Measurable consequences of the local breakdown of the concept of temperature

¹ Institute of Thechnical Physics, DLR Stuttgart Pfaffenwaldring 38-40, D-70569 Stuttgart, Germany
² Institute of Theoretical Physics I, University of Stuttgart Pfaffenwaldring 57, D-70550 Stuttgart, Germany

Corresponding author: hartmann@theo1.physik.uni-stuttgart.de

Received: 22 October 2004
Accepted: 13 April 2005

Abstract

Local temperature defined by a local canonical state of the respective subsystem, does not always exist in quantum many-body systems. Here, we give some examples of how this breakdown of the temperature concept on small length scales might be observed in experiments: Measurements of magnetic properties of an anti-ferromagnetic spin-1 chain. We show that those magnetic properties are in fact strictly local. As a consequence, their measurement reveals whether the local (reduced) state can be thermal. If it is, a temperature may be associated to the measurement results, while this would lead to inconsistencies otherwise.