Amirkabir University of TechnologyAUT Journal of Mathematics and Computing2783-24492220211001Flag curvatures of the unit sphere in a Minkowski-Randers space275282445510.22060/ajmc.2021.20237.1061ENLibingHuangSchool of Mathematical Sciences, Nankai University, P.R.ChinaHaibinSuSchool of Mathematical Sciences, Nankai University, P. R. ChinaJournal Article20210705On a real vector space $V$, a Randers norm $hat{F}$ is defined by $hat{F}=hat{alpha}+hat{beta}$, where $hat{alpha}$ is a Euclidean norm and $hat{beta}$ is a covector. We show that the unit sphere $Sigma$ in the Randers space $(V,hat{F})$ has positive flag curvature, if and only if $|hat{beta}|_{hat{alpha}} < (5-sqrt{17})/2 approx 0.43845$, thus answering a problem proposed by Prof. Zhongmin Shen. Moreover, we prove that the flag curvature of $Sigma$ has a universal lower bound $-4$.https://ajmc.aut.ac.ir/article_4455_2addda78abe2b3690f74cd5756c7c2e8.pdf