
We provide a survey of the similarities and differences between Banach and Frechet algebras including some known results and examples. We also collect some important generalizations in abstract harmonic analysis; for example, the generalization of the concepts of vector-valued Lipschitz algebras, abstract Segal algebras, Arens regularity, amenability, weak amenability, ideal amenability, etc.
We investigate the notion of Connes-amenability for dual Banach algebras, as introduced by Runde, for bidual algebras and weighted semigroup algebras. We provide some simplifications to the notion of a $σWC$-virtual diagonal, as introduced by Runde, especially in the case of the bidual of an Arens regular Banach algebra. We apply these results to discrete, weighted, weakly cancellative semigroup algebras, showing that these behave in the same way as C$^*$-algebras with regards Connes-amenability of the bidual algebra. We also show that for each one of these cancellative semigroup algebras $l^1…
Geometry of Banach algebra $\mA$ and the bidual of $L^1(G,\mA)$
本文研究广义群代数$L^1(G,\mA)$双对偶空间在Arens乘积下的拓扑中心与伪中心，将Lau-Losert经典结果推广到Banach代数值情形，并利用向量测度与Cohen分解定理给出相关刻画。
We prove that a countable semigroup $S$ is locally finite if and only if the Arens-Michael envelope of its semigroup algebra is a $(DF)$-space. This is a counterpart to a recent result of the author, which asserts that $S$ is finitely generated if and only if the Arens-Michael envelope is a Fréchet space.
Noncommutative complex analytic geometry of a contractive quantum plane
本文利用 Arens–Michael 包、Fréchet 代数预层与非交换 Harte 谱刻画 |q|≠1 时量子 q-平面的非交换复解析几何，并解决其函数演算与谱映射问题。
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