RT Journal Article T1 Orbital Hypernormal Forms A1 Algaba Durán, Antonio A1 Gamero, Estanislao A1 García García, Cristóbal AB In this paper, we analyze the problem of determining orbital hypernormal forms—that is, the simplest analytical expression that can be obtained for a given autonomous system around an isolated equilibrium point through time-reparametrizations and transformations in the state variables. We show that the computation of orbital hypernormal forms can be carried out degree by degree using quasi-homogeneous expansions of the vector field of the system by means of reduced time-reparametrizations and near-identity transformations, achieving an important reduction in the computational effort. Moreover, although the orbital hypernormal form procedure is essentially nonlinear in nature, our results show that orbital hypernormal forms are characterized by means of linear operators. Some applications are considered: the case of planar vector fields, with emphasis on a case of the Takens–Bogdanov singularity PB MDPI SN 2073-8994 (electrónico) YR 2021 FD 2021 LK http://hdl.handle.net/10272/20056 UL http://hdl.handle.net/10272/20056 LA eng NO Algaba, A., Gamero, E., & García, C. (2021). Orbital Hypernormal Forms. Symmetry, 13(8), 1500. https://doi.org/10.3390/sym13081500 DS Repositorio Institucional de la Universidad de Huelva RD 31 may 2026