No Arabic abstract
For a finite, strongly connected $k$-graph $Lambda$, an Huef, Laca, Raeburn and Sims studied the KMS states associated to the preferred dynamics of the $k$-graph $C^*$-algebra $C^*(Lambda)$. They found that these KMS states are determined by the periodicity of $Lambda$ and a certain Borel probability measure $M$ on the infinite path space $Lambda^infty$ of $Lambda$. Here we consider different dynamics on $C^*(Lambda)$, which arise from a functor $y: Lambda to mathbb{R}_+$ and were first proposed by McNamara in his thesis. We show that the KMS states associated to McNamaras dynamics are again parametrized by the periodicity group of $Lambda$ and a family of Borel probability measures on the infinite path space. Indeed, these measures also arise as Hausdorff measures on $Lambda^infty$, and the associated Hausdorff dimension is intimately linked to the inverse temperatures at which KMS states exist. Our construction of the metrics underlying the Hausdorff structure uses the functors $y: Lambda to mathbb{R}_+$; the stationary $k$-Bratteli diagram associated to $Lambda$; and the concept of exponentially self-similar weights on Bratteli diagrams.
Given a self-similar $K$ set defined from an iterated function system $Gamma=(gamma_1,ldots,gamma_n)$ and a set of function $H={h_i:Ktomathbb{R}}_{i=1}^d$ satisfying suitable conditions, we define a generalized gauge action on Kawjiwara-Watatani algebras $mathcal{O}_Gamma$ and their Toeplitz extensions $mathcal{T}_Gamma$. We then characterize the KMS states for this action. For each $betain(0,infty)$, there is a Ruelle operator $mathcal{L}_{H,beta}$ and the existence of KMS states at inverse temperature $beta$ is related to this operator. The critical inverse temperature $beta_c$ is such that $mathcal{L}_{H,beta_c}$ has spectral radius 1. If $beta<beta_c$, there are no KMS states on $mathcal{O}_Gamma$ and $mathcal{T}_Gamma$; if $beta=beta_c$, there is a unique KMS state on $mathcal{O}_Gamma$ and $mathcal{T}_Gamma$ which is given by the eigenmeasure of $mathcal{L}_{H,beta_c}$; and if $beta>beta_c$, including $beta=infty$, the extreme points of the set of KMS states on $mathcal{T}_Gamma$ are parametrized by the elements of $K$ and on $mathcal{O}_Gamma$ by the set of branched points.
Given a positive function on the set of edges of an arbitrary directed graph $E=(E^0,E^1)$, we define a one-parameter group of automorphisms on the C*-algebra of the graph $C^*(E)$, and study the problem of finding KMS states for this action. We prove that there are bijective correspondences between KMS states on $C^*(E)$, a certain class of states on its core, and a certain class of tracial states on $C_0(E^0)$. We also find the ground states for this action and give some examples.
We develop methods for computing graded K-theory of C*-algebras as defined in terms of Kasparov theory. We establish grad
We initiate the study of real $C^*$-algebras associated to higher-rank graphs $Lambda$, with a focus on their $K$-theory. Following Kasparov and Evans, we identify a spectral sequence which computes the $mathcal{CR}$ $K$-theory of $C^*_{mathbb R} (Lambda, gamma)$ for any involution $gamma$ on $Lambda$, and show that the $E^2$ page of this spectral sequence can be straightforwardly computed from the combinatorial data of the $k$-graph $Lambda$ and the involution $gamma$. We provide a complete description of $K^{CR}(C^*_{mathbb R}(Lambda, gamma))$ for several examples of higher-rank graphs $Lambda$ with involution.
We establish exact sequences in $KK$-theory for graded relative Cuntz-Pimsner algebras associated to nondegenerate $C^*$-correspondences. We use this to calculate the graded $K$-theory and $K$-homology of relative Cuntz-Krieger algebras of directed graphs for gradings induced by ${0,1}$-valued labellings of their edge sets.