Is Temperature a Local Realistic Variable?

Temperature is conventionally defined in terms of the number of "possible" microstates, given a set of macroscopic constraints such as total energy, volume and particle number. It is a remarkable achievement of statistical mechanics, that an information theoretical, combinatoric quantity can connect so well to physical observables, such as the hight of a mercury collumn, or the volume of a baloon. In this talk, we depart from this succesfull tradition. We start with the simple observation that if a large but finite system is split into two subsystems, their temperatures get entangled. As such, an operator description of temperature becomes necessary to avoid an EPR-type causality violation. In this new picture, temperature is subject to the constraints of quantum mechanics, where its measurement must necessarily accompany a wavefunction collapse into a "temperature eigenstate". Finally, we briefly discuss the experimental implications of this alternative, questionable view.