Spacetime in Superposition

讲演择要：
If relativistic gravitation has a quantum description, it must be meaningful to consider a spacetime metric in a genuine quantum superposition. But how might such a superposition be described, and how could observers detect it必修 I will present a new operational framework for studying “superpositions of spacetimes” via model particle detectors. After presenting the general approach, I show how it can be applied to describe a spacetime generated that is a superposition of two expanding spacetimes. I will then move on to show how black holes in two spatial dimensions can be placed in a superposition of masses and how such detectors would respond. The response exhibits signatures of quantum-gravitational effects reminiscent of Bekenstein’s seminal conjecture concerning the quantized mass spectrum of black holes in quantum gravity. I will provide further remarks concerning the meaning of the spacetime metric, and on distinguishing spacetime superpositions that are genuinely quantum-gravitational, closing with suggestions as to how these ideas might be implemented in a laboratory setting.

讲演人简介：
Robert Mann is a Professor of Physics at the University of Waterloo who specializes in black holes, particle physics, and quantum information. He has authored over 600 journal papers and 2 books, and has over 33,000 citations. Formerly President of the Canadian Association of Physicists in 2010, he has received several awards, including a Fulbright Fellowship, Outstanding Referee Awards from the American and European Physical Societies, and several awards for Teaching Excellence including a Distinguished Teacher award from the University of Waterloo and the 2019 Medal of Excellence from the Canadian Association of Physicists. In 2022 he was awarded the distinction of University Professor, the highest recognition of excellence offered at the University of Waterloo. In 2024 he was recognized as a Fellow of the Canadian Association of Physicists. He is Executive Editor in Chief of Canadian Science Publishing and Senior Editor of an upcoming Comprehensive Quantum Physics volume.