Principal Investigator Joern Dunkel
Einstein's theory of relativity assumes that particles cannot move faster than the speed of light. Standard descriptions of diffusion and Brownian motion processes are in conflict with this postulate. The latter fact is rather unproblematic in most terrestrial applications, but it may lead to inconsistencies in, for example, astrophysical applications if one wants to describe the quasi-random motion of particles in very hot plasmas. In recent years, we have studied different approaches towards formulating diffusion processes in a relativistically consistent manner. A closely related problem concerns the relativistic generalization of thermodynamics. Einstein's theory predicts that observers who are in relative motion measure different length and time intervals. Historically, there has been some debate as to whether or not this also applies to thermodynamics quantities. The problem can be traced to the fact that thermodynamics deals with extended systems which need to be handled with care in relativity. Recently, we proposed a resolution of several conceptual difficulties by introducing definitions of thermodynamic quantities that are guided by photographic measurements.