Uniform circular motion in General Relativity: Existence and extendibility of the trajectories De la Fuente, Daniel Romero Sarabia, Alfonso Torres Villarroya, Pedro José The notion of uniform circular motion in a general spacetime is introduced as a particular case of a planar motion. The initial value problem of the corresponding di erential equation is analysed in detail. Geometrically, an observer which obeys a uniform circular motion is characterized as a Lorentzian helix. The completeness of its inextensible trajectories is studied in Generalized Robertson-Walker spacetimes and in a relevant family of pp-wave spacetimes. The results may be physically interpreted saying that, under reasonable assumptions, a uniformly circular observer lives forever in these spacetimes, providing the absence of the singularities de ned by these timelike curves. 2021-09-08T08:15:57Z 2021-09-08T08:15:57Z 2017 journal article De la Fuente, D., Romero Sarabia, A., Torres Villarroya, P.J. Uniform circular motion in General Relativity: Existence and extendibility of the trajectories. Classical Quantum Gravity, vol. 34, no. 12, pp. 125016, 23, 2017 http://hdl.handle.net/10481/70138 eng http://creativecommons.org/licenses/by-nc-nd/3.0/ open access Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License