PIRSA:26050050 Scientific Series Quantum Gravity

DOI10.48660/26050050

Series: Quantum Gravity

Zilberman, N. (2026). The semiclassical energy outflux emerging from a collapsing shell. Perimeter Institute. https://pirsa.org/26050050

Zilberman, Noa. The semiclassical energy outflux emerging from a collapsing shell. Perimeter Institute, May. 28, 2026, https://pirsa.org/26050050 

@misc{ pirsa_PIRSA:26050050,
  doi = {10.48660/26050050},
  url = {https://pirsa.org/26050050},
  author = {Zilberman, Noa},
  keywords = {Quantum Gravity},
  language = {en},
  title = {The semiclassical energy outflux emerging from a collapsing shell},
  publisher = {Perimeter Institute},
  year = {2026},
  month = {may},
  note = {PIRSA:26050050 see, \url{https://pirsa.org}}
}

Abstract

When a compact object collapses to form a black hole, quantum field theory predicts the emission of an energy outflux to future null infinity, which later relaxes to Hawking radiation. Within the semiclassical framework, we derive a simple, closed form, analytical expression for the energy outflux emitted from a spherical thin null shell collapsing to form a black hole. In particular, this energy outflux vanishes (quadratically in r-2M) as the shell approaches the horizon. This result refutes claims that the Hawking energy outflux originates from the collapsing body, showing instead that it develops in a broad strong-field region. Additionally, this vanishing implies that semiclassical backreaction cannot prevent or significantly affect the classical process of gravitational collapse and horizon formation (as sometimes claimed). [This talk is based on the joint work arXiv:2503.00622 (PRLA 135, 021401, 2025) with Amos Ori.]

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