Gehring Link Problem, Focal Radius and Over-torical width

英文摘要：

In this note, we study the Gehring link problem in the round sphere, which motives our study of the width of a band in positively curved manifolds. Using the same idea, we are able to get a sphere theorem for hypersurface in in the round $S^{n}$ in terms of its focal radius as well as the rigidity of Clifford hypersurface in $S^{n}$. The $3$-dimension case of our theorems confirm two conjectures raised by Gromov in [Gro18].