Nonlinear Riemann-Hilbert problem for bordered Riemann surfaces
Miran Cerne
TL;DR
The paper extends the nonlinear Riemann-Hilbert problem to bordered Riemann surfaces, proving that for a $C^{k+1}$ family of Jordan curves $\{\gamma_z\}$ in $\mathbb{C}$ containing 0, there exists a holomorphic $f$ on a bordered surface $\Sigma$ with at most $2g+m-1$ zeros such that $f(z)\in\gamma_z$ on the boundary. The construction combines approximate disc-solving with a dbar-gluing approach, a Gromov compactness argument, and a Begehr-Efendiev implicit-function theorem to perturb to an exact solution, while carefully controlling the zero set via index considerations. The results yield divisor-related corollaries and embedding consequences for finitely connected planar domains, and the Appendix furnishes the necessary technical tools, including plurisubharmonic constructions, area-normalization arguments, and sharp a priori estimates. Overall, the work provides a rigorous nonlinear Riemann-Hilbert framework for bordered Riemann surfaces and connects to polynomial hull descriptions and embedding problems in several complex variables.
Abstract
Let S be a bordered Riemann surface with genus g and m boundary components. For a smooth family of smooth Jordan curves in the complex plane parametrized by the boundary of S and such that all curves contain 0 in their interior we show that there exists a holomorphic solution of the corresponding Riemann-Hilbert problem with at most 2g+m-1 zeros on S.
