Approximating independent set in perturbed graphs

For the maximum independent set problem, strong inapproximability bounds for worst-case efficient algorithms exist. We give a deterministic algorithm beating these bounds, with polynomial expected running-time for semi-random graphs: an adversary chooses a graph with n vertices, and then edges are flipped with a probability of epsilon. Our algorithm guarantees an approximation ratio of Omikron(root of n epsilon) for sufficiently large epsilon .