Rigidity results with curvature conditions from Lichnerowicz Laplacian and applications
The Bochner technique is a classical tool in global differential geometry for proving vanishing and rigidity results by exploiting curvature conditions. Building on recent extensions of this method to complete non-compact settings by Petersen and Wink, we investigate $L^Q$-harmonic tensors with $Q>1$ governed by the Lichnerowicz Laplacian on complete Riemannian manifolds. Our results generalize Bochner-type theorems to the non-compact realm, revealing new geometric rigidity phenomena not visible in compact cases. We establish vanishing theorems under integral curvature bounds and weighted Poincaré inequalities, and derive conditions under which harmonic tensors must vanish. In particular, we show that on Ricci-flat or Einstein manifolds, curvature tensors such as $\mathrm{Rm}$ or the Weyl tensor $W$ vanish identically under natural $L^Q$-integrability and positivity assumptions on the curvature operator. These results imply strong rigidity: flatness in the Ricci-flat case and constant sectional curvature in the Einstein case. We further apply our framework to closed hypersurfaces in space forms and derive vanishing results for intermediate Betti numbers under positivity conditions on the second fundamental form. Finally, we extend our theory to asymptotically locally Euclidean (ALE) spaces, proving that harmonic Weyl tensors and Codazzi tensors must vanish under curvature positivity and decay conditions. Our analysis also links these results to ADM mass rigidity, establishing new obstructions to nontrivial decaying solutions on ALE 4-manifolds.