Flavours of gauge theories

PhD ceremony: Mr. A. Deuzeman, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Title: Flavours of gauge theories

Promotor(s): prof. E. Pallante

Faculty: Mathematics and Natural Sciences

The introduction of fermionic degrees of freedom in non-Abelian gauge theories has the potential of substantially altering the gauge dynamics. This dissertation present the results of studies of SU(3) gauge theories with increasing fundamental quark content by means of lattice simulations. After an introduction to the effects of including dynamical quarks in lattice simulations, results on pioneering attempts of the inclusion of dynamical charm quarks in large scale lattice simulations are reported. Subsequent chapters move beyond phenomenology of the Standard Model, to study the effects of large numbers of light quark flavours. Results from perturbation theory suggest the possible appearance of a new phase in theories possessing more than a certain critical number of quark flavours. The appearance of such a phase potentially has a large impact on physics beyond the Standard Model, but the particular critical value of quark flavours and indeed the existence of such a phase itself have been disputed. Using methods inspired by the physics of phase transitions, the absence of such a novel phase in the case of eight quark flavours is shown. At twelve flavours, however, strong indications are found that the theory is no longer in the regular phase of QCD. Preliminary results on the properties of such a theory are presented.