Causality Constraints in Quantum Field Theory and Quantum Gravity

We explore the consequences of micro-causality in quantum field theory and quantum gravity. To this end, we develop methods in conformal field theories (CFT) by considering collider type experiments. Using this, we find a class of positive operators in a certain class of holographic CFTs. Positivity of these operators helps to describe the mechanism for the emergence of weakly interacting Einstein gravity description of the dual theory in anti de-Sitter spacetime. We also provide a dictionary for describing how these operators play a role in the dual bulk spacetime as shockwave states. Furthermore, we develop techniques to explore the consequences of causality in flat spacetimes by studying S-matrix consistency conditions. Using these methods, we place constraints on the higher spin spectrum of theories that include gravitational interactions