Nonnegative solutions of an indefinite sublinear Robin problem I: positivity, exact multiplicity, and existence of a subcontinuum

Uriel Kaufmann, Humberto Ramos Quoirin, Kenichiro Umezu

Let $\Omega \subset {\mathbb{R}}^N$ ($N\ge 1$) be a smooth bounded domain, $a\in C(\bar{\Omega })$ a sign-changing function, and $0\le q<1$. We investigate the Robin problem \[ \begin{cases} -Δu…