Odd Cuts in Bipartite Grafts II: Structure and Universality of Decapital Distance Components
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| Format: | Preprint |
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2025
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| author | Kita, Nanao |
| author_facet | Kita, Nanao |
| contents | This paper is the second in a series of papers characterizing the maximum packing of \( T \)-cuts in bipartite grafts, following the first paper (N.~Kita, ``Tight cuts in bipartite grafts~I: Capital distance components,'' {arXiv:2202.00192v2}, 2022). Given a graft $(G, T)$, a minimum join $F$, and a specified vertex $r$ called the root, the distance components of $(G, T)$ are defined as subgraphs of $G$ determined by the distances induced by $F$. A distance component is called {\em capital} if it contains the root; otherwise, it is called {\em decapital}. In our first paper, we investigated the canonical structure of capital distance components in bipartite grafts, which can be described using the graft analogue of the Kotzig--Lovász decomposition. In this paper, we provide the counterpart structure for the decapital distance components. We also establish a necessary and sufficient condition for two vertices $r$ and $r'$ under which a decapital distance component with respect to root $r$ is also a decapital distance component with respect to root $r'$. As a consequence, we obtain that the total number of decapital distance components in a bipartite graft, taken over all choices of root, is equal to twice the number of edges in a minimum join of the graft. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_23973 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Odd Cuts in Bipartite Grafts II: Structure and Universality of Decapital Distance Components Kita, Nanao Combinatorics This paper is the second in a series of papers characterizing the maximum packing of \( T \)-cuts in bipartite grafts, following the first paper (N.~Kita, ``Tight cuts in bipartite grafts~I: Capital distance components,'' {arXiv:2202.00192v2}, 2022). Given a graft $(G, T)$, a minimum join $F$, and a specified vertex $r$ called the root, the distance components of $(G, T)$ are defined as subgraphs of $G$ determined by the distances induced by $F$. A distance component is called {\em capital} if it contains the root; otherwise, it is called {\em decapital}. In our first paper, we investigated the canonical structure of capital distance components in bipartite grafts, which can be described using the graft analogue of the Kotzig--Lovász decomposition. In this paper, we provide the counterpart structure for the decapital distance components. We also establish a necessary and sufficient condition for two vertices $r$ and $r'$ under which a decapital distance component with respect to root $r$ is also a decapital distance component with respect to root $r'$. As a consequence, we obtain that the total number of decapital distance components in a bipartite graft, taken over all choices of root, is equal to twice the number of edges in a minimum join of the graft. |
| title | Odd Cuts in Bipartite Grafts II: Structure and Universality of Decapital Distance Components |
| topic | Combinatorics |
| url | https://arxiv.org/abs/2503.23973 |