%0 Journal Article %T Signed quivers, symmetric quivers, and root systems %A D. A. Shmelkin %J Mathematics %D 2003 %I arXiv %X We define a special sort of weighted oriented graphs, signed quivers. Each of these yields a symmetric quiver, i.e., a quiver endowed with an involutive anti-automorphism and the inherited signs. We develop a representation theory of symmetric quivers, in particular we describe the indecomposable symmetric representations. Their dimensions constitute root systems corresponding to certain symmetrizable generalized Cartan matrices. %U http://arxiv.org/abs/math/0309091v1