Speaker
Description
We present a closed-form framework for the renormalized stress-energy tensor of a scalar quantum field in arbitrary $3+1$-dimensional curved spacetimes through a reformulation of the Hadamard scheme. This approach allows one to construct explicit expressions bypassing the standard mode-sum procedure and rendering the semiclassical field equations more tractable. As an application, we construct explicit families of renormalized stress-energy tensors in Schwarzschild spacetime, evaluated in Unruh-like and Boulware-like quantum states. The Unruh-like family encompasses the Hawking flux at infinity and the associated ingoing negative-energy flux at the horizon. Our results provide a new route to the study of semiclassical backreaction in four dimensions, extending to realistic spacetimes the level of analytical control previously available only in two-dimensional models.