Saba Baig Final Defense

Abstract: Quantum field theories are the fundamental framework for describing both high-energy particle interactions and low-energy emergent phenomena in condensed matter systems. Conformal field theories, a scale-invariant subclass, play a central role, particularly in two dimensions, where their infinite-dimensional conformal symmetry enables powerful analytic control. 2d CFTs serve as exactly solvable models of strong interactions and as boundary descriptions of gravitational theories in holographic dualities such as AdS/CFT. Conformal interfaces provide a natural setting to explore the nontrivial dynamical and structural features of irrational 2d CFTs, by probing how energy and information propagate across such interfaces. This thesis focuses on two observables: the transmission coefficient, which quantifies the fraction of energy transmitted across the interface, and additional entanglement entropy, which captures the interface’s contribution to quantum correlations. In bottom-up gravitational models, the transmission coefficient and entanglement entropy can be independently tuned, highlighting their general independence. In top-down constructions of type IIB string theory, the thesis focuses on the transmission coefficient, which is analyzed in both weak and strong coupling regimes: perturbatively in field theory, and non-perturbatively via the AdS/CFT correspondence. Both supersymmetric and non-supersymmetric orbifold theories are studied, revealing that supersymmetry protects not only thermodynamic quantities but also transport data from dependence on the interaction coupling.