Higher-order corrections to BFKL evolution from t-channel unitarity

Using reggeon diagrams as a partial implementation of t-channel unitarity, O(g^4) corrections to the BFKL evolution equation have been obtained. We describe the spectrum and holomorphic factorization properties of the resulting scale-invariant kernel. For a gauge theory, t-channel unitarity can be studied directly in the complex j-plane by implementing Ward identity constraints together with the group structure of reggeon interactions. We discuss how both the O(g^2) BFKL kernel and the O(g^4) corrections can then be derived