Universality in the Large N_c Dynamics of Flavour: Thermal Vs. Quantum Induced Phase Transitions

We show how two important types of phase transition in large N_c gauge theory with fundamental flavours can be cast into the same classifying framework as the meson-melting phase transition. These are quantum fluctuation induced transitions in the presence of an external electric field, or a chemical potential for R-charge. The classifying framework involves the study of the local geometry of a special D-brane embedding, which seeds a self-similar spiral structure in the space of embeddings. The properties of this spiral, characterized by a pair of numbers, capture some key universal features of the transition. Computing these numbers for these non-thermal cases, we find that these transitions are in the same universality class as each other, but have different universal features from the thermal case. We present a natural generalization that yields new universality classes that may pertain to other types of transition.