William Allan Bardeen (born September 15, 1941, in Washington, Pennsylvania) is an American theoretical physicist who worked at the Fermi National Accelerator Laboratory.He is renowned for his foundational work onthe chiral anomaly (the Adler-Bardeen theorem), the Yang-Mills and gravitational anomalies, the development of quantum chromodynamicsand the scheme frequently used in perturbative analysis of experimentally observable processes such as deep inelastic scattering, high energy collisions and flavor changing processes.
He also played a major role in developing a theory ofdynamical breaking of electroweak symmetry via top quark condensates, leading to the first composite Higgs models. His work on the chiral symmetry breaking dynamics of heavy-light quark bound states correctly predicted abnormally long-lived resonances which are chiral symmetry partners of the ground states, such as the . He also developed an analytic, non-perturbative approach for the calculation of non-leptonic decays of Kaons, known as Dual QCD.