Ethan Neil

Quantum chromodynamics (QCD), the theory which governs strong nuclear interactions and an integral part of the standard model, is the only known example in nature of a strongly-coupled Yang-Mills gauge theory One of the defining features of QCD is spontaneous breaking of chiral symmetry, which leads to a spectrum of low-lying meson states that can be understood as approximate Goldstone bosons associated with the symmetry breaking This phenomenon can also be used as the foundation for models of dynamical electroweak symmetry breaking, sometimes known as technicolor models, which provide an attractive alternative to the standard model Higgs sector However, attempts to construct realistic theories based on QCD have proven quite difficult QCD lies m a larger parameter space of Yang-Mills gauge theories, and a deeper understanding of this class of theories, m particular of the dependence on the number of light fermions N_f, may be essential for understanding physics beyond the standard model As such theories are strongly coupled, non-perturbative methods are required in order to make significant progress Here, I present the results of lattice gauge theory simulations which investigate the N_f dependence of Yang-Mills theories with gauge group SU(3), with particular focus on the transition from confining to conformal long-distance behavior.