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Jorge Plazas

Publications and source records attributed to Jorge Plazas.

6 recordsLinked to original sources
arXiv2021

Hecke operators in Bredon (co)homology, K-(co)homology and Bianchi groups

In this article we provide a framework for the study of Hecke operators acting on the Bredon (co)homology of an arithmetic discrete group. Our main interest lies in the study of Hecke operators for Bianchi groups. Using the Baum-Connes conjecture, we can transfer computations in Bredon homology to obtain a Hecke action on the $K$-theory of the reduced $C^{*}$-algebra of the group. We show the power of this method giving explicit computations for the group $SL_2(\mathbb{Z}[i])$. In order to carry out these computations we use an Atiyah-Segal type spectral sequence together with the Bredon homology of the classifying space for proper actions.

math.KT↗
arXiv2013

Noncommutative geometry of groups like $Γ_0(N)$

We show that the Connes-Marcolli $GL_{2}$-system can be represented on the Big Picture, a combinatorial gadget introduced by Conway in order to understand various results about congruence subgroups pictorially. In this representation the time evolution of the system is implemented by Conway's distance between projective classes of commensurable lattices. We exploit these results in order to associate quantum statistical mechanical systems to congruence subgroups in a way appropriate for the study of monstrous moonshine.

math-ph↗
arXiv2007

Examples of noncommutative manifolds: complex tori and spherical manifolds

We survey some aspects of the theory of noncommutative manifolds focusing on the noncommutative analogs of two-dimensional tori and low-dimensional spheres. We are particularly interested in those aspects of the theory that link the differential geometry and the algebraic geometry of these spaces.

math.QA↗
arXiv2007

Quantum statistical mechanics and class field Theory

We survey some results relating noncommutative geometry to the class field theory of number fields. These results appear within the context of quantum statistical mechanics where some arithmetic properties of a given number field can be realized in terms of the structure of equilibrium states of a quantum statistical mechanical system.

math.NT↗
arXiv2007

Arithmetic structures on noncommutative tori with real multiplication

We study the homogeneous coordinate rings of real multiplication noncommutative tori as defined by A. Polishchuk. Our aim is to understand how these rings give rise to an arithmetic structure on the noncommutative torus. We start by giving an explicit presentation of these rings in terms of their natural generators. This presentation gives us information about the rationality of the rings and is the starting point for the analysis of the corresponding geometric data. Linear bases for these rings are also discussed. The basic role played by theta functions in these computations gives relations with elliptic curves at the level of modular curves. We use the modularity of these coordinate rings to obtain algebras which do no depend on the choice of a complex structure on the noncommutative torus. These algebras are obtained by an averaging process over (limiting) modular symbols.

math.QA↗