Complex structure of time-periodic solutions decoded in Poincaré-Lindstedt series: the cubic conformal wave equation on ${\mathbb{S}}^3$

This work explores the rich structure of spherically symmetric time-periodic solutions of the cubic conformal wave equation on ${\mathbb{S}}^3$. We discover that the families of solutions bifurcating from the eigenmodes of the linearised equation form patterns similar to the ones observed for the cubic wave equation. Alongside the Galerkin approaches, we study them using the new method based on the Padé approximants. To do so, we provide a rigorous perturbative construction of solutions. Due to the conformal symmetry, the solutions presented in this work serve as examples of large time-periodic solutions of the conformally coupled scalar field on the anti-de Sitter background.