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math.CO2026

A Note on Grünbaum's Conjecture about Longest Cycles and Paths

Masaki Kashima, Kenta Ozeki, Leilei Zhang

Let denote the circumference of a graph , i.e., the number of vertices in its longest cycle. For positive integers and with , let be the cla…

math.CO2025

Spanning path-cycle systems with given end-vertices in regular graphs (full version)

Yoshimi Egawa, Mikio Kano, Kenta Ozeki

We prove the following theorem. Let be an integer, and be a -free -edge-connected -regular graph. Then, for every set of even number of vertices of…

math.CO2025

A generalization of an ear decomposition and k-trees in highly connected star-free graphs

Shun-ichi Maezawa, Kenta Ozeki, Masaki Yamamoto +1

In this paper, we introduce a generalized version of an ear decomposition, called a -spider decomposition, for -connected star-free graphs with . Its application en…

math.CO2025

Odd coloring of -trees

Masaki Kashima, Kenta Ozeki

An odd coloring of a graph is a proper coloring such that every non-isolated vertex has a color that appears at an odd number of its neighbors. This notion was introduced by Petrše…

math.CO2024

On odd covers of cliques and disjoint unions

Calum Buchanan, Alexander Clifton, Eric Culver +5

Babai and Frankl posed the ``odd cover problem" of finding the minimum cardinality of a collection of complete bipartite graphs such that every edge of the complete graph of order…

math.CO2024

Reconfiguration of Independent Transversals

Pjotr Buys, Ross J. Kang, Kenta Ozeki

Given integers and , suppose there is a graph of maximum degree and a partition of its vertices into blocks of size at least . By a seminal result of Haxel…