%0 Journal Article %T A Fourth Order Curvature Flow on a CR 3-manifold %A Shu-Cheng Chang %A Jih-Hsin Cheng %A Hung-Lin Chiu %J Mathematics %D 2005 %I arXiv %X Let $(\mathbf{M}^{3},J,\theta_{0})$ be a closed pseudohermitian 3-manifold. Suppose the associated torsion vanishes and the associated $Q$-curvature has no kernel part with respect to the associated Paneitz operator. On such a background pseudohermitian 3-manifold, we study the change of the contact form according to a certain version of normalized $Q$-curvature flow. This is a fourth order evolution equation. We prove that the solution exists for all time and converges smoothly to a contact form of zero $Q$ -curvature. We also consider other background conditions and obtain a priori bounds up to high orders for the solution. %U http://arxiv.org/abs/math/0510494v1