Measure upper bounds of nodal sets of solutions to Dirichlet problem of Schrödinger equations

Abstract: In this paper, we focus on estimating measure upper bounds of nodal sets of solutions to the following boundary value problem \begin{equation*} \left{ \begin{array}{lll} \Delta u+Vu=0\quad \mbox{in}\ \Omega,\[2mm] u=0\quad \mbox{on}\ \partial\Omega, \end{array}\right. \end{equation*} where $V\in W^{1,\infty}(\Omega)$ is a potential and $\Omega\subset \mathbb{R}^n (n\geq2)$ is a bounded domain. We show that upper bounds on the $(n-1)$-dimensional Hausdorff measure of the nodal sets of $u$ in $\Omega$ is less than or equal to $$C\Big(1+\log\left(|\nabla V|{L^{\infty}(\Omega)}+1\right)\Big)\cdot\left(|V|{L^{\infty}(\Omega)}^{\frac{1}{2}}+|\nabla V|{L^{\infty}(\Omega)}^{\frac{1}{2}}+1\right),$$ provided $\partial\Omega$ is $C^{2}$-smooth and $V$ is analytic. Here $C$ is a positive constant depending only on $n$ and $\Omega$. In particular, if $|\nabla V|{L^{\infty}(\Omega)}$ is small, the measure upper bound of the of nodal set of $u$ is less than or equal to $C\left(|V|^{\frac{1}{2}}_{L^{\infty}(\Omega)}+1\right)$.