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DY: Fachverband Dynamik und Statistische Physik

DY 47: Statistical Physics: General I

DY 47.6: Vortrag

Donnerstag, 12. März 2026, 10:45–11:00, ZEU/0114

Work extraction from a single negative-temperature bath considered as a temperature gradient-driven heat flow — •Wolfgang Bauer — Dept. of Internal Medicine I, Comprehensive Heart Failure Centre, UKW, Würzburg, Germany — EPV, Institute of Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany}

Work can dissipate as heat within a bath. The reverse, i.e. extracting work from a thermal bath without changing the state of the working system contradicts the 2nd law of thermodynamics. However, this does not hold for a bath at negative absolute temperature. Our approach reconciles the 2nd law with sole work extraction from a bath at negative temperature. We consider not only a single, but rather a large assembly of working systems. Within the assembly the working systems may exchange mutually energy by weak thermal coupling. This assembly is now assigned from Shannon entropy a canonical temperature. While this framework may seem unconventional for macroscopic working machines, it naturally becomes clear for very small, molecular-scale machines. We show for paradigmatic examples of working machines, that their initial canonical temperature is positive. Consequently, sole extraction of work from a bath at negative temperature represents simply heat flow from a hot system (bath at negative temperature) to a cool system (assembly of working machines), consistent with the 2nd law of thermodynamics.

Keywords: Work extraction from a heat bath; negative temperature; 2nd law of thermodynamics