On the inertia of heat
Max-Planck-Institut für Gravitationsphysik, Am Mühlenberg 1, D-14476, Golm, Germany
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Accepted: 29 June 2012
Published online: 6 July 2012
Does heat have inertia? This question is at the core of a long-standing controversy on Eckart's dissipative relativistic hydrodynamics. Here I show that the troublesome inertial term in Eckart’s heat flux arises only if one insists on defining thermal diffusivity as a spacetime constant. I argue that this is not the most natural definition, and that all confusion disappears if one considers, instead, the space-dependent comoving diffusivity, in line with the fact that, in the presence of gravity, space is an inhomogeneous medium.
© Società Italiana di Fisica and Springer, 2012