Remarks on Manifolds with Two-Sided Curvature Bounds

We discuss folklore statements about distance functions in manifolds with two-sided bounded curvature. The topics include regularity, subsets of positive reach and the cut locus.

Some local maximum principles along Ricci flows

In this work, we obtain a local maximum principle along the Ricci flow $g(t)$ under the condition that $\mathrm {Ric}(g(t))\le {\alpha } t^{-1}$ for $t>0$ for some constant ${\alpha }>0$ . As an application, we will prove that under this condition, various kinds of curvatures will still be nonnegative for $t>0$ , provided they are non-negative initially. These extend the corresponding known results for Ricci flows on compact manifolds or on complete noncompact manifolds with bounded curvature. By combining the above maximum principle with the Dirichlet heat kernel estimates, we also give a more direct proof of Hochard’s [15] localized version of a maximum principle by Bamler et al. [1] on the lower bound of different kinds of curvatures along the Ricci flows for $t>0$ .

Stabilization of the Ship Motion by Restricted Control

. The article presents an algorithm for controlling the motion of an insufficiently controlled ship along a trajectory with a continuous bounded curvature, based on the feedback linearization method. The algorithm allows restricting the control signal, while the state vector of the ship motion model does not approach the singularity point of the control law. The control algorithm returns the ship to the specified trajectory-attractor at any lateral deviation of the ship from the specified trajectory.