PIRSA:15030075

Video URL

https://pirsa.org/15030075

Even a tiny cosmological constant casts a long shadow

Ashtekar, A. (2015). Even a tiny cosmological constant casts a long shadow. Perimeter Institute for Theoretical Physics. https://pirsa.org/15030075

Ashtekar, Abhay. Even a tiny cosmological constant casts a long shadow. Perimeter Institute for Theoretical Physics, Mar. 19, 2015, https://pirsa.org/15030075 

          @misc{ scivideos_PIRSA:15030075,
            doi = {10.48660/15030075},
            url = {https://pirsa.org/15030075},
            author = {Ashtekar, Abhay},
            keywords = {Strong Gravity},
            language = {en},
            title = {Even a tiny cosmological constant casts a long shadow},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2015},
            month = {mar},
            note = {PIRSA:15030075 see, \url{https://scivideos.org/index.php/pirsa/15030075}}
          }

Abhay Ashtekar Pennsylvania State University

Talk numberPIRSA:15030075
DOI10.48660/15030075
Source RepositoryPIRSA
Collection
Talk Type Scientific Series
Subject

Abstract

Surprisingly, several basic questions in classical and quantum gravity, which were resolved some 40-50 years ago for zero $\Lambda$, still remain open in the $\Lambda >0$ case. In particular, for $\Lambda >0$, we still do not have a satisfactory notion of gravitational radiation or Bondi 4-momentum in exact general relativity, nor a positive energy theorem. Similarly, the standard constructions of `in' and `out' Hilbert spaces that we routinely use (e.g. in the analysis of black hole evaporation) do not extend to the $\Lambda >0$ case. In this talk I will present some illustrative examples of these quandaries and introduce a systematic approach to resolve the open issues.