Elliptic Schr\"odinger equations with gradient-dependent nonlinearity and Hardy potential singular on manifolds

Let $\Omega \subset \mathbb{R}^N$ ($N \geq 3$) be a $C^2$ bounded domain and $\Sigma \subset \Omega$ is a $C^2$ compact boundaryless submanifold in $\mathbb{R}^N$ of dimension $k$, $0\leq k < N-2$. For $\mu\leq (\frac{N-k-2}{2})^2$, put $L_\mu := \Delta + \mu d_{\Sigma}^{-2}$ where $d_{\Sigma}(x) = \mathrm{dist}(x,\Sigma)$. We study boundary value problems for equation $-L_\mu u = g(u,|\nabla u|)$ in $\Omega \setminus \Sigma$, subject to the boundary condition $u=\nu$ on $\partial \Omega \cup \Sigma$, where $g: \mathbb{R} \times \mathbb{R}_+ \to \mathbb{R}_+$ is a continuous and nondecreasing function with $g(0,0)=0$, $\nu$ is a given nonnegative measure on $\partial \Omega \cup \Sigma$. When $g$ satisfies a so-called subcritical integral condition, we establish an existence result for the problem under a smallness assumption on $\nu$. If $g(u,|\nabla u|) = |u|^p|\nabla u|^q$, there are ranges of $p,q$, called subcritical ranges, for which the subcritical integral condition is satisfied, hence the problem admits a solution. Beyond these ranges, where the subcritical integral condition may be violated, we establish various criteria on $\nu$ for the existence of a solution to the problem expressed in terms of appropriate Bessel capacities.