报告题目：Do we live on the End of the World?

报 告 人:Benjamin Muntz (University of Nottingham)

报告时间：2025年4月3号上午13:30

报告地点：物理楼W260

内容摘要：

End-of-the-World branes are codimension-one hypersurfaces that mark the ending of spacetime. Interestingly, these have been argued to be necessary ingredients in quantum gravity to ensure the absence of global symmetries. Can they also serve as braneworlds? (Spoiler: Yes.)

Motivated by the Swampland Programme and in particular the Cobordism Conjecture, we propose a scenario in which a compact region of AdS5 nucleates from nothing, with a dS4 spacetime living on its boundary. We show that it can equivalently be interpreted as an up-tunnelling from AdS5 with infinite cosmological constant, following Brown and Dahlen’s proposal for ‘nothing’. Their picture naïvely suggests that the brane has infinite negative tension. However, we show that it becomes finite and positive once we employ holographic renormalization, recovering the Bubble of Something, where the domain wall becomes a boundary of spacetime. The same holds true in any number of dimensions and, moreover, at the level of metric perturbations. This provides motivation for alternative routes of obtaining cosmology from quantum gravity or string theory using domain walls, departing from conventional vacuum approaches.

报告人简介：

Benjamin Muntz is a second year PhD student at the University of Nottingham working under the supervision of Prof. Tony Padilla and Prof. Ed Copeland. Broadly speaking, he is interested in what quantum gravity can say about problems in cosmology, and vice versa how cosmology may be used to probe quantum gravity. He did his undergraduate in theoretical physics at Imperial College London followed by the elite master’s in theoretical and mathematical physics at LMU and TUM in Munich, as well at the Max Planck Institute for Physics.