Positivity bounds from thermal field theory entropy

• URL: http://arxiv.org/abs/2509.06630v2
• Date: Fri, 12 Sep 2025 12:41:19 GMT
• Title: Positivity bounds from thermal field theory entropy
• Authors: Xin-Yi Liu, Yongjun Xu,
• Abstract summary: We compute the finite-temperature entropy using thermal field theory techniques.<n>We show that the coefficient of the leading dimension-8 operator must be strictly positive.
• Score: 13.657304740460683
• License: http://creativecommons.org/publicdomain/zero/1.0/
• Abstract: We present an approach to deriving positivity bounds on effective field theories by analyzing the thermodynamic behavior of thermal quantum field systems. Focusing on scalar theories with higher-dimensional operators, we compute the finite-temperature entropy using thermal field theory techniques. We argue that consistency with fundamental thermodynamic principles--specifically, the expectation that entropy increases with the introduction of new degrees of freedom--imposes nontrivial constraints on Wilson coefficients. In particular, we show that the coefficient of the leading dimension-8 operator must be strictly positive. This thermodynamic perspective offers an alternative to traditional S-matrix-based derivations of positivity bounds and provides a complementary perspective into the interplay between entropy, unitarity, and causality in quantum field theory.

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