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We revisit results obtained in [F. Harary, U. Peled, Hamiltonian threshold graphs, Discrete Appl.~Math., 16 (1987), 11--15], where several necessary and necessary and sufficient conditions for a connected threshold graph to be Hamiltonian…

Combinatorics · Mathematics 2021-02-17 Milica Andelic , Tamara Koledin , Zoran Stanic

We say a graph $G$ has a Hamiltonian path if it has a path containing all vertices of $G$. For a graph $G$, let $\sigma_2(G)$ denote the minimum degree sum of two nonadjacent vertices of $G$; restrictions on $\sigma_2(G)$ are known as…

Combinatorics · Mathematics 2020-01-07 Ilkyoo Choi , Jinha Kim

In this paper, we study (zero) forcing sets which induce connected subgraphs of a graph. The minimum cardinality of such a set is called the connected forcing number of the graph. We provide sharp upper and lower bounds on the connected…

Combinatorics · Mathematics 2016-05-10 Randy Davila , Michael Henning , Colton Magnant , Ryan Pepper

A graph $G$ of order $2n$ is called degree-equipartite if for every $n$-element set $A\subseteq V(G)$, the degree sequences of the induced subgraphs $G[A]$ and $G[V(G)\setminus A]$ are the same. In this paper, we characterize all…

Combinatorics · Mathematics 2011-08-09 Khodakhast Bibak , Mohammad Hassan Shirdareh Haghighi

In this paper, we introduce the concept of curling subsequence of simple, finite and connected graphs. A curling subsequence is a maximal subsequence $C$ of the degree sequence of a simple connected graph $G$ for which the curling number…

Combinatorics · Mathematics 2015-07-08 Johan Kok , Naduvath Sudev , Chithra Sudev

By generalizing a recent result of Hong, Liu, and Lai on characterizing the degree-sequences of simple strongly connected directed graphs, a characterization is provided for degree-sequences of simple $k$-node-connected digraphs. More…

Combinatorics · Mathematics 2017-09-05 Kristóf Bérczi , András Frank

A sequence of nonnegative integers $\pi$ is {\it graphic} if it is the degree sequence of some graph $G$. In this case we say that $G$ is a \textit{realization} of $\pi$, and we write $\pi=\pi(G)$. A graphic sequence $\pi$ is {\it…

Combinatorics · Mathematics 2013-03-25 Catherine Erbes , Michael Ferrara , Ryan R. Martin , Paul Wenger

We study optimal minimum degree conditions when an $n$-vertex graph $G$ contains an $r$-regular $r$-connected subgraph. We prove for $r$ fixed and $n$ large the condition to be $\delta(G) \ge \frac{n+r-2}{2}$ when $nr \equiv 0 \pmod 2$.…

Combinatorics · Mathematics 2021-08-18 Max Hahn-Klimroth , Olaf Parczyk , Yury Person

A graph $G$ contains another graph $H$ as an immersion if $H$ can be obtained from a subgraph of $G$ by splitting off edges and removing isolated vertices. There is an obvious necessary degree condition for the immersion containment: if $G$…

Combinatorics · Mathematics 2022-09-27 Chun-Hung Liu

We give constructive proofs for the existence of uniquely hamiltonian graphs for various sets of degrees. We give constructions for all sets with minimum 2 (a trivial case added for completeness), all sets with minimum 3 that contain an…

Combinatorics · Mathematics 2024-12-04 Gunnar Brinkmann , Matthias De Pauw

Given a finite, simple graph $G$, the $k$-component order edge connectivity of $G$ is the minimum number of edges whose removal results in a subgraph for which every component has order at most $k-1$. In general, determining the…

Combinatorics · Mathematics 2023-10-10 Michael Yatauro

We give sufficient conditions under which a random graph with a specified degree sequence is symmetric or asymmetric. In the case of bounded degree sequences, our characterisation captures the phase transition of the symmetry of the random…

Combinatorics · Mathematics 2020-04-07 Lochlan Brick , Pu Gao , Angus Southwell

For integers $k \geq 2$ and $n \geq k+1$, we prove the following: If $n\cdot k$ is even, there is a connected $k$-regular graph on $n$ vertices. If $n\cdot k$ is odd, there is a connected nearly $k$-regular graph on $n$ vertices.

Combinatorics · Mathematics 2018-01-26 Ghurumuruhan Ganesan

Minimal prime graphs are connected graphs on at least two vertices whose complements satisfy the following conditions: triangle-freeness, 3-colorability, and edge-maximality with respect to the latter two properties. These graphs are prime…

Combinatorics · Mathematics 2025-12-19 Bryan Alvarez , Micah Dorton , Thomas Michael Keller , Lawrence Liu , Evan Zhang

Suppose a graph has no large balanced bicliques, but has large minimum degree. Then what can we say about its induced subgraphs? This question motivates the study of degree-boundedness, which is like $\chi$-boundedness but for minimum…

Combinatorics · Mathematics 2024-11-14 Xiying Du , Rose McCarty

The question whether there exists a hypergraph whose degrees are equal to a given sequence of integers is a well-known reconstruction problem in graph theory, which is motivated by discrete tomography. In this paper we approach the problem…

Combinatorics · Mathematics 2024-02-08 Michela Ascolese , Matthias Lienau , Matthias Schulte , Anusch Taraz

Bidirected graphs generalize directed and undirected graphs in that edges are oriented locally at every node. The natural notion of the degree of a node that takes into account (local) orientations is that of net-degree. In this paper, we…

Combinatorics · Mathematics 2017-04-11 Laura Gellert , Raman Sanyal

Simple necessary and sufficient conditions for a $n$-tuple of noncommutative polynomials to be a cyclic gradient are given and similarly for a noncommutative polynomial to have a vanishing cyclic gradient. Connections with free probability…

Rings and Algebras · Mathematics 2007-05-23 Dan Voiculescu

In an earlier work, finite groups whose power graphs are minimally edge connected have been classified. In this article, first we obtain a necessary and sufficient condition for an arbitrary graph to be minimally edge connected.…

Group Theory · Mathematics 2024-08-21 Parveen , Manisha , Jitender Kumar

A graph $G$ is called $k$-factor-critical if after deleting any $k$ vertices the remaining subgraph still has a perfect matching. Fan and Lin [Adv. in Appl. Math. 174 (2026) 103019] posed an adjacency spectral condition for a graph with…

Combinatorics · Mathematics 2026-05-27 Jiaxu Zhong , Yong Lu