Volume 85, Number 1, January 2009
Article Number 10006
Number of page(s) 5
Section General
Published online 19 January 2009
EPL, 85 (2009) 10006
DOI: 10.1209/0295-5075/85/10006

Shannon meets Carnot: Generalized second thermodynamic law

O. Shental1 and I. Kanter2

1   Center for Magnetic Recording Research, University of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093, USA
2   Department of Physics, Bar-Ilan University - Ramat-Gan, 52900 Israel

received 6 August 2008; accepted in final form 7 December 2008; published January 2009
published online 19 January 2009

The classical thermodynamic laws fail to capture the behavior of systems with the energy Hamiltonian being an explicit function of the temperature. Such Hamiltonian arises, for example, in modeling information processing systems, like communication channels, as thermal systems. Here we generalize the second thermodynamic law to encompass systems with temperature-dependent energy levels, ${\rm d}Q=T{\rm d}S+\langle {\rm d}\mathcal{E}/{\rm d}T\rangle {\rm d} T $, where $\langle \cdot \rangle $ denotes averaging over the Boltzmann distribution and reveal a new definition to the basic notion of temperature. Furthermore, it is shown that the principles of the traditional thermodynamic framework are maintained, e.g., two systems in equilibrium have the same generalized temperature and heat always flows from high to low generalized temperature. This generalization enables to express, for instance, the mutual information of the Gaussian channel as a consequence of the laws of nature —the laws of thermodynamics.

05.70.-a - Thermodynamics.
89.70.Cf - Entropy and other measures of information.
89.70.Kn - Channel capacity and error-correcting codes.

© EPLA 2009