Quantum Gravity and Cosmology

Synopsis

In this talk, I'll review how in our current best understanding of quantum gravity (known as holography), classical spacetime and Einstein's equations emerge from intrinsically quantum phenomena such as entanglement. I'll discuss recent efforts to describe cosmological physics (the physics of expanding universes with a big bang) using this approach.  I will explain that while the holographic gravity theories are naively unrealistic because they have a negative cosmological constant, generic cosmological solutions in these models have time-dependent scalar fields that can lead to realistic cosmological evolution with late time accelerated expansion. Observationally, these models can be distinguished from the Lambda-CDM model by the presence of decreasing dark energy. I present an observational study (with Chris Waddell) using supernova and BAO data that suggests such models with decreasing dark energy via a time-dependent scalar are preferred over the standard Lamdba-CDM model in a standard likelihood analysis. The talk will be broadly accessible to undergraduates,  graduate students, and faculty in all fields.