Research Expertise and Interest

quantum gravity, cosmology, Theoretical Particle Physics, quantum information

Research Description

Yasunori Nomura is a professor in the Department of Physics and the Director, Berkeley Center for Theoretical Physics.  One of the most important problems in theoretical physics is to reveal the quantum theory of spacetime and gravity. This has indeed been studied for long, but it is only recently that some of the key ingredients are being understood. In particular, this has brought a new connection between quantum gravity and quantum information science through the concept of holography: the idea that quantum gravity is formulated as a theory of lower dimensional quantum systems that may not involve gravity. One of his current scientific focuses is to understand this connection better.

Yasunori Nomura has recently been developing a holographic description of spacetime beyond the conventional framework of the Anti-de Sitter (AdS)/Conformal Field Theory (CFT) correspondence. He found a way of relating the so-called tensor network descriptions of quantum states to a certain geometric flow in general spacetime. He has also advanced understanding of the long-standing black hole information problem. In particular, he proposed a consistent framework of describing black hole evaporation without a information loss, in which special dynamical properties of the black hole---maximally chaotic, fast scrambling, and universal---play a crucial role in the emergence of spacetime inside the horizon.

In the past, he developed theories of grand unification in higher dimensional spacetime and constructed the so-called holographic Higgs model, the first realistic model in which a composite Higgs particle arises as a pseudo-Nambu–Goldstone boson. He also proposed that the eternally inflating multiverse is the same thing as quantum many worlds (the quantum multiverse), which addresses the long-standing problem of probability measures in inflationary cosmology.