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math.CO2026

Cheeger-type inequalities for the second largest spectral gap from of the normalized Laplacian

Lies Beers, Raffaella Mulas, Jan Petr

We study the second largest spectral gap from of the normalized Laplacian of a graph, a quantity that appears in the literature in connection with random walks, expander graphs…

math.CO2026

Spectral Perspectives on FAT Graph Colorings

Lies Beers, Raffaella Mulas

We investigate Fair and Tolerant (FAT) graph colorings, a coloring framework in which each vertex is allowed to share its color with a prescribed fraction of its neighbors, while t…

math.CO2026

Coloring outside the lines: Spectral bounds for generalized hypergraph colorings

Lies Beers, Raffaella Mulas

It is known that, for an oriented hypergraph with (vertex) coloring number and smallest and largest normalized Laplacian eigenvalues and , respectively, the inequ…

math.CO2026

Uniform density in matroids, matrices and graphs

Karel Devriendt, Raffaella Mulas

We give new characterizations for the class of uniformly dense matroids and study applications of these characterizations to graphic and real representable matroids. We show that a…

math.CO2025

Fair and Tolerant (FAT) Graph Colorings

Lies Beers, Raffaella Mulas

We introduce and study Fair and Tolerant colorings (FAT colorings), where each vertex tolerates a given fraction of same-colored neighbors while fairness is preserved across the ot…

math.CO2024

Maximal colourings for graphs

Raffaella Mulas

We consider two different notions of graph colouring, namely, the -periodic colouring for vertices that has been introduced in 1974 by Bondy and Simonovits, and the periodic col…