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Graph Theory versus Minimum Rank for Index Coding [PDF]

open access: green2014 IEEE International Symposium on Information Theory, 2014
We obtain novel index coding schemes and show that they provably outperform all previously known graph theoretic bounds proposed so far. Further, we establish a rather strong negative result: all known graph theoretic bounds are within a logarithmic ...
Dimakis, Alexandros G.   +2 more
core   +9 more sources

On the K-theory of twisted higher-rank-graph C*-algebras [PDF]

open access: greenJournal of Mathematical Analysis and Applications, 2012
We investigate the K-theory of twisted higher-rank-graph algebras by adapting parts of Elliott's computation of the K-theory of the rotation algebras.
Aidan Sims   +24 more
core   +13 more sources

C*-algebras of higher-rank graphs from groups acting on buildings, and explicit computation of their K-theory [PDF]

open access: greenPublicacions Matemàtiques, 2021
We unite elements of category theory, K-theory, and geometric group theory, by defining a class of groups called $k$-cube groups, which act freely and transitively on the product of $k$ trees, for arbitrary $k$. The quotient of this action on the product
Mutter, Sam A.   +2 more
core   +9 more sources

A dual graph construction for higher-rank graphs, and $K$-theory for finite 2-graphs [PDF]

open access: greenProceedings of the American Mathematical Society, 2004
Given a $k$-graph $\Lambda$ and an element $p$ of $\NN^k$, we define the dual $k$-graph, $p\Lambda$. We show that when $\Lambda$ is row-finite and has no sources, the $C^*$-algebras $C^*(\Lambda)$ and $C^*(p\Lambda)$ coincide.
Allen, Stephen, Pask, David, Sims, Aidan
core   +10 more sources

Real and complex K-theory for higher rank graph algebras arising from cube complexes [PDF]

open access: greenAnnals of K-theory
Using the Evans spectral sequence and its counter-part for real $K$-theory, we compute both the real and complex $K$-theory of several infinite families of $C^*$-algebras based on higher-rank graphs of rank $3$ and $4$. The higher-rank graphs we consider arise from double-covers of cube complexes. By considering the real and complex $K$-theory together,
Jeffrey L. Boersema, Alina Vdovina
semanticscholar   +5 more sources

THE K-THEORY OF THE -ALGEBRAS OF 2-RANK GRAPHS ASSOCIATED TO COMPLETE BIPARTITE GRAPHS [PDF]

open access: hybridJournal of the Australian Mathematical Society, 2021
AbstractUsing a result of Vdovina, we may associate to each complete connected bipartite graph$\kappa $a two-dimensional square complex, which we call a tile complex, whose link at each vertex is$\kappa $. We regard the tile complex in two different ways, each having a different structure as a$2$-rank graph.
Sam A. Mutter
openalex   +5 more sources

Structure theory and stable rank for C*-algebras of finite higher-rank graphs [PDF]

open access: greenProceedings of the Edinburgh Mathematical Society, 2021
AbstractWe study the structure and compute the stable rank of$C^{*}$-algebras of finite higher-rank graphs. We completely determine the stable rank of the$C^{*}$-algebra when the$k$-graph either contains no cycle with an entrance or is cofinal. We also determine exactly which finite, locally convex$k$-graphs yield unital stably finite$C^{*}$-algebras ...
David Pask, Adam Sierakowski, Aidan Sims
openalex   +5 more sources

K-theory and homotopies of 2-cocycles on higher-rank graphs [PDF]

open access: bronzePacific Journal of Mathematics, 2015
This paper continues our investigation into the question of when a homotopy $ = \{ _t\}_{t \in [0,1]}$ of 2-cocycles on a locally compact Hausdorff groupoid $\mathcal{G}$ gives rise to an isomorphism of the $K$-theory groups of the twisted groupoid $C^*$-algebras: $K_*(C^*(\mathcal{G}, _0)) \cong K_*(C^*(\mathcal{G}, _1)).$ In particular, we ...
Elizabeth Gillaspy
openalex   +5 more sources

Hyperspectral Anomaly Detection via Graph Dictionary-Based Low Rank Decomposition with Texture Feature Extraction

open access: yesRemote Sensing, 2020
The accuracy of anomaly detection in hyperspectral images (HSIs) faces great challenges due to the high dimensionality, redundancy of data, and correlation of spectral bands.
Shangzhen Song   +3 more
doaj   +2 more sources

Rank-two 5d SCFTs from M-theory at isolated toric singularities: a systematic study [PDF]

open access: yesJournal of High Energy Physics, 2020
We carry out a detailed exploration of the deformations of rank-two five-dimensional superconformal field theories (SCFTs) T X $$ {\mathcal{T}}_{\mathbf{X}} $$ , which are geometrically engineered by M-theory on the space transverse to isolated toric ...
Vivek Saxena
doaj   +2 more sources

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