Loop Quantum Gravity with Cosmological Constant

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It is known that Einstein's General Relativity (GR) is theory to describe the gravitational physics. The theory of GR has helped us to make many tremendous progresses in understanding the fundamental aspect of space and time. The theory has been successful in describing the physics of universe, as well as making predictions for various astrophysical phenomena. However it is also well-known that the theory of GR is incomplete. It loses its capability of making predictions in the extremely strong gravitational field, e.g. inside a black hole, or at the very early stage of universe near the big bang. One of the most fundamental open questions in physics is how to complete GR in order to predict physics in an extremely strong gravitational field. The complete theory of gravity that we are searching for is called "Quantum Gravity". The theory of Quantum Gravity should play a crucial role in describing the physics inside black hole, and helping us to understand the early universe near the big bang. Eventually Quantum Gravity will lead us to a revolutionary understanding of space and time. The PI's group will also train students in STEM areas of research.This award support the development of a the theory of known as "Loop Quantum Gravity" (LQG). LQG is an approach toward Quantum Gravity featured with the background independence and non-perturbative quantization of spacetime structure. In developing the theory of LQG, the PI presented a promising new formulation of LQG with a cosmological constant. The new formulation defines finite spinfoam amplitudes of LQG. It also relates LQG to many other branches of physics and mathematics, in particular, it points out a concrete relation between LQG and String/M-Theory. The new formulation of LQG with a cosmological constant is going to be fully explored in this project, hopefully making progress towards some open issues in cosmology. The proposed work aims at (1) completing both the non-perturbative and perturbative formulation of the new model; (2) obtaining new insights and tools for LQG by exploring the relation to String/M-Theory and AdS/CFT; (3) extracting phenomenological predictions on the physics of cosmological constant. This project is expected to be an important step toward a complete formulation of LQG that could be empirically tested.