English

Packing spanning arborescences with extra large one

Combinatorics 2025-11-25 v1

Abstract

The celebrated Nash-Williams and Tutte's theorem states that a graph G=(V,E)G=(V, E) contains kk edge disjoint spanning trees if and only if νf(G)k\nu_{f}(G) \geq k, where νf(G):=minP>1,P is a partition of V(G)E(P)P1.\nu_{f}(G):=\min_{|\mathcal{\mathcal{P}}|>1, \text{$\mathcal{P}$ is a partition of $V(G)$}}\frac{|E( \mathcal{P})|}{|\mathcal{P}|-1}. Inspired by the NDT theorem as structural explanations for the fractional part of Nash-Williams' forest decomposition theorem, Fang and Yang extended Nash-Williams and Tutte's theorem and proved that if νf(G)>k+d1d\nu_{f}(G) > k+ \frac{d-1}{d}, then GG contains kk edge disjoint spanning trees and another forest FF with E(F)>d1d(V(G)1) |E(F)|> \frac{d-1}{d} (|V(G)|-1)|, and if FF is not a spanning tree, then FF has a component with at least dd edges. In this paper, we give a digraphic version of their result; however, the mixed graphic version remains open.

Keywords

Cite

@article{arxiv.2511.18952,
  title  = {Packing spanning arborescences with extra large one},
  author = {Hui Gao},
  journal= {arXiv preprint arXiv:2511.18952},
  year   = {2025}
}
R2 v1 2026-07-01T07:51:51.149Z