Topology of Stokes Complex Related to a Polynomial Quadratic Differential : Phase Transitions and Number of Short Trajectories

Abstract

In this paper, we give a full description of the critical graph of the quadratic differential $\varpi_{a,\theta}$ defined on the Riemann sphere $\widehat{% %TCIMACRO{\U{2102} }% %BeginExpansion \mathbb{C} %EndExpansion }$ by $\varpi_{a,\theta}=-e^{2i\theta}\left( z-a\right) \left( z^{2}-1\right) dz^{2},$ where $\theta\in% %TCIMACRO{\U{211d} }% %BeginExpansion \mathbb{R} %EndExpansion ,$ and $a\in% %TCIMACRO{\U{2102} }% %BeginExpansion \mathbb{C} %EndExpansion .$. We prove that the existence and the number of short trajectories of $\varpi_{a,\theta}$ depend on the location of $a$ in certain curves defined on the complex plane as the level sets of some harmonic functions. More focus will be to the cases $\theta\in\left\{ 0,\pi/4\right\} .$ We investigate these classifications to study an inverse spectral problem related to the complex cubic oscillator for Schr\"{o}dinger equation.