2014/10/22 by L. Filipe Costa, José Natário · 1 voice · 3 citations
Physics and Astronomy · #gr-qc #hep-th
paper · pdf · doi:10.1007/978-3-319-18335-0_6
published as Fundamental Theories of Physics 179 (2015), 215-258 · 45 pages, 7 figures. Some minor improvements, typos fixed, signs in some expressions corrected. Matches the published version. Published as part of the book "Equations of Motion in Relativistic Gravity", D. Puetzfeld et al. (eds.), Fundamental Theories of Physics 179, Springer, 2015
arxiv published 2014/10/22 · arxiv created 2015/09/03 · arxiv updated 2015/09/03
We discuss the problem of defining the center of mass in general relativity and the so-called spin supplementary condition. The different spin conditions in the literature, their physical significance, and the momentum-velocity relation for each of them are analyzed in depth. The reason for the non-parallelism between the velocity and the momentum, and the concept of "hidden momentum", are dissected. It is argued that the different solutions allowed by the different spin conditions are equally valid descriptions for the motion of a given test body, and their equivalence is shown to dipole order in curved spacetime. These different descriptions are compared in simple examples.