| Time：1120927 (Wed.) 14:20~16:20 Speaker：Prof.張正宏(Cheng Hung Chang) 國立陽明交通大學物理研究所/Institute of Physics, National Yang Ming Chiao Tung University Title：Efficiencies of active heat engines Abstract：When Carnot and Stirling conceived their heat engines, temperature unambiguously represented the perceived cold and hot in our daily life. However, when this energy scale is extended to measure the noise strength of general non-equilibrium heat baths, such as those composed of bacteria or active particles, it deviates into different meanings. This raises the question of whether and how thermodynamic principles and conclusions would split beyond a unique definition of temperature. Here, this question is explored on the efficiency of a colloidal Stirling engine. We examine such engines governed by a large number of stochastic dynamical systems and extract and analyze those that can outperform their equilibrium limit in the thermal heat bath, as notably found in a recent experiment of bacterial baths. Physically, the observed high efficiency in those systems is ascribed to either a restoring effect in noise or a strong dissipation kernel, whereas mathematically it is caused by the enlarged dimension in the parameter space. The results reveal origins of high performance in stochastic heat engines, provide application strategies for harvesting energies from background noises, and, more fundamentally, introduce how the subtleties of nonequilibrium temperature enter stochastic thermodynamics, in addition to several other traditional subfields of physics. Place：S102, Gongguan Campus, NTNU |
