Title: On periodic solutions of nonlinear wave equations, including Einstein equations with a negative cosmological constant,
Abstract: We construct periodic solutions of nonlinear wave equations using analytic
continuation. The construction applies in particular to Einstein equations,
leading to infinite-dimensional families of time-periodic solutions of the
vacuum, or of the Einstein-Maxwell-dilaton-scalar
fields-Yang-Mills-Higgs-Chern-Simons-$f(R)$ equations, with a negative
cosmological constant.