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Michael Hartglass

Publications and source records attributed to Michael Hartglass.

14 recordsLinked to original sources
arXiv2024

Uniqueness of extremal almost periodic states on the injective type III$_{1}$ factor

Let $R_\infty$ denote the Araki--Woods factor -- the unique separable injective type III$_{1}$ factor. For extremal almost periodic states $φ, ψ\in (R_\infty)_*$, we show that if $Δ_φ$ and $Δ_ψ$ have the same point spectrum then $ψ= φ\circ α$ for some $α\in $ Aut$(R_\infty)$. Consequently, the extremal almost periodic states on $R_\infty$ are parameterized by countable dense subgroups of $\mathbb{R}_+$, up to precomposition by automorphisms. As an application, we show that KMS states for generalized gauge actions on Cuntz algebras agree (up to an automorphism) with tensor products of Powers states on their von Neumann completions.

math.OA↗
arXiv2023

A Fair Shake: How close can the sum of $n$-sided dice be to a uniform distribution?

Two possibly unfair $n$-sided dice, both labelled $1, 2, \ldots, n$, are rolled, and the sum is recorded. How should the dice's sides be weighted so that the resulting sum is closest to the uniform distribution on $2, 3, \ldots, 2n$? We answer this question by explicitly identifying the optimal pair of dice. This resolves a question raised by Gasarch and Kruskal in 1999 in a surprising way. We present additional results for the case of more than two possibly unfair $n$-sided dice and for the hypothetical case where the weights on each die are permitted to be negative, but must still sum to one.

math.HO↗
arXiv2021

Compact Quantum Metric Spaces from Free Graph Algebras

Starting with a vertex-weighted pointed graph $(Γ,μ,v_0)$, we form the free loop algebra $\mathcal{S}_0$ defined in Hartglass-Penneys' article on canonical $\rm C^*$-algebras associated to a planar algebra. Under mild conditions, $\mathcal{S}_0$ is a non-nuclear simple $\rm C^*$-algebra with unique tracial state. There is a canonical polynomial subalgebra $A\subset \mathcal{S}_0$ together with a Dirac number operator $N$ such that $(A, L^2A,N)$ is a spectral triple. We prove the Haagerup-type bound of Ozawa-Rieffel to verify $(\mathcal{S}_0, A, N)$ yields a compact quantum metric space in the sense of Rieffel. We give a weighted analog of Benjamini-Schramm convergence for vertex-weighted pointed graphs. As our $\rm C^*$-algebras are non-nuclear, we adjust the Lip-norm coming from $N$ to utilize the finite dimensional filtration of $A$. We then prove that convergence of vertex-weighted pointed graphs leads to quantum Gromov-Hausdorff convergence of the associated adjusted compact quantum metric spaces. As an application, we apply our construction to the Guionnet-Jones-Shyakhtenko (GJS) $\rm C^*$-algebra associated to a planar algebra. We conclude that the compact quantum metric spaces coming from the GJS $\rm C^*$-algebras of many infinite families of planar algebras converge in quantum Gromov-Hausdorff distance.

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arXiv2021

Free products of finite-dimensional and other von Neumann algebras in terms of free Araki-Woods factors

We show that any free product of finite-dimensional von Neumann algebras equipped with non-tracial states is isomorphic to a free Araki-Woods factor with its free quasi-free state possibly direct sum a finite-dimensional von Neumann algebra. This gives a complete answer to questions posed by Dykema and Shlyakhtenko, which had been partially answered by work of Houdayer and work of Ueda. We also extend this to suitable infinite-dimensional von Neumann algebras with almost periodic states.

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arXiv2020

Realizations of Rigid C*-Tensor Categories as Bimodules over GJS C*-Algebras

Given an arbitrary countably generated rigid C*-tensor category, we construct a fully-faithful bi-involutive strong monoidal functor onto a subcategory of finitely generated projective bimodules over a simple, exact, separable, unital C*-algebra with unique trace. The C*-algebras involved are built from the category using the GJS-construction introduced in arXiv:0911.4728 and further studied in arXiv:1208.5505 and arXiv:1401.2486. Out of this category of Hilbert C*-bimodules, we construct a fully-faithful bi-involutive strong monoidal functor into the category of bi-finite spherical bimodules over an interpolated free group factor. The composite of these two functors recovers the functor constructed in arXiv:1208.5505

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arXiv2018

Non-tracial free graph von Neumann algebras

Given a finite, directed, connected graph $Γ$ equipped with a weighting $μ$ on its edges, we provide a construction of a von Neumann algebra equipped with a faithful, normal, positive linear functional $(\mathcal{M}(Γ,μ),φ)$. When the weighting $μ$ is instead on the vertices of $Γ$, the first author showed the isomorphism class of $(\mathcal{M}(Γ,μ),φ)$ depends only on the data $(Γ,μ)$ and is an interpolated free group factor equipped with a scaling of its unique trace (possibly direct sum copies of $\mathbb{C}$). Moreover, the free dimension of the interpolated free group factor is easily computed from $μ$. In this paper, we show for a weighting $μ$ on the edges of $Γ$ that the isomorphism class of $(\mathcal{M}(Γ,μ),φ)$ depends only on the data $(Γ,μ)$, and is either as in the vertex weighting case or is a free Araki-Woods factor equipped with a scaling of its free quasi-free state (possibly direct sum copies of $\mathbb{C}$). The latter occurs when the subgroup of $\mathbb{R}^+$ generated by $μ(e_1)\cdots μ(e_n)$ for loops $e_1\cdots e_n$ in $Γ$ is non-trivial, and in this case the point spectrum of the free quasi-free state will be precisely this subgroup. As an application, we give the isomorphism type of some infinite index subfactors considered previously by Jones and Penneys.

