We prove the first bifurcation result of time quasi-periodic traveling wave solutions for space periodic water waves with vorticity. In particular, we prove the existence of small amplitude time quasi-periodic solutions of the gravity-capillary water waves equations with constant vorticity, for a bidimensional fluid over a flat bottom delimited by a space-periodic free interface. These quasi-periodic solutions exist for all the values of depth, gravity and vorticity, and restrict the surface tension to a Borel set of asymptotically full Lebesgue measure.

}, isbn = {1432-0673}, url = {https://doi.org/10.1007/s00205-021-01607-w}, author = {Massimiliano Berti and Luca Franzoi and Alberto Maspero} } @article {2019, title = {Reducibility for a fast-driven linear Klein{\textendash}Gordon equation}, volume = {198}, year = {2019}, month = {2019/08/01}, pages = {1407 - 1439}, abstract = {We prove a reducibility result for a linear Klein{\textendash}Gordon equation with a quasi-periodic driving on a compact interval with Dirichlet boundary conditions. No assumptions are made on the size of the driving; however, we require it to be fast oscillating. In particular, provided that the external frequency is sufficiently large and chosen from a Cantor set of large measure, the original equation is conjugated to a time-independent, diagonal one. We achieve this result in two steps. First, we perform a preliminary transformation, adapted to fast oscillating systems, which moves the original equation in a perturbative setting. Then, we show that this new equation can be put to constant coefficients by applying a KAM reducibility scheme, whose convergence requires a new type of Melnikov conditions.

}, isbn = {1618-1891}, url = {https://doi.org/10.1007/s10231-019-00823-2}, author = {Luca Franzoi and Alberto Maspero} }