Amirkabir University of TechnologyAUT Journal of Mathematics and Computing2783-24492220210901Flag curvatures of the unit sphere in a Minkowski-Randers space275282445510.22060/ajmc.2021.20237.1061ENLibingHuangSchool of Mathematical Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, P. R. ChinaHaibinSuSchool of Mathematical Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, 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_f64762c61fdb049d32c8804aebd40218.pdf