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Immersions of graphs to the projective plane are studied. A classification of immersions up to regular homotopy is given. A complete invariant of immersions up to regular homotopy is constructed. Equivalence classes are described.

Geometric Topology · Mathematics 2017-03-21 Maxim A. Ivashkovskii

We classify the gauge-invariant ideals in the C*-algebras of infinite directed graphs, and describe the quotients as graph algebras. We then use these results to identify the gauge-invariant primitive ideals in terms of the structural…

Operator Algebras · Mathematics 2007-05-23 Teresa Bates , Jeong Hee Hong , Iain Raeburn , Wojciech Szymanski

What is a vector field on a C*-algebra is defined. Its relation to semigroups of endomorphisms was researched. Some results given about those vector fields and semigroups. There are also various constructions of semigroups including one…

Mathematical Physics · Physics 2012-12-04 Innocenti Maresin

It is proved that classifiable simple separable nuclear purely infinite C*-algebras having finitely generated K-theory and torsion-free K_1 are semiprojective. This is accomplished by exhibiting these algebras as C*-algebras of infinite…

Operator Algebras · Mathematics 2007-05-23 Jack Spielberg

Here we give an overview on the connection between wavelet theory and representation theory for graph $C^{\ast}$-algebras, including the higher-rank graph $C^*$-algebras of A. Kumjian and D. Pask. Many authors have studied different aspects…

Operator Algebras · Mathematics 2016-01-05 Carla Farsi , Elizabeth Gillaspy , Sooran Kang , Judith Packer

To any directed graph we associate an algebra with edges of the graph as generators and with relations defined by all pairs of directed paths with the same origin and terminus. Such algebras are related to factorizations of polynomials over…

Quantum Algebra · Mathematics 2016-09-07 Israel Gelfand , Vladimir Retakh , Shirlei Serconek , Robert Lee Wilson

This paper considers *-graphs in which all vertices have degree 4 or 6, and studies the question of calculating the genus of orientable 2-surfaces into which such graphs may be embedded. A *-graph is a graph endowed with a formal adjacency…

Combinatorics · Mathematics 2012-12-27 Tyler Friesen , Vassily Manturov

A multi-relational graph maintains two or more relations over a vertex set. This article defines an algebra for traversing such graphs that is based on an $n$-ary relational algebra, a concatenative single-relational path algebra, and a…

Discrete Mathematics · Computer Science 2011-05-26 Marko A. Rodriguez , Peter Neubauer

We introduce a revised notion of gauge action in relation with Leavitt path algebras. This notion is based on group schemes and captures the full information of the grading on the algebra as it is the case of the gauge action of the graph…

We show that the graph construction used to prove that a gauge-invariant ideal of a graph C*-algebra is isomorphic to a graph C*-algebra, and also used to prove that a graded ideal of a Leavitt path algebra is isomorphic to a Leavitt path…

Operator Algebras · Mathematics 2013-04-16 Efren Ruiz , Mark Tomforde

In this paper, we give a class of reconstructible graphs.

Combinatorics · Mathematics 2007-05-23 Tetsuya Hosaka

We describe constructions of infinite graphs which are not representable as integral graphs in the plane, addressing a question of Erd\H{o}s. We also mention some related problems.

Combinatorics · Mathematics 2024-02-14 Jozsef Solymosi

We investigate C^*-algebras generated by scaling elements. We generalize the Wold decomposition and Coburn's theorem on isometries to scaling elements. We also completely determine when the C^*-algebra generated by a scaling element…

Operator Algebras · Mathematics 2007-05-23 Takeshi Katsura

In this dissertation, we explore the structure of inversion graphs of permutations--a class of graphs that naturally arises by representing each permutation as a graph, where vertices correspond to entries and edges encode inversions.…

Combinatorics · Mathematics 2025-06-30 Sean Mandrick

We introduce $C^*$-algebras associated with directed graphs, along with two generalizations of this concept, namely Exel-Pardo $C^*$-algebras associated with a self-similar action of a group on a directed graph, and the $C^*$-algebras…

Operator Algebras · Mathematics 2026-04-21 Pere Ara

We geometrically describe the relation induced on a set of graphs by isomorphism of their associated graph C*-algebras as the smallest equivalence relation generated by five types of moves. The graphs studied have finitely many vertices and…

Operator Algebras · Mathematics 2019-10-28 Sara E. Arklint , Søren Eilers , Efren Ruiz

It is known that given a directed graph E and a subset X of vertices, the sum of the projections associated to the vertices in X in the C*-algebra of E converges strictly in the multiplier algebra to a projection P. Here we give a…

Operator Algebras · Mathematics 2013-01-04 Tyrone Crisp

We prove simplicity and pure infiniteness results for a certain class of labelled graph $C^*$-algebras. We show, by example, that this class of unital labelled graph $C^*$-algebras is strictly larger than the class of unital graph…

Operator Algebras · Mathematics 2008-01-15 T. Bates , D. A. Pask

We define an operation of jets on graphs inspired by the corresponding notion in commutative algebra and algebraic geometry. We examine a few graph theoretic properties and invariants of this construction, including chromatic numbers,…

Combinatorics · Mathematics 2022-03-09 Federico Galetto , Elisabeth Helmick , Molly Walsh

We give a construction of Kirchberg algebras from graphs. By using product graphs in the construction we are able to provide models for general (UCT) Kirchberg algebras while maintaining the explicit generators and relations of the…

Operator Algebras · Mathematics 2007-05-23 Jack Spielberg