| Abstract: | In this paper, the authors are concerned with the forced isochronousoscillators with a repulsive singularity and a bounded nonlinearity$$x' + V'(x) + g(x) = e(t,x,x'),$$where the assumptions on $V$, $g$ and $e$ are regular, describedprecisely in the introduction. Using a variant of Moser's twisttheorem of invariant curves, the authors show the existence ofquasi-periodic solutions and boundedness of all solutions. Thisextends the result of Liu to the case of the above system where $e$depends on the velocity. |
