Modulo factors with bounded degrees

TL;DR

This paper establishes new degree factorization results in highly edge-connected bipartite and general graphs, providing conditions for the existence of factors with prescribed degree congruences and divisibility properties.

Contribution

It introduces novel sufficient conditions for factors with degree constraints in highly edge-connected bipartite and general graphs, extending previous results.

Findings

Existence of factors with degree congruences in bipartite graphs under connectivity and degree conditions

Generalization of degree factorization results to non-bipartite graphs

Identification of highly edge-connected graphs admitting factors with degrees divisible by k

Abstract

Let $G$ be a bipartite graph with bipartition $(X,Y)$, let $k$ be a positive integer, and let $f:V(G)\rightarrow \{-1,\ldots, k-2\}$ be a mapping with $\sum_{v\in X}f(v) \stackrel{k}{\equiv}\sum_{v\in Y}f(v)$. In this paper, we show that if $G$ is essentially $(3k-3)$-edge-connected and for each vertex $v$, $d_G(v)\ge 2k-1+f(v)$, then it admits a factor $H$ such that for each vertex $v$, $d_H(v)\stackrel{k}{\equiv} f(v)$, and $$\lfloor\frac{d_G(v)}{2}\rfloor-(k-1)\le d_{H}(v)\le \lceil\frac{d_G(v)}{2}\rceil+k-1.$$ Next, we generalize this result to general graphs and derive sufficient conditions for a highly edge-connected general graph $G$ to have a factor $H$ such that for each vertex $v$, $d_H(v)\in \{f(v),f(v)+k\}$. Finally, we show that every $(4k-1)$-edge-connected essentially $(6k-7)$-edge-connected graph admits a bipartite factor whose degrees are positive and divisible by $k$.