Uniform positive scalar curvature from supercritical quadratic decay

Let $(M^n,g)$ be a complete connected noncompact smooth Riemannian manifold without boundary, with $n\ge 3$ and positive scalar curvature. We prove that $M$ admits a complete smooth metric of uniformly positive scalar curvature if $$\underset{d_g(o,x)\to \mathrm{\infty }}{\mathrm{lim\hspace{0.17em}inf}}{d}_g(o,x{)}^2{R}_g(x)>\frac{n-1}{n}$$ for a fixed point $o\in M$. This extends earlier existence results for orientable manifolds, due to Chen in dimension three and to the authors in dimensions $4\le n\le 7$, to every dimension $n\ge 3$ without an orientability assumption.