M. Tobolski

collaborators

4 papers

math.RA2019

Graph algebras

Piotr M. Hajac, Mariusz Tobolski

This introduction to graphs and graph algebras provides the optimal bound for the number of all paths of length $k$ in a graph with $N \geq k$ edges and no loops. Our proof relies o…

math.QA2019

Non-surjective pullbacks of graph C*-algebras from non-injective pushouts of graphs

Alexandru Chirvasitu, Piotr M. Hajac, Mariusz Tobolski

We find a substantial class of pairs of $*$ -homomorphisms between graph C*-algebras of the form $C^{*} (E) ↪ C^{*} (G) ↞ C^{*} (F)$ whose pullback C*-algebra is…

math.OA2018

Pullbacks of graph C*-algebras from admissible pushouts of graphs

Piotr M. Hajac, Sarah Reznikoff, Mariusz Tobolski

We define an admissible decomposition of a graph $E$ into subgraphs $F_{1}$ and $F_{2}$ , and consider the intersection graph $F_{1} \cap F_{2}$ as a subgraph of both $F_{1}$ and $F_{2}$ . We pro…

math.RA2018

A graded pullback structure of Leavitt path algebras of trimmable graphs

Piotr M. Hajac, Atabey Kaygun, Mariusz Tobolski

Motivated by recent results in graph C*-algebras concerning an equivariant pushout structure of the Vaksman-Soibelman quantum odd spheres, we introduce a class of graphs called tri…