| Abstract: | Non‐linear parametric resonances occur frequently in nature. Here we summarize how they can be studied by means of perturbative methods. We show in particular how resonances can affect the motion of a test particle orbiting in the vicinity of a compact object. These mathematical toy‐models .nd application in explaining the structure of the observed kHz Quasi‐Periodic Oscillations: we show which aspects of the reality naturally enter in the theory, and which one still remain a puzzle. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
