Date of Award

Spring 1-1-2014

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Anna Hasenfratz

Second Advisor

Thomas DeGrand

Third Advisor

Ethan Neil

Fourth Advisor

Oliver DeWolfe

Fifth Advisor

Zoltan Sternovsky


The discovery of the 125GeV Higgs resonance at the Large Hadron Collider in 2012 completed the electroweak sector of the Standard Model. As exciting as this discovery is, we still do not understand the underlying mechanism of electroweak symmetry breaking. Strongly interacting gauge-fermion systems are of interests as they can provide missing ultraviolet completion of the Standard Model. At present the most reliable way to investigate these strongly coupled systems is with lattice simulations.

In this dissertation I describe lattice studies of SU(3) gauge theories with many fermion flavors, in search of a viable candidate of composite Higgs models. We discovered a novel phase in the twelve and eight flavor systems which we believe to be a lattice artifact. Later we developed a universal method to extract the mass anomalous dimension from the eigenmode of the massless Dirac operator. Our method is validated on the four flavor QCD-like system, supported by the sixteen flavor infrared conformal system, and predicts the twelve flavor system is infrared conformal with mass anomalous dimension 0.235(27) at the infrared fixed point. A similar investigation of the eight flavor system shows walking behaviors. This method is universal and can be applied to any lattice model of interests.