Renato C. Calleja, Alessandra Celletti, Rafael de la Llave
Existence of whiskered KAM tori of conformally symplectic systems
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ABSTRACT.  Many physical problems are described by conformally symplectic 
systems (i.e., systems whose evolution in time 
transforms a symplectic form into a multiple of itself). 
We study the existence of whiskered tori in 
a family $f_\mu$ of conformally symplectic maps depending on parameters $\mu$ 
(often called \emph{drifts}). We recall that whiskered tori 
are tori on which the motion is a rotation, but they 
have as many expanding/contracting directions as allowed by the 
preservation of the geometric structure. 
Our main result is formulated in an \emph{a-posteriori} format. 
We fix $\omega$ 
satisfying Diophantine conditions. We assume 
that we are given 1) a value of the 
parameter $\mu_0$, 2) an embedding of the torus $K_0$ into the 
phase space, approximately invariant under $f_{\mu_0}$ in the sense 
that $f_{\mu_0}