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[2204.01923] Algorithms for the ferromagnetic Potts model on expanders

 1 year ago
source link: https://arxiv.org/abs/2204.01923
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[Submitted on 5 Apr 2022 (v1), last revised 18 Sep 2022 (this version, v2)]

Algorithms for the ferromagnetic Potts model on expanders

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We give algorithms for approximating the partition function of the ferromagnetic Potts model on d-regular expanding graphs. We require much weaker expansion than in previous works; for example, the expansion exhibited by the hypercube suffices. The main improvements come from a significantly sharper analysis of standard polymer models, using extremal graph theory and applications of Karger's algorithm to counting cuts that may be of independent interest. It is #BIS-hard to approximate the partition function at low temperatures on bounded-degree graphs, so our algorithm can be seen as evidence that hard instances of #BIS are rare. We believe that these methods can shed more light on other important problems such as sub-exponential algorithms for approximate counting problems.

Comments: 27 pages; added Theorem 2 as separate statement; to appear in FOCS 2022
Subjects: Data Structures and Algorithms (cs.DS); Discrete Mathematics (cs.DM); Combinatorics (math.CO)
Cite as: arXiv:2204.01923 [cs.DS]
  (or arXiv:2204.01923v2 [cs.DS] for this version)
  https://doi.org/10.48550/arXiv.2204.01923

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