Bounded-cycle 2-factor conjecture under degree-sum and independent-set conditions

Let kk be a positive integer and let GG be a graph of order nn. For an independent set of order k+1k+1, define

σk+1(G):=min{vIdG(v)  |  I is an independent set of order k+1 of G},\sigma_{k+1}(G):=\min\left\{\sum_{v\in I}d_G(v)\;\middle|\; I\text{ is an independent set of order }k+1\text{ of }G\right\},

when α(G)k+1\alpha(G)\geq k+1, and set σk+1(G)=\sigma_{k+1}(G)=\infty otherwise. For an independent set II of GG, let δG(I)\delta_G(I) be the minimum degree of a vertex in II. A 2-factor is a 22-regular spanning subgraph. Bounded-cycle 2-factor conjecture. If

σk+1(G)n\sigma_{k+1}(G)\geq n

and every independent set II of GG satisfies

IδG(I)1,|I|\leq \delta_G(I)-1,

then GG has a 22-factor with at most kk cycles. The paper presents this as a conjecture on strengthening a 2-factor existence theorem to control the number of cycles; the source does not specify its resolution status.

Sources & referencesView supporting material

Primary source

Masaki Kashima, “Degree sum conditions and a 2-factor with a bounded number of cycles in claw-free graphs”, arXiv:2504.08268 (2025).

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