On the Extension of Ricci Harmonic Flow

In this paper, we consider the extension problem of Ricci harmonic flow. On one hand, using the method of blowing up, we prove Ricci harmonic flow can be extended if Ln+22 norm of Riemannian curvature operator on M× [0 , T) is bounded. On the other hand, we establish L^∞ bound for nonnegative subsolution to linear parabolic equation, as an application, we prove that Ricci harmonic flow can be extended if Ln+22 norm of scalar curvature on M× [0 , T) is bounded and Ricci curvature has a uniform lower bound.