Dynamical Electroweak Symmetry Breaking

These lectures explored the idea that the physics of electroweak symmetry breaking arises from novel strong dynamics. We started from the familiar strong-interaction dynamics of QCD, introduced simple dynamical electroweak symmetry breaking models whose strong dynamics imitate those of QCD, analyzed the limitations of these models, and finally moved on to theories whose dynamics differ from those of QCD in intriguing and useful ways. Because strong-dynamics models predict new states at accessible energies, experimental constraints have played a large role in the development of these theories. Accordingly, we discussed a number of specific classes of models that have been created to meet specific experimental challenges and examine their phenomenology. Some may ask why it is necessary to keep creating and studying new kinds of models, why the Standard Model and its supersymmetric extension(s) do not suffice. The answer, quite simply, is that we lack experimental evidence as to the mechanism of electroweak symmetry breaking. Theoretical arguments about which general kinds of mechanisms are plausible leave us with too many open possibilities, each with its own strengths and weaknesses. It is often pointed out that we need experimental data to winnow the options. At the same time, we must think carefully about what conclusions one will be able to draw from the data. For example, if a collider experiment