First Dirichlet eigenvalue
= First Dirichlet eigenvalue
{c}
{title2=$\lambda_1$}
For a bounded domain $\Omega$, the first Dirichlet eigenvalue of $-\Delta$ has the variational characterization
$$
\lambda_1=\inf_{0\ne u\in H_0^1(\Omega)}
\frac{\int_\Omega|\nabla u|^2}{\int_\Omega|u|^2}.
$$