### Abstract

We consider the Hubbard model on a finite set of sites with nonpositive hopping matrix elements and infinitely strong on-site repulsion. Nagaoka's theorem states that in this model the relative ground state in the sector with one unoccupied site is maximally ferromagnetic. We show that this phenomenon is a consequence of a combinatorial coincidence valid in the one-hole regime only. In the case of more than one hole there is no reason to expect maximally ferromagnetic ground states. We prove this claim for the case of two holes for models defined on a class of graphs which contains all tori that are not too small. © 1991 Kluwer Academic Publishers.

Original language | English |
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Pages (from-to) | 321-333 |

Number of pages | 13 |

Journal | Letters in Mathematical Physics |

Volume | 22 |

Issue number | 4 |

DOIs | |

Publication status | Published - Aug 1991 |

### Keywords

- AMS subject classifications (1991): 81Q99, 81V70, 82B10

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## Cite this

Tóth, B. (1991). Failure of saturated ferromagnetism for the Hubbard model with two holes.

*Letters in Mathematical Physics*,*22*(4), 321-333. https://doi.org/10.1007/BF00405607