On the geometry, flows and visualization of singular complex analytic vector fields on Riemann surfaces

Abstract

Motivated by the wild behavior of isolated essential singularities in complex analysis, we study singular complex analytic vector fields $X$ on arbitrary Riemann surfaces $M$. By vector field singularities we understand zeros, poles, isolated essential singularities and accumulation points of the above kind. In this framework, a singular analytic vector field $X$ has canonically associated; a 1-form, a quadratic differential, a flat metric (with a geodesic foliation), a global distinguished parameter or $\mathbb{C}$-flow box $\Psi_X$, a Newton map $\Phi_X$, and a Riemann surface $\mathcal{R}_X$ arising from the maximal $\mathbb{C}$-flow of $X$. We show that every singular complex analytic vector field $X$ on a Riemann surface is in fact both a global pullback of the constant vector field under $\Psi_X$ and of the radial vector field on the sphere under $\Phi_X$. As a result of independent interest, we show that the maximal analytic continuation of the a local $\mathbb{C}$-flow of $X$ is univalued on the Riemann surface $\mathcal{R}_{X} \subset M \times \mathbb{C}_t$, where $\mathcal{R}_X$ is the graph of $\Psi_{X}$. Furthermore we explore the geometry of singular complex analytic vector fields and present a geometrical method that enables us to obtain the solution, without numerical integration, to the differential equation that provides the $\mathbb{C}$-flow of the vector field. We discuss the theory behind the method, its implementation, comparison with some integration-based techniques, as well as examples of the visualization of complex vector fields on the plane, sphere and torus. Applications to visualization of complex valued functions is discussed including some advantages between other methods.