Twisted $S^1$ stability and positive scalar curvature obstruction on fiber bundles

Abstract: We establish several non-existence results of positive scalar curvature (PSC) on fiber bundles. We show under an incompressible condition of the fiber, for $X^m$ a Cartan-Hadamard manifold or an aspherical manifold when $m=3$, the fiber bundle over $X^m#M^m$ ($m\ge 3$) with $K(\pi,1)$ fiber, $NPSC^+$(a manifold class including enlargeable and Schoen-Yau-Schick ones) fiber, or spin fiber of non-vanishing Rosenberg index carries no PSC metric, with necessary dimension and spin compactible condition imposed. Furthermore, we show under a homotopically nontrivial condition of the fiber, the $S^1$ principle bundle over a closed 3-manifold admits PSC metric if and only if its base space does. These partially answer a question of Gromov and extend some previous results of Hanke, Schick and Zeidler concerning PSC obstruction on fiber bundles.