arXiv subjects

Francisco Torres-Ayala

Publications and source records attributed to Francisco Torres-Ayala.

5 recordsLinked to original sources

arXiv2025

About an isomorphism between the Beurling algebra with a weight dependent convolution and the $L^1(G)$ group algebra

We show that the Beurling algebra with a weight-dependent convolution and the group algebra $L^1(G)$ are isomorphic. In particular, using this isomorphism, we extend some results of the algebra $\mathscr{L}^1(G,ω)$ presented in recent articles. As a main result, we explicitly construct the equivalence between unitary representations of the group and non-degenerate $\ast$-representations of this algebra.

math.FA↗

arXiv2019

Conditionally Free Reduced Products of Hilbert Spaces

We present a product of pairs of pointed Hilbert spaces that, in the context of Bozėjko, Leinert and Speicher's theory of conditionally free probability, plays the role of the reduced free product of pointed Hilbert spaces, and thus gives a unified construction for the natural notions of independence defined by Muraki. We additionally provide important applications of this construction. We prove that, assuming minor restrictions, for any pair of conditionally free algebras there are copies of them that are conditionally free and also free, a property that is frequently assumed (as hypothesis) to prove several results in the literature. Finally, we give a short proof of the linearization property of the $^cR$-transform (the analog of Voiculescu's $R$-transform in the context of conditionally free probability).

math.OA↗

arXiv2014

Conditions for Primitivity of unital amalgamated full free products of finite dimensional C*-algebras

We consider amalgamated unital full free products of the form $A_1*_DA_2$, where $A_1, A_2$ and $D$ are finite dimensional C*-algebras and there are faithful traces on $A_1$ and $A_2$ whose restrictions to $D$ agree. We provide several conditions on the matrices of partial multiplicities of the inclusions $D\hookrightarrow A_1$ and $D\hookrightarrow A_2$ that guarantee that the C*-algebra $A_1*_DA_2$ is primitive. If the ranks of the matrices of partial multiplicities are one, we prove that the algebra $A_1*_DA_2$ is primitive if and only if it has a trivial center.

math.OA↗

arXiv2012

Primitivity of unital full free products of residually finite dimensional C*-algebras

A C*-algebra is called primitive if it admits a faithful and irreducible *-representation. We show that if A_1 and A_2 are separable, unital, residually finite dimensional C*-algebras that are not both two dimensional, then their unital C*-algebra full free product, A = A_1*A_2, is primitive. It follows that A is antiliminal and the set of pure states is w*-dense in the state space.

math.OA↗

arXiv2010

Sum--of--squares results for polynomials related to the Bessis--Moussa--Villani conjecture

We show that the polynomial S_{m,k}(A,B), that is the sum of all words in noncommuting variables A and B having length m and exactly k letters equal to B, is not equal to a sum of commutators and Hermitian squares in the algebra R where X^2=A and Y^2=B, for all even values of m and k with 6 <= k <= m-10, and also for (m,k)=(12,6). This leaves only the case (m,k)=(16,8) open. This topic is of interest in connection with the Lieb--Seiringer formulation of the Bessis--Moussa--Villani conjecture, which asks whether the trace of S_{m,k}(A,B)) is nonnegative for all positive semidefinite matrices A and B. These results eliminate the possibility of using "descent + sum-of-squares" to prove the BMV conjecture. We also show that S_{m,4}(A,B) is equal to a sum of commutators and Hermitian squares in R when m is even and not a multiple of 4, which implies that the trace of S_{m,4}(A,B) is nonnegative for all Hermitian matrices A and B, for these values of m.

math.RA↗