 Relative Fisher information

For sufficiently regular positive probability densities, this compares their spatial logarithmic derivatives. It is the dissipation functional for relative entropy under suitable diffusion equations. For standard Gaussian $g=\gamma$, it becomes $\int |\nabla \log f+v{|}^{2}f$, and in one dimension equals $\int |f^{\prime }{|}^2/f+\int v^{2}f-2$ at unit mass.