zero. The torque formation and changes in rotation state vary with the underlying geometry; for example, oblate or prolate ellipsoids lead to different torque effects. Sitarski (1995) controls the evolution of the spin axis with an additional parameter in a linear precession model. Whipple & Sekanina (1979) and subsequent authors, for example Sekanina (1981), Królikowska (1998), and Królikowska et al. (2001), study the evolution of the rotation axis for a nonspherical nucleus under the assumption of a forced precession model. Jorda & Gutiérrez (2002) and Gutiérrez et al. (2002) investigate the sublimation activity of irregularly shaped cometary nuclei. Kramer et al. (2019) develop a Fourier series-based approach to parametrize the observed torque variations of comet 67P/Churyumov-Gerasimenko (67P/C-G) in a body-fixed coordinate system and compared the observations with different sublimation models. Attree et al. (2019, 2023, 2024) discuss the evolution of the torque of comet 67P/C-G based on the geomorphological properties defined in Marschall et al. (2017). Davidsson & Gutiérrez (2004) approximate the surface of an ellipsoid with a triangular mesh and regionally weighted activity. Maquet et al. (2012) weight the sublimation activity based on latitudinal bands on an ellipsoid surface.
The sublimation of ice from a cometary nucleus transfers momentum from the nucleus to the surrounding space. The spatial integration over the momentum field on the surface results in nongravitational acceleration (NGA) and nongravitational torque (NGT) acting on the rigid body of the comet. The NGA leads to variations in osculating elements and in trajectories through the solar system, while the NGT changes the rotational angular momentum, and thus the rotation state of the nucleus. The overall magnitudes of the NGA and the NGT depend on the effective cross section of the nucleus illuminated by the sun. The significance of NGAs and in particular of NGTs for the change in the rotation state is pointed out by Whipple (1950). Nongravitational torques are investigated; for example, for comet 2P/Encke by Whipple & Sekanina (1979), for comet 22P/Kopff by Sekanina (1984), for comet 1P/Halley by Peale & Lissauer (1989), Julian (1990), and for Halley-like comets by Samarasinha & Belton (1995). For rotational dynamics of general comets, reviews are outlined by Samarasinha et al. (2004), Yeomans et al. (2004), and Knight et al. (2024). A rotating jet model on a spherical body used by Chesley & Yeomans (2004) features NGAs but NGTs are always
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The rotational dynamics of a cometary nucleus can be considered as the rotation of a rigid body, as is pointed out by Samarasinha et al. (2004).

Early approaches such as that of Whipple & Sekanina (1979) are restricted to simple rotations, which are principal axis rotations.

These are characterized as rotations around only one of the principal axes of the tensor of inertia.

In this situation the directions for the rotational angular momentum and for the angular velocity are the same as that of the principal axis.

A special case of a principal axis rotation is the state of lowest rotational energy for a prescribed angular momentum.

It is the rotation around the axis of the largest moment of inertia.

In general, a nucleus can be in a nonprincipal axis rotation where the vectors for rotational angular momentum and for angular velocity do not point into the same direction.

As is discussed by Julian (1987), Samarasinha & Belton (1995), Gutiérrez et al. (2003), and Knight et al. (2024), nonprincipal axis rotations can be in short axis mode or in long axis mode.

The lowest-energy state is the limiting case of a short axis mode.

As is described by Jewitt (1997) and Frouard & Efroimsky (2018), in the presence of any damping for kinetic energy, a cometary nucleus in an excited state (i.e., one that is above lowest energy) will always tend to reach a lowest-energy state.

The two comets 1P and 103P are regarded as undergoing nonprincipal axis rotation, with the possibility that other comets may also exhibit this behavior, as is proposed by Knight et al. (2024).

Conversely, the majority of comets do not exhibit indications of strongly excited rotation states.