Toward a Complexity Classification of High-Temperature Bosons: Computational Tractability and Power-Law Clustering

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Hauptverfasser: Tong, Xin-Hai, Kuwahara, Tomotaka
Format: Preprint
Veröffentlicht: 2025
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author Tong, Xin-Hai
Kuwahara, Tomotaka
author_facet Tong, Xin-Hai
Kuwahara, Tomotaka
contents Determining when quantum many-body systems admit simple, efficiently simulable structure is a central problem. High-temperature thermal states are a natural candidate for such simplicity, yet for bosons, the unbounded local Hilbert space and energy invalidate the usual expectation that large $T$ guarantees tractability. Here we investigate the resulting complexity boundary for interacting lattice bosons and show that the repulsive Bose--Hubbard class lies on the ``simple'' side. For a family with long-range hopping decaying as $r^{-α}$, we prove convergence of a controlled cluster expansion, which implies (above an explicit temperature threshold) an efficient classical algorithm to approximate the partition function and a rigorous power-law clustering bound for connected correlations. More broadly, our results provide a first step toward charting complexity boundaries for high-temperature bosons and suggest the repulsive Bose--Hubbard class as a natural candidate cusp.
format Preprint
id arxiv_https___arxiv_org_abs_2509_25572
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Toward a Complexity Classification of High-Temperature Bosons: Computational Tractability and Power-Law Clustering
Tong, Xin-Hai
Kuwahara, Tomotaka
Quantum Physics
Statistical Mechanics
Mathematical Physics
Determining when quantum many-body systems admit simple, efficiently simulable structure is a central problem. High-temperature thermal states are a natural candidate for such simplicity, yet for bosons, the unbounded local Hilbert space and energy invalidate the usual expectation that large $T$ guarantees tractability. Here we investigate the resulting complexity boundary for interacting lattice bosons and show that the repulsive Bose--Hubbard class lies on the ``simple'' side. For a family with long-range hopping decaying as $r^{-α}$, we prove convergence of a controlled cluster expansion, which implies (above an explicit temperature threshold) an efficient classical algorithm to approximate the partition function and a rigorous power-law clustering bound for connected correlations. More broadly, our results provide a first step toward charting complexity boundaries for high-temperature bosons and suggest the repulsive Bose--Hubbard class as a natural candidate cusp.
title Toward a Complexity Classification of High-Temperature Bosons: Computational Tractability and Power-Law Clustering
topic Quantum Physics
Statistical Mechanics
Mathematical Physics
url https://arxiv.org/abs/2509.25572