2026-02-04 茨城大学
図 1 左：通常の重力下では液体が下に沈む。右：無重力下で温度勾配を与えると、冷たい側に液体が集まる。
＜関連情報＞
- https://www.ibaraki.ac.jp/news/n/2026/02/04014500.html
- https://www.ibaraki.ac.jp/news/uploads/2026/02/Pressrelease_nakagawa_260204.pdf
- https://journals.aps.org/prl/abstract/10.1103/bbqy-hptc
熱力学の変分原理：重力と熱流を統一する Thermodynamic Variational Principle Unifying Gravity and Heat Flow
Naoko Nakagawa,Shin-ichi Sasa
Physical Review Letters Published: 3 February, 2026
DOI: https://doi.org/10.1103/bbqy-hptc
Abstract
Predicting the stable phase configuration in a liquid-gas system becomes a fundamental challenge when the stratification favored by gravity conflicts with arrangements induced by heat flow, particularly because standard equilibrium thermodynamics is insufficient in such nonequilibrium steady states. We propose a variational principle based on an extended thermodynamics, called global thermodynamics, to address this state selection problem. Our key finding is that gravity and heat flow effects are unified into a single parameter, “effective gravity” (eff), within this framework. Crucially, the sign of eff determines the stable configuration: liquid is at the bottom if eff>0, and floats above the gas if eff<0. This provides a quantitative tool for the configuration prediction under competing drives.
