We prove several differential
Harnack inequalities for positive solutions to nonlinear backward heat equations with
different potentials coupled with the Ricci flow. We also derive an interpolated
Harnack inequality for the nonlinear heat equation under the 𝜀-Ricci flow on a closed
surface. These new Harnack inequalities extend the previous differential
Harnack inequalities for linear heat equations with potentials under the Ricci
flow.