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An $(a,b)$-biregular bipartite graph is a bipartite graph with bipartition $(X, Y)$ such that each vertex in $X$ has degree $a$ and each vertex in $Y$ has degree $b$. By the bipartite expander mixing lemma, biregular bipartite graphs have…

Combinatorics · Mathematics 2024-04-11 Dandan Fan , Xiaofeng Gu , Huiqiu Lin

We give an efficient algorithm that, given a graph $G$ and a partition $V_1,\ldots,V_m$ of its vertex set, finds either an independent transversal (an independent set $\{v_1,\ldots,v_m\}$ in $G$ such that $v_i\in V_i$ for each $i$), or a…

Combinatorics · Mathematics 2020-09-16 Alessandra Graf , Penny Haxell

In this paper, we explore completely regular codes in the Hamming graphs and related graphs. Experimental evidence suggests that many completely regular codes have the property that the eigenvalues of the code are in arithmetic progression.…

Combinatorics · Mathematics 2021-11-02 J. H. Koolen , W. S. Lee , W. J. Martin , H. Tanaka

Intuitively speaking, a bipartite graph is mirror if it can be drawn in the Cartesian plane in such a way that, the vertices of one stable are points in x=0, the vertices of the other stable set are points in x=1, the edges are straight…

Combinatorics · Mathematics 2013-12-13 Susana-Clara López , Francesc-Antoni Muntaner-Batle

Many authors have studied the dynamics of hyperbolic transcendental entire functions; these are those for which the postsingular set is a compact subset of the Fatou set. Equivalenty, they are characterized as being expanding.…

Dynamical Systems · Mathematics 2021-07-01 Leticia Pardo-Simón

An independent set may not contain both a vertex and one of its neighbours. This basic fact makes the uniform distribution over independent sets rather special. We consider the hard-core model, an essential generalization of the uniform…

Combinatorics · Mathematics 2025-09-04 Ewan Davies , Ross J. Kang

We study the zero sets of the independence polynomial on recursive sequences of graphs. We prove that for a maximally independent starting graph and a stable and expanding recursion algorithm, the zeros of the independence polynomial are…

Dynamical Systems · Mathematics 2024-11-25 Mikhail Hlushchanka , Han Peters

This paper studies bounds in a strong form of regularity for $3$-uniform hypergraphs which was developed by Frankl, Gowers, Kohayakawa, Nagle, R\"{o}dl, Skokan, and Schacht. Regular decompositions of this type involve two structural…

Combinatorics · Mathematics 2025-08-05 C. Terry

This paper is interested in independent sets (or equivalently, cliques) in uniform random cographs. We also study their permutation analogs, namely, increasing subsequences in uniform random separable permutations. First, we prove that,…

We study the asymptotics of large simple graphs constrained by the limiting density of edges and the limiting subgraph density of an arbitrary fixed graph $H$. We prove that, for all but finitely many values of the edge density, if the…

Combinatorics · Mathematics 2017-03-16 Richard Kenyon , Charles Radin , Kui Ren , Lorenzo Sadun

There has been a great deal of attention recently to graphs whose vertex set is a group, defined using the group structure. (The commuting graph, where two elements are joined if they commute, is the oldest and most famous example.) The…

Combinatorics · Mathematics 2026-02-03 Peter J. Cameron

Independent sets in graphs are sets of vertices containing no neighbors, and they represent a canonical spin system with hardcore constraints. Of particular interest is the setting of the boolean hypercube, where counting independent sets…

Probability · Mathematics 2025-11-11 Mriganka Basu Roy Chowdhury , Shirshendu Ganguly , Vilas Winstein

We prove tight upper bounds on the logarithmic derivative of the independence and matching polynomials of d-regular graphs. For independent sets, this theorem is a strengthening of the results of Kahn, Galvin and Tetali, and Zhao showing…

Combinatorics · Mathematics 2019-11-04 Ewan Davies , Matthew Jenssen , Will Perkins , Barnaby Roberts

We give the first construction of explicit constant-degree lossless vertex expanders. Specifically, for any $\varepsilon > 0$ and sufficiently large $d$, we give an explicit construction of an infinite family of $d$-regular graphs where…

Combinatorics · Mathematics 2025-04-22 Jun-Ting Hsieh , Alexander Lubotzky , Sidhanth Mohanty , Assaf Reiner , Rachel Yun Zhang

We develop a notion of containment for independent sets in hypergraphs. For every $r$-uniform hypergraph $G$, we find a relatively small collection $C$ of vertex subsets, such that every independent set of $G$ is contained within a member…

Combinatorics · Mathematics 2014-12-01 David Saxton , Andrew Thomason

We prove a far-reaching strengthening of Szemer\'edi's regularity lemma for intersection graphs of pseudo-segments. It shows that the vertex set of such a graph can be partitioned into a bounded number of parts of roughly the same size such…

Combinatorics · Mathematics 2023-12-05 Jacob Fox , Janos Pach , Andrew Suk

Let $i_t(G)$ denote the number of independent sets of size $t$ in a graph $G$. Levit and Mandrescu have conjectured that for all bipartite $G$ the sequence $(i_t(G))_{t \geq 0}$ (the {\em independent set sequence} of $G$) is unimodal. We…

Combinatorics · Mathematics 2012-06-15 David Galvin

The independence number of a hypergraph H is the size of a largest set of vertices containing no edge of H. In this paper, we prove new sharp bounds on the independence number of n-vertex (r+1)-uniform hypergraphs in which every r-element…

Combinatorics · Mathematics 2011-06-17 Alexander Kostochka , Dhruv Mubayi , Jacques Versatraete

In this paper, we study a bipartite analogue of the `random graphs evolving by degrees' process. We are given a bipartitioned set of vertices $V$ into two disjoint parts ${L}$ and ${R}$ and possibly unequal positive constants $\alpha$ and…

Probability · Mathematics 2025-09-30 Neeladri Maitra

Hypergraphs are an invaluable tool to understand many hidden patterns in large data sets. Among many ways to represent hypergraph, one useful representation is that of weighted clique expansion. In this paper, we consider this…

Combinatorics · Mathematics 2018-08-15 Ashwin Guha , Ambedkar Dukkipati
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