Flag Curvature Pinching Of The Unit Sphere In A Minkowski-Randers Space

On a real vector space,a Randers norm is defined by a Euclidean norm and a covec-tor.The unit sphere S~n in Randers space has induced Randers metric F = ?+?.Because ? is closed,F is projectively related to ?,and we can find the minimal and maxmal val-ues of F.So we can prove that the unit sphere in a Randers normed space is positively curved,if and only if the length of this covector is smaller than 0.43845.Moreover,when the length of this covector varies,we show that the flag curvature has a universal lower bond -4.