# Planck stars

1 CPT - E4 Gravité quantique
CPT - Centre de Physique Théorique - UMR 7332
Abstract : A star that collapses gravitationally can reach a further stage of its life, where quantum-gravitational pressure counteracts weight. The duration of this stage is very short in the star proper time, yielding a bounce, but extremely long seen from the outside, because of the huge gravitational time dilation. Since the onset of quantum-gravitational effects is governed by energy density ---not by size--- the star can be much larger than planckian in this phase. The object emerging at the end of the Hawking evaporation of a black hole can then be larger than planckian by a factor $(m/m_{\scriptscriptstyle P})^n$, where $m$ is the mass fallen into the hole, $m_{\scriptscriptstyle P}$ is the Planck mass, and $n$ is positive. We consider arguments for $n=1/3$ and for $n=1$. There is no causality violation or faster-than-light propagation. The existence of these objects alleviates the black-hole information paradox. More interestingly, these objects could have astrophysical and cosmological interest: they produce a detectable signal, of quantum gravitational origin, around the $10^{-14} cm$ wavelength.
Document type :
Journal articles
Domain :

https://hal.archives-ouvertes.fr/hal-00957704
Contributor : Carlo Rovelli <>
Submitted on : Monday, March 10, 2014 - 9:35:11 PM
Last modification on : Thursday, March 15, 2018 - 4:56:08 PM

### Citation

Carlo Rovelli, Francesca Vidotto. Planck stars. International Journal of Modern Physics D, World Scientific Publishing, 2014, 23 (12), pp.1442026. ⟨10.1142/S0218271814420267 ⟩. ⟨hal-00957704⟩

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