Rigid motions in special relativity

As is well-known, the usual definition of rigid bodies is not possible in special relativity. However, special kinds of motions of extended objects will be shown to be possible so that these motions resemble those of rigid bodies in many respects. In contrast to the rigid-body motions in nonrelativistic cases, only the motions similar to translational ones are allowed. These rigid motions can be shown to correspond to the Fermi-Walker transportation.