Electronic Journal of Differential Equations, Vol. 2013 (2013), No. 259, pp. 1-12. Title: Existence of solutions for fractional Hamiltonian systems Author: Cesar Torres (Univ. de Chile, Santiago, Chile) Abstract: In this work we prove the existence of solutions for the fractional differential equation $$ _{t}D_{\infty}^{\alpha}(_{-\infty}D_{t}^{\alpha}u(t)) + L(t)u(t) = \nabla W(t,u(t)),\quad u\in H^{\alpha}(\mathbb{R}, \mathbb{R}^{N}). $$ where $\alpha \in (1/2, 1)$. Assuming L is coercive at infinity we show that this equation has at least one nontrivial solution. Submitted June 10, 2013. Published November 26, 2013. Math Subject Classifications: 26A33, 34C37, 35A15, 35B38. Key Words: Liouville-Weyl fractional derivative; fractional Hamiltonian systems; critical point; variational methods.