On the nature of thermodynamic extremum principles: The case of maximum efficiency and maximum work


  • In honour of Max Planck (1858–1947) on the occasion of his 150th birthday.


Extremum principles are at the heart of theoretical physics. For a complete definition one does not only need to specify the variable to be extremized but also the respective functional space and its parametrization. Here we use a control-theoretical approach to clarify the meaning of two maximum principles in the context of cyclic thermodynamic processes.