Exact Results in Supersymmetric Field Theories : A dissertation on the defect and deformed

Quantum field theories (QFTs) are the most precise descriptions of the physical reality that humanity has found. Yet exact predictions are often missing as most computations are notoriously difficult to carry out. One generally resorts to perturbation theory which immediately limits the regime of validity. The need of better computational techniques and a deeper understanding of quantum field theory is evident. The highly symmetric N=4 SYM theory offers guidance in this quest. The theory's maximal supersymmetry and conformal invariance have allowed for the development of several computational techniques, most notably the AdS/CFT correspondence, supersymmetric localization and applications of integrability. These methods provide the rarity of exact results in a fully interacting QFT and shine light on regimes inaccessible by traditional computations. The insights drawn from N=4 SYM can be extended into more general settings through deformations and modifications. Three such modifications are the β-deformation, the massive deformation N=2* and N=4 SYM with a defect. This thesis summarizes a number of exact results for these three settings through: i) a spin-chain analogy for two-point functions in the defect N=4 SYM, ii) a vacuum solution for the β-deformed defect N=4 SYM and its spin-chain interpretation of one-point functions, iii) a detailed study of the phase transitions in N=2* applying localization and iv) an adaptation of the Quantum Spectral Curve to explicit calculations of anomalous dimensions in β-deformed N=4 SYM