Thomas Aaby Ryttov

Title: Conformal Dynamics for Electroweak Symmetry Breaking

A thesis submitted for the degree of Doctor of Philosophy on May, 2009.

Supervisor:
Francesco Sannino

Abstract

Conformal Dynamics for Electroweak Symmetry Breaking

This thesis discusses recent progress in the uncovering of the phase diagram of (non) supersymmetric gauge theories and possible applications for beyond Standard Model physics. We first introduce the phase diagram as a function of the number of colors, flavors and type of fermion representation before providing an estimate of the nonsupersymmetric conformal window using the ladder approximation. We then investigate the phase diagram of N = 1 supersymmetric gauge theories. Based on the supersymmetric analysis we propose an all-orders beta function for nonsupersymmetric gauge theories which allows us to bound the conformal window. We find that our prediction agrees with all recent lattice data.

The nature of the conformal window for higher dimensional representations suggests a possible way to construct realistic technicolor models. Two such explicit theories are then provided. The first is the Minimal Walking Technicolor model for which we derive the effective theory and investigate the prospects of gauge coupling unification. With a small modification of the Standard Model fermionic content we find that the coupling constants provide excellent unification. The second model is the Ultra Minimal Walking Technicolor model which consists of fermions belonging to two distinct representations of the gauge group. This model has a natural cold dark matter candidate which can be light enough to be detected at the LHC. We finally study the electroweak phase transition at finite temperature and find a very rich phase diagram.