arXiv subjects

M. Amyari

Publications and source records attributed to M. Amyari.

4 recordsLinked to original sources

arXiv2018

Parallelism in Hilbert $K(\mathcal{H})$-modules

Let $(\mathcal{H}, [\cdot, \cdot ])$ be a Hilbert space and $K(\mathcal{H})$ be the $C^*$-algebra of compact operators on $\mathcal{H}$. In this paper, we present some characterizations of the norm-parallelism for elements of a Hilbert $K(\mathcal{H})$-module $\mathcal{E}$ by employing the minimal projections on $\mathcal{H}$. Let $T,S\in \mathcal{L(\mathcal{E})}$. We show that $T \| S$ if and only if there exists a sequence of basic vectors $\{x_n\}^{ξ_n}$ in $\mathcal{E}$ such that $\lim_n [\langle Tx_n, Sx_n \rangle ξ_n, ξ_n ] = λ\| T\| \| S\|$ for some $λ\in \mathbb{T}$. In addition, we give some equivalence assertions about the norm-parallelism of "compact" operators on a Hilbert $C^*$-module.

math.FA↗

arXiv2018

The operator--valued parallelism and norm-parallelism in matrices

Let $\mathcal{H}$ be a Hilbert space, and let $K(\mathcal{H})$ be the $C^*$-algebra of compact operators on $\mathcal{H}$. In this paper, we present some characterizations of the norm-parallelism for elements of a Hilbert $K(\mathcal{H})$-module by employing the Birkhoff--James orthogonality. Among other things, we present a characterization of transitive relation of the norm-parallelism for elements in a certain Hilbert $K(\mathcal{H})$-module. We also give some characterizations of the Schatten $p$-norms and the operator norm-parallelism for matrices.

math.FA↗

arXiv2012

Quasi-representations of Finsler modules over C*-algebras

We show that every Finsler module over a $C^*$-algebra has a quasi-representation into the Banach space $\mathbb{B}(\mathscr{H},\mathscr{K})$ of all bounded linear operators between some Hilbert spaces $\mathscr{H}$ and $\mathscr{K}$. We define the notion of completely positive $φ$-morphism and establish a Stinespring type theorem in the framework of Finsler modules over $C^*$-algebras. We also investigate the nondegeneracy and the irreducibility of quasi-representations.

math.OA↗

arXiv2005

Approximate Homomorphisms of Ternary Semigroups

A mapping $f:(G_1,[ ]_1)\to (G_2,[ ]_2)$ between ternary semigroups will be called a ternary homomorphism if $f([xyz]_1)=[f(x)f(y)f(z)]_2$. In this paper, we prove the generalized Hyers--Ulam--Rassias stability of mappings of commutative semigroups into Banach spaces. In addition, we establish the superstability of ternary homomorphisms into Banach algebras endowed with multiplicative norms.

math-ph↗