Holomorphicity of Minimal Surfaces with Lagrangian Free Boundary
We study branched minimal immersions of compact bordered Riemann surfaces into almost K$ä$hler four-manifolds with free boundary on oriented Lagrangian surfaces. We establish a relative complex-point formula relating the Maslov index to complex and anticomplex tangency counts, and derive a sharp criterion for holomorphicity and area minimization in the relative homotopy class. If the ambient manifold is K$ä$hler-Einstein with positive Einstein constant and the supporting Lagrangian surface is minimal, then the immersion is holomorphic, antiholomorphic, or Lagrangian whenever cos $α$ does not change sign, where $α$ is the K$ä$hler angle. In the hyperk$ä$hler case, under the same boundary hypotheses, the absence of Lagrangian points implies holomorphicity with respect to one fixed parallel complex structure. We also extend Lichnerowicz's partial-energy homotopy identity to compact almost K$ä$hler domains with boundary mapped into a Lagrangian submanifold. Consequently, holomorphic and antiholomorphic maps minimize energy in their relative homotopy classes. Examples show that total reality cannot replace the Lagrangian boundary condition.