Topping's existence conjecture for Ricci flow on complete noncompact 3-manifolds

Let $(M^3,g_0)$ be a complete noncompact $3$-dimensional Riemannian manifold with nonnegative, possibly unbounded, Ricci curvature

$$\operatorname{Ric}(g_0)\geq 0.$$

Topping's Ricci-flow existence conjecture. The Ricci flow equation

$$\frac{\partial g}{\partial t}=-2\operatorname{Ric}(g),\qquad g(0)=g_0,$$

has a corresponding smooth solution $g(t)$ on $M^3\times[0,T)$ for some $T>0$, and $g(t)$ is complete and has nonnegative Ricci curvature for each $t\in[0,T)$. This extends Shi's existence theory beyond the bounded-curvature setting and is a special case of a conjecture attributed to Topping; the statement concerns preservation of completeness and nonnegative Ricci curvature despite initially unbounded curvature.