Recurrent Trajectories and Finite Critical Trajectories of Quadratic Differentials on the Riemann Sphere

In this paper, the focus will be on both the existence and non-existence respectively of finite critical trajectories and recurrent trajectories of a quadratic differential on the Riemann sphere. We show the connection between these two items. More precisely, we collect some criterions for the non-existence of recurrent trajectories. The first criterion is in the same vein of Jenkins Three-pole Theorem, while the second one is in relation with the so-called Level function of quadratic differentials.