Analysis of gauged Witten equation

The gauged Witten equation was essentially introduced by Witten in his formulation of gauged linear $\sigma$-model (GLSM). GLSM is a physics theory which explains the so-called Landau-Ginzburg/Calabi-Yau correspondence. This is the first paper in a series towards a mathematical construction of GLSM. In this paper we study some analytical properties of the gauged Witten equation for a Lagrange multiplier type superpotential. It contains the asymptotic property of finite energy solutions, the linear Fredholm property, the uniform $C^0$-bound, and the compactness of the moduli space of solutions over a fixed smooth $r$-spin curve with uniform energy bound.