Prescribed mean curvature problems on homogeneous vector bundles

In this paper, we provide a detailed and systematic study of weak (singular) Hermite-Einstein structures on homogeneous holomorphic vector bundles over rational homogeneous varieties. We use standard tools from spectral geometry, Harmonic analysis, and Cartan's highest weight theory to provide a sufficient condition in terms of Fourier series and intersection numbers under which an L^2-function can be realized as mean curvature of a singular Hermitian structure on an irreducible homogeneous holomorphic vector bundle. We prove that the condition provided is necessary and sufficient for functions that belong to certain interpolation spaces. In the particular case of line bundles over irreducible Hermitian symmetric spaces of compact type, we describe explicitly in terms of representation theory the solutions of the underlying geometric PDE. Also, we establish a sufficient condition in terms of Fourier coefficients and intersection numbers for solvability and convergence of the weak Hermite-Einstein flow on irreducible homogeneous holomorphic vector bundles. As an application of our methods, we describe the first explicit examples in the literature of solutions to several geometric flows, including Donaldson's heat flow, Yang-Mills heat flow, and the gradient flow of Donaldson's Lagrangian, on line bundles over irreducible Hermitian symmetric spaces of compact type. Additionally, we show that every polynomial central charge function gives rise to a weak Donaldson's Lagrangian M. In the particular case of irreducible homogeneous holomorphic vector bundles, we prove that the gradient flow of M converges to a Hermitian structure which is, up to a gauge transformation, a Z-critical Hermitian structure in the large volume limit.