Rotational Behaviour of Comet Nuclei
Numerical experiments of the rotational behaviour of comet nuclei have been performed, including the Sun and Jupiter’s disturbing torques in the models. In a stable configuration, the solar torque induces great librations that remain unchanged along the orbit. A close approach with Jupiter can result in great changes on the rotational pattern because of the motion sensitivity to initial conditions. The unstable configuration is characterized by great librations of the nutation angle, and the existence of a possibly large chaotic zone in the phase space.
We study the effects of gluon radiation on top production and decay processes at an $e^+e^-$ collider.The matrix elements are computed without any approximations, using spinor techniques. We use a Monte Carlo event generator which takes into account the infrared singularity due to soft gluons and differences in kinematics associated with radiation in the production versus decay process. The calculation is illustrated for several strategies of top mass reconstruction.