%0 Journal Article %T Asymmetry in Hilbert's fourth problem %A Juan-Carlos Alvarez Paiva %J Mathematics %D 2013 %I arXiv %X In the asymmetric setting, Hilbert's fourth problem asks to construct and study all (non-reversible) projective Finsler metrics: Finsler metrics defined on open, convex subsets of real projective $n$-space for which geodesics lie on projective lines. While asymmetric norms and Funk metrics provide many examples of essentially non-reversible projective metrics defined on proper convex subsets of projective $n$-space, it is shown that any projective Finsler metric defined on the whole projective $n$-space is the sum of a reversible projective metric and an exact 1-form. %U http://arxiv.org/abs/1301.2524v1