Holography and the Swampland: Constraints on theories of fundamental physics from compatibility with quantum gravity

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Fundamental physics is built on the two pillars of General Relativity, our theory of gravitation, and QuantumMechanics, our theory of the sub-atomic world. The two theories are, however, incompatible in their currentform. A central problem in physics, with relevance for a spectrum of questions from black holes to dark energy,is how to unify them into a single theory of Quantum Gravity. Recently, it has been understood that a viableand productive approach to studying quantum gravity is by determining general principles which any theory ofquantum gravity must satisfy. For example, there is strong evidence that in any quantum theory of gravity,gravity must always be the weakest force (the Weak Gravity Conjecture). This approach to studying quantumgravity has been termed the Swampland program.The project is set within the Swampland program of research: its aim is to establish general principles ofquantum gravity and to determine how they constrain physical theories. We propose, however, to introduce afundamentally new approach to the topic. Specifically, our primary methodology will be to utilise the principleof gravitational holography (or AdS/CFT), which states that gravity is dual to a non-gravitational theory in oneless dimension. To this end we propose to form, for the first time, a large-scale collaboration bringing togetherexperts in the Swampland and Holography. This will open up two new pathways for progress: First, it will allowus to constrain quantum theories of gravity through constraints on the holographic quantum field theory duals.We can then bring new techniques to bear on the topic, from the bootstrap program to quantum informationtheory. Second, it will provide new tools for establishing the physics underlying the conjectured Swamplandconstraints. We will further supplement this methodology by testing the proposed quantum gravity constraintsin string theory, and by utilising the framework of the corpuscular description of gravity.The results of the research will yield a more robust, general, and microscopic understanding of the constraintsquantum gravity imposes on physical theories. They will change how we construct theories of new physics, forexample, constraining theories of cosmological inflation. They will elucidate the physics of de Sitter and AntideSitter spaces in quantum gravity, a question which is relevant for the nature of dark energy and the fate ofour universe. The role of holography will also allow us to expand the impact of our work: following the oppositedirection, we can convert constraints on quantum gravity into dual constraints on field theory, teaching us aboutaspects of non-gravitational theories and potentially forming connections to quantum information theory.