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PreprintCC BY 4.0arXiv

Perfect matchings in hypergraphs and Feige's inequality

Abstract

How large of a minimum degree does an n-vertex graph need before we are sure that it contains a perfect matching? Dirac's theorem states that a graph on an even number of vertices in which each vertex has degree at least n/2 has this property. In this short expository note, intended to be used in the classroom, we discuss how this statement generalizes to hypergraphs. In particular, we highlight an elegant connection between fractional perfect matchings in hypergraphs and a probabilistic inequality about nonnegative random variables, which was conjectured by Feige. We also present a very short self-contained proof of Feige's conjecture.

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BibTeX
@misc{milojevic2026perfect,
  title = {{Perfect matchings in hypergraphs and Feige's inequality}},
  author = {Aleksa Milojević and Benny Sudakov},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.10380},
  eprint = {2610.10380},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.10380},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Perfect matchings in hypergraphs and Feige's inequality
AU  - Aleksa Milojević
AU  - Benny Sudakov
PY  - 2026
DA  - 2026/10/07
PB  - arXiv
DO  - 10.48550/arxiv.2610.10380
UR  - https://arxiv.org/abs/2610.10380
AB  - How large of a minimum degree does an n-vertex graph need before we are sure that it contains a perfect matching? Dirac's theorem states that a graph on an even number of vertices in which each vertex has degree at least n/2 has this property. In this short expository note, intended to be used in the classroom, we discuss how this statement generalizes to hypergraphs. In particular, we highlight an elegant connection between fractional perfect matchings in hypergraphs and a probabilistic inequality about nonnegative random variables, which was conjectured by Feige. We also present a very short self-contained proof of Feige's conjecture.
ER  -