1. On extremal (almost) edge-girth-regular graphsGabriela Araujo-Pardo, György Kiss, István Porupsánszki, 2025, izvirni znanstveni članek Opis: A k-regular graph of girth g is called an edge-girth-regular graph, or an egr-graph for short, if each of its edges is contained in exactly λ distinct g-cycles. An egr-graph is called extremal for the triple (k, g, λ) if has the smallest possible order. We prove that some graphs arising from incidence graphs of finite planes are extremal egr-graphs. We also prove new lower bounds on the order of egr-graphs.
Ključne besede: edge-girth-regular graph, cage problem, finite biaffine planes
Objavljeno v RUP: 03.11.2025; Ogledov: 133; Prenosov: 1
 Celotno besedilo (547,76 KB) |
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3. Primitive, edge-short, isometric, and pantochordal cyclesGover E. C. Guzman, Marcos E. González Laffitte, André Fujita, Peter F. Stadler, 2025, izvirni znanstveni članek Opis: A cycle in a graph G is said to be primitive from its vertex x if at least one of its edges does not belong to any shorter cycle that passes through x. This type of cycle and an associated notion of extended neighborhoods play a key role in message-passing algorithms that compute spectral properties of graphs with short loops. Here, we investigate such primitive cycles and graphs without long primitive cycles in a more traditional graph-theoretic framework. We show that a cycle is primitive from all its vertices if and only if it is isometric. We call a cycle fully redundant cycles if it is not primitive from any of its vertices and show that fully redundant cycles, in particular, are not edge short, i.e., they cannot be represented as the edge-disjoint union of a single edge and two shortest paths in G. The families Rk and Lk of graphs with all cycles of length at least k + 1 being fully redundant and not edge-short, respectively, coincide for k = 3 and k = 4. In these graphs, all cycles of length at least k + 1 are pantochordal, i.e., each of their vertices is incident with a chord. None of these results generalizes to k ≥ 5. Moreover, R₃ = L₃ turn out to be the block graphs, and R₄ = L₄ are the graphs with complete multi-partite blocks. The cographs, finally, are shown to form a proper subset of R₅.
Ključne besede: edge-short cycle, chord, block-graph, complete multipartite graph, wheel graphs, cographs, geodesic cycles, Hamiltonian cycles
Objavljeno v RUP: 03.11.2025; Ogledov: 90; Prenosov: 0
Celotno besedilo (478,50 KB) |
4. Basic tetravalent oriented graphs of independent-cycle typeNemanja Poznanović, Cheryl E. Praeger, 2025, izvirni znanstveni članek Opis: The family OG(4) consisting of graph-group pairs (Γ, G), where Γ is a finite, connected, 4-valent graph admitting a G-vertex-, and G-edge-transitive, but not G-arc-transitive action, has recently been examined using a normal quotient methodology. A subfamily of OG(4) has been identified as ‘basic’, due to the fact that all members of OG(4) are normal covers of at least one basic pair. We provide an explicit classification of those basic pairs (Γ, G) which have at least two independent cyclic G-normal quotients (these are G-normal quotients which are not extendable to a common cyclic normal quotient).
Ključne besede: half-arc-transitive, vertex-transitive graph, edge-transitive graph, normal cover, cycle graph
Objavljeno v RUP: 21.10.2025; Ogledov: 170; Prenosov: 1
Celotno besedilo (398,19 KB) |
5. Some recent discoveries about half-arc-transitive graphs : dedicated to Dragan Marušič on the occasion of his 60th birthdayMarston D. E. Conder, Primož Potočnik, Primož Šparl, 2015, izvirni znanstveni članek Opis: We present some new discoveries about graphs that are half-arc-transitive (that is, vertex- and edge-transitive but not arc-transitive). These include the recent discovery of the smallest half-arc-transitive 4-valent graph with vertex-stabiliser of order 4, and the smallest with vertex-stabiliser of order 8, two new half-arc-transitive 4-valent graphs with dihedral vertex-stabiliser ▫$D_4$▫ (of order 8), and the first known half-arc-transitive 4-valent graph with vertex-stabiliser of order 16 that is neither abelian nor dihedral. We also use half-arc-transitive group actions to provide an answer to a recent question of Delorme about 2-arc-transitive digraphs that are not isomorphic to their reverse.
Ključne besede: graph, edge-transitive, vertex-transitive, arc-transitive, half arc-transitive
Objavljeno v RUP: 31.12.2021; Ogledov: 2260; Prenosov: 22
Celotno besedilo (333,06 KB) |
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7. Edge elimination and weighted graph classesJesse Beisegel, Nina Chiarelli, Ekkehard Köhler, Matjaž Krnc, Martin Milanič, Nevena Pivač, Robert Scheffler, Martin Strehler, 2020, objavljeni znanstveni prispevek na konferenci Ključne besede: edge elimination, weighted graph, split graph, threshold graph, chain graph, linear-time recognition algorithm
Objavljeno v RUP: 10.11.2020; Ogledov: 2860; Prenosov: 36
 Povezava na celotno besedilo |
8. Edge elimination schemes of weighted graph classes, Workshop on Graph Modification algorithms, experiments and new problems, 23rd - 24th January 2020, Bergen, NorwayMartin Milanič, Jesse Beisegel, Nina Chiarelli, Ekkehard Köhler, Matjaž Krnc, Nevena Pivač, Robert Scheffler, Martin Strehler, 2020, vabljeno predavanje na konferenci brez natisa Ključne besede: graph class, edge elimination scheme, sandwich monotonicity
Objavljeno v RUP: 28.05.2020; Ogledov: 2840; Prenosov: 0 |
9. Avoidable vertices and edges in graphsJesse Beisegel, Maria Chudnovsky, Vladimir Gurvich, Martin Milanič, Mary Agnes Milanič, 2019, objavljeni znanstveni prispevek na konferenci Ključne besede: simplicial vertex, avoidable vertex, avoidable edge, avoidable path, maximum weight clique problem, polynomial-time algorithm, hole-cyclically orientable graph
Objavljeno v RUP: 20.08.2019; Ogledov: 3460; Prenosov: 161
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