Semiclassical Backreaction of Massive Quantum Fields in the Spacetime of a Global Monopole

We study the leading semiclassical backreaction of massive scalar, spinor, and vector fields in the spacetime of a pointlike global monopole. Starting from the renormalized stress-energy tensors obtained in the Schwinger--DeWitt approximation, we derive the first-order semiclassical geometry generated by a general conserved diagonal source and then specialize it to fields of spin $0$, $1/2$, and $1$. The locally fixed quantum source falls as $r^{-6}$ and induces metric corrections of order $r^{-4}$. The scalar field generically produces distinct temporal and radial metric functions, whereas the spinor and vector fields lead to one-function geometries. We analyze the resulting curvature correction, the acceleration of static observers, geodesic motion, and the validity domain of the first-order solution. The quantum backreaction produces a local deformation of the monopole exterior but does not modify its asymptotic solid-angle deficit.