What are you trying to do with this? The parentheses don’t balance, but if they did, perhaps it would be log-affine. In any event, please read the Geometric Programming section of the CVX User’s Guide http://cvxr.com/cvx/doc/gp.html as well as the CVX FAQ Why isn’t CVX accepting my model? READ THIS FIRST! to make sure you are following CVX’s rules.
Edit: I found another post by you, waiting for moderator approval, which now immediately precedes this post. The objective function in that post violates CVX’s DCP rules, as described in the CVX Users’ Guide, and so I will presume it is non-convex.