Betre, Kassahun

Assistant Professor, Physics and Astronomy


Phone: (408) 924-5210


  • PhD Physics, Stanford University, 2014
  • MSc Physics, Stanford University, 2011
  • BA Physics, Macalester College, 2007


My research interest is in background independent and relational approaches to quantum gravity. Currently, the best theory about the nature of space and time is Einstein’s General Theory of Relativity (GR). Though immensely successful, Einstein’s theory leaves some important questions unaddressed; for example, about the true nature of spacetime singularities such as the Big Bang and Black Holes. It is widely believed that a quantum version of GR, a theory of quantum gravity, will answer these questions. Formulation of quantum gravity might require finding principles more basic and fundamental than space and time on which to build a quantum theory. But space and time are the most universal and basic foundations on which physical theories are built upon — what can be more fundamental than spacetime? If we think of spacetime as representing a certain type of spatio-temporal relationship among matter-energy, then the underlying relationships themselves can be considered more fundamental than their description through the concept of a spacetime manifold. One can formulate a dynamical quantum system purely relationally without reference to a background spacetime. This is achieved using combinatorial objects such as graphs and abstract simplicial complexes. The question then becomes, how does something resembling the spacetime of GR emerge at low energies from combinatorial microscopic degrees of freedom with no geometric properties? The approach I pursue defines quantum systems relationally on graphs without any reference to a background spacetime and studies emergent geometric properties using the tools of statistical mechanics and condensed matter physics.