Quantum Gravity and Quantum Cosmology

Explore the fascinating intersection of quantum mechanics and cosmology in this 36-minute plenary session talk by James Hartle from the University of California, Santa Barbara, delivered at the APS April Meeting 2015. Delve into the quantum theory of the big bang, known as quantum cosmology, which combines a quantum theory of gravity with a theory of the universe's quantum state. Discover how this framework predicts probabilities for different large-scale classical spacetimes and observable phenomena, including the universe's homogeneity and isotropy, inflation, cosmic microwave background fluctuations, and galaxy distribution. Examine simple models based on semiclassical quantum gravity and the no-boundary wave function of the universe, as proposed by Hawking and collaborators. Gain insights into how Einstein's general relativity, a century after its inception, continues to have profound implications for both the very large and the very small scales of the universe.