• DOI:10.21468/SCIPOSTPHYS.10.2.041
• Corpus ID: 211044141

The Holographic Nature of Null Infinity

@article{Laddha2020TheHN,
  title={The Holographic Nature of Null Infinity},
  author={Alok Laddha and Siddharth G. Prabhu and S. Raju and Pushkal Shrivastava},
  journal={arXiv: High Energy Physics - Theory},
  year={2020}
}

• Alok Laddha, Siddharth G. Prabhu, +1 author Pushkal Shrivastava
• Published 6 February 2020
• Mathematics
• arXiv: High Energy Physics - Theory

We argue that, in a theory of quantum gravity in a four dimensional asymptotically flat spacetime, all information about massless excitations can be obtained from an infinitesimal neighbourhood of the past boundary of future null infinity and does not require observations over all of future null infinity. Moreover, all information about the state that can be obtained through observations near a cut of future null infinity can also be obtained from observations near any earlier cut although the converse is not true. We provide independent arguments for these two assertions. Similar statements hold for past null infinity. These statements have immediate implications for the information paradox since they suggest that the fine-grained von Neumann entropy of the state defined on a segment $(-\infty,u)$ of future null infinity is independent of u. This is very different from the oft-discussed Page curve that this entropy is sometimes expected to obey. We contrast our results with recent discussions of the Page curve in the context of black hole evaporation, and also discuss the relation of our results to other proposals for holography in flat space.