P. Duarte, PLENTY OF ELLIPTIC ISLANDS FOR THE STANDARD FAMILY OF AREA-PRESERVINGMAPS, Annales de l Institut Henri Poincare. Analyse non lineaire, 11(4), 1994, pp. 359-409
For the Standard Map, a well-known family of conservative diffeomorphi
sms on the torus, we construct large basic sets which fill in the toru
s as the parameter runs to infinity. Then we prove that, for a residua
l set of large parameters, these basic sets are accumulated by ellipti
c periodic islands. We also show that there exists a k0 > 0 and a dens
e set of parameters in [k0,infinity) for which the standard map exhibi
ts homoclinic tangencies.