preprint

Inserted: 2 aug 2026

Year: 2026

Abstract:

Let $n\geq2$ and let $M^n$ be a closed connected smooth manifold. Let $R^γ(M)$ be the space of smooth Riemannian metrics $g$ on $M$ for which the generalized conformal Laplace operator $-γΔ_g+\mathrm{R}_g$ is strictly positive. We prove that if $n=2$ and $γ\ge0$, or if $n\ge3$ and $0\leq γ\leq 4(n-1)/(n-2)$, the inclusion $R^0(M)\hookrightarrow R^γ(M)$ is a homotopy equivalence, thus generalizing, to all dimensions and in the maximal range, the results of Botvinnik--Rosenberg and Li--Mantoulidis. Then, we prove that if $n\ge3$ and $γ>4(n-1)/(n-2)$, the space $R^γ(M)$ is contractible, and hence nonempty. This solves a homotopy-theoretic strengthening of a conjecture of Gromov (Conjecture 3, Section 6.1.2, "Four Lectures on Scalar Curvature") in the maximal possible coefficient range. Concerning Gromov's conjecture we also treat the equivariant case and the case of manifolds with boundary.