Department of Mathematics;
Central China Normal University;
Wuhan;
430079;
Department of Mathematics;
Unversity of Science and Technology of China;
Hefie;
230026;
Department of Mathematics;
Unversity of Science and Technology of China;
Hefie;
230026;
开流形; 非负Ricci曲率; 大体积增长条件; 临界半径; Petersen猜想; Riemann流形; Busemann函数;