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arXiv2017

Free transport for interpolated free group factors

In this article, we study a form of free transport for the interpolated free group factors, extending the work of Guionnet and Shlyakhtenko for the usual free group factors. Our model for the interpolated free group factors comes from a canonical finite von Neumann algebra $\mathcal{M}(Γ, μ)$ associated to a finite, connected, weighted graph $(Γ,V,E, μ)$. With this model, we use an operator-valued version of Voiculescu's free difference quotient to state a Schwinger-Dyson equation which is valid for the generators of $\mathcal{M}(Γ, μ)$. We construct free transport for appropriate perturbations of this equation. Also, $\mathcal{M}(Γ, μ)$ can be constructed using the machinery of Shlyakhtenko's operator-valued semicircular systems

math.OA↗
arXiv2015

Free product C$^{*}$-algebras associated to graphs, free differentials, and laws of loops

We study a canonical C$^*$-algebra, $\mathcal{S}(Γ, μ)$, that arises from a weighted graph $(Γ, μ)$, specific cases of which were previously studied in the context of planar algebras. We discuss necessary and sufficient conditions of the weighting which ensure simplicity and uniqueness of trace of $\mathcal{S}(Γ, μ)$, and study the structure of its positive cone. We then study the $*$-algebra, $\mathcal{A}$, generated by the generators of $\mathcal{S}(Γ, μ)$, and use a free differential calculus and techniques of Charlesworth and Shlyakhtenko, as well as Mai, Speicher, and Weber to show that certain "loop" elements have no atoms in their spectral measure. After modifying techniques of Shlyakhtenko and Skoufranis to show that self adjoint elements $x \in M_{n}(\mathcal{A})$ have algebraic Cauchy transform, we explore some applications to eigenvalues of polynomials in Wishart matrices and to diagrammatic elements in von Neumann algebras initially considered by Guionnet, Jones, and Shlyakhtenko.

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arXiv2014

$C^*$-algebras from planar algebras I: canonical $C^*$-algebras associated to a planar algebra

From a planar algebra, we give a functorial construction to produce numerous associated $C^*$-algebras. Our main construction is a Hilbert $C^*$-bimodule with a canonical real subspace which produces Pimsner-Toeplitz, Cuntz-Pimsner, and generalized free semicircular $C^*$-algebras. By compressing this system, we obtain various canonical $C^*$-algebras, including Doplicher-Roberts algebras, Guionnet-Jones-Shlyakhtenko algebras, universal (Toeplitz-)Cuntz-Krieger algebras, and the newly introduced free graph algebras. This is the first article in a series studying canonical $C^*$-algebras associated to a planar algebra.

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arXiv2014

$C^*$-algebras from planar algebras II: the Guionnet-Jones-Shlyakhtenko $C^*$-algebras

We study the $C^*$-algebras arising in the construction of Guionnet-Jones-Shlyakhtenko (GJS) for a planar algebra. In particular, we show they are pairwise strongly Morita equivalent, we compute their $K$-groups, and we prove many properties, such as simplicity, unique trace, and stable rank 1. Interestingly, we see a $K$-theoretic obstruction to the GJS $C^*$-algebra analog of Goldman-type theorems for II$_1$-subfactors. This is the second article in a series studying canonical $C^*$-algebras associated to a planar algebra.

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arXiv2013

Rigid C^*-tensor categories of bimodules over interpolated free group factors

Given a countably generated rigid C^*-tensor category C, we construct a planar algebra P whose category of projections Pro is equivalent to C. From P, we use methods of Guionnet-Jones-Shlyakhtenko-Walker to construct a rigid C^*-tensor category Bim whose objects are bifinite bimodules over an interpolated free group factor, and we show Bim is equivalent to Pro. We use these constructions to show C is equivalent to a category of bifinite bimodules over L(F_infty).

math.OA↗
arXiv2006

On The Dimension of The Virtually Cyclic Classifying Space of a Crystallographic Group

In this paper we construct a model for the classifying space, BVCG, of a crystallographic group G of rank n relative to the family VC of virtually-cyclic subgroups of G. The model is used to show that there exists no other model for the virtually-cyclic classifying space of G with dimension less than vcd(G)+1, where vcd(G) denotes the virtual cohomological dimension of G. In addition, the dimension of our construction realizes this limit.

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