Quantum Response Theory and Momentum-Space Gravity

We present a quantum response approach to momentum-space gravity in dissipative multiband systems, which dresses both the quantum geometry-through an interband Weyl transformation-and the equations of motion. In addition to clarifying the roles of the contorsion and symplectic terms, we introduce the three-state quantum geometric tensor as a necessary element in the geometric classification of nonlinear responses and discuss the significance of the emergent terms from a gravitational point of view. We also identify a dual quantum geometric drag force in momentum space that provides an entropic source term for the multiband matrix of Einstein field equations.