arXiv subjects
Publications and source records attributed to Armando Sánchez-Nungaray.
In the present work we study for a given Banach space the quotient of the family of equivalent norms modulus the collinearity relationship and prove that under a Banach-Mazur type metric this family is a complete metric space, and we also prove the completeness of the family of constructible norms for the Banach space of bounded Lipschitzian mappings between convex sets of a Banach space.
We consider symmetric separately radial (with corresponding group $S_n\rtimes \mathbb{T}^n$) and alternating separately radial (with corresponding group $A_n\rtimes \mathbb{T}^n$) symbols, as well as the associated Toeplitz operators on the weighted Bergman spaces on the unit ball on $\mathbb{C}^n$. Using a purely representation theoretic approach we obtain that the $C^*$-algebras generated by each family of such Toeplitz operators is commutative. Furthermore, we show that the symmetric separately radial Toeplitz operators are more general than radial Toeplitz operators, i.e., every radial Toeplitz operator is a symmetric separately radial.
Let $n,m\ge 1$ and $α>0$. We denote by $\mathcal{F}_{α,m}$ the $m$-analytic Bargmann--Segal--Fock space, i.e., the Hilbert space of all $m$-analytic functions defined on $\mathbb{C}^n$ and square integrables with respect to the Gaussian weight $\exp(-α|z|^2)$. We study the von Neumann algebra $\mathcal{A}$ of bounded linear operators acting in $\mathcal{F}_{α,m}$ and commuting with all ``horizontal'' Weyl translations, i.e., Weyl unitary operators associated to the elements of $\mathbb{R}^n$. The reproducing kernel of $\mathcal{F}_{1,m}$ was computed by Youssfi [Polyanalytic reproducing kernels in $\mathbb{C}^n$, Complex Anal. Synerg., 2021, 7, 28]. Multiplying the elements of $\mathcal{F}_{α,m}$ by an appropriate weight, we transform this space into another reproducing kernel Hilbert space whose kernel $K$ is invariant under horizontal translations. Using the well-known Fourier connection between Laguerre and Hermite functions, we compute the Fourier transform of $K$ in the ``horizontal direction'' and decompose it into the sum of $d$ products of Hermite functions, with $d=\binom{n+m-1}{n}$. Finally, applying the scheme proposed by Herrera-Yañez, Maximenko, Ramos-Vazquez [Translation-invariant operators in reproducing kernel Hilbert spaces, Integr. Equ. Oper. Theory, 2022, 94, 31], we show that $\mathcal{F}_{α,m}$ is isometrically isomorphic to the space of vector-functions $L^2(\mathbb{R}^n)^d$, and $\mathcal{A}$ is isometrically isomorphic to the algebra of matrix-functions $L^\infty(\mathbb{R}^n)^{d\times d}$.
The non--commuting graph $Γ(G)$ of a non--abelian group $G$ is defined as follows. The vertex set $V(Γ(G))$ of $Γ(G)$ is $G\setminus Z(G)$ where $Z(G)$ denotes the center of $G$ and two vertices $x$ and $y$ are adjacent if and only if $xy\neq yx$. For non--abelian finite groups $G$ and $H$ it is conjectured that if $Γ(G) \cong Γ(H)$, then $|G|=|H|$. We prove the conjecture.
Following previous works for the unit ball, we define quasi-radial pseudo-homogeneous symbols on the projective space and obtain the corresponding commutativity results for Toeplitz operators. A geometric interpretation of these symbols in terms of moment maps is developed. This leads us to the introduction of a new family of symbols, extended pseudo-homogeneous, that provide larger commutative Banach algebras generated by Toeplitz operators. This family of symbols provides new commutative Banach algebras generated by Toeplitz operators on the unit ball.