  Using a continuous unitary transformation recently proposed by Wegner
\cite{Wegner} together with an approximation that neglects irrelevant
contributions, we obtain flow equations for Hamiltonians. These flow equations
yield a diagonal or almost diagonal Hamiltonian. As an example we investigate
the Anderson Hamiltonian for dilute magnetic alloys. We study the different
fixed points of the flow equations and the corresponding relevant, marginal or
irrelevant contributions. Our results are consistent with results obtained by a
numerical renormalization group method, but our approach is considerably
simpler.
