Theory2021

1. Explain the concept of gauge theory. Give an interpretation in terms of connections. What are the main ingredients of a gauge theory? How can one build invariant quantities?
2. Explain how one constructs a Yang-Mills theory and the fundamental differences with QED.
3. What are the Ward-Slavnov-Taylor identities? How are they derived?
4. What is a factorisation theorem in QCD? How does it make short distance calculations possible?
5. In deep inelastic scattering, define the structural functions of the proton and explain the main ingredients of the parton model.
6. Explain what is meant by the evolution of the distribution functions and where it comes from.
7. Explain how the Glashow Lagrangian is constructed, what are its principal predictions and its drawbacks.
8. Explain the Brout-Englert-Higgs mechanism of the standard model, and its prediction. How does it relate to the Goldstone theorem?
9. Explain how fermion masses are introduced in the standard model, and what is meant by flavour mixing. What is the fundamental property that originates from these mixings?