An Overview of Quantum Gravity Methods

A theory of everything, or a theory of quantum gravity, refers to the unification of two of the most fundamental concepts in physics: quantum mechanics and general relativity. It was inspired by quantum field theory, which unifies quantum mechanics and special relativity. This literature review is an overview of the different approaches to this theory. The initial background theory provided is used to explain the gaps that need to be filled in order to develop a theory of quantum gravity. Loop quantum gravity and string theory are explained in detail in terms of the broad concept, their limitations, and a brief comparison to each other. A more general synthesis of other approaches, including and limited to asymptotic safety, quantum field theory on curved spacetime, and supergravity is covered. The method of research involved primarily reading journal articles, textbook chapters, and lecture notes. The paper concludes that a lack of experimental data is the key reason why it has not been determined which theory, if any of them, is correct. String theory and loop quantum gravity remain the top contenders, with minor theories, like the other three, being more helpful in gaining insights in mathematics and physics.