Editing Hawking radiation (section)

===Large extra dimensions===
The formulas from the previous section are applicable only if the laws of gravity are approximately valid all the way down to the Planck scale. In particular, for black holes with masses below the Planck mass (~{{val|e=-8|u=kg}}), they result in impossible lifetimes below the Planck time (~{{val|e=-43|u=s}}). This is normally seen as an indication that the Planck mass is the lower limit on the mass of a black hole.

In a model with [[large extra dimensions]] (10 or 11), the values of Planck constants can be radically different, and the formulas for Hawking radiation have to be modified as well. In particular, the lifetime of a micro black hole with a radius below the scale of the extra dimensions is given by equation 9 in Cheung (2002)<ref>{{cite journal|last1=Cheung|first1=Kingman|title=Black Hole Production and Large Extra Dimensions|arxiv=hep-ph/0110163|doi=10.1103/PhysRevLett.88.221602|pmid=12059412|journal=[[Physical Review Letters]]|volume=88|issue=22|page=221602|date=2002|bibcode=2002PhRvL..88v1602C|s2cid=14228817}}</ref> and equations 25 and 26 in Carr (2005).<ref>{{Cite book |last1=Carr |first1=Bernard J. |chapter=Primordial Black Holes – Recent Developments|arxiv=astro-ph/0504034|date=2005|title=Proceedings of the 22nd Texas Symposium on Relativistic Astrophysics at Stanford, Stanford California, December 13–17, 2004 |editor1=Pisin Chen |editor2=Elliott Bloom |editor3=Greg Madejski |editor4=Vahe Patrosian |volume=041213|pages=89–100|bibcode=2005tsra.conf...89C}}</ref>

: <math>\tau \sim \frac{1}{M_*} \left( \frac{M_\text{BH}}{M_*} \right)^\frac{n+3}{n+1}, </math>

where {{math|''M''<sub>∗</sub>}} is the low-energy scale, which could be as low as a few TeV, and {{mvar|n}} is the number of large extra dimensions. This formula is now consistent with black holes as light as a few TeV, with lifetimes on the order of the "new Planck time" ~{{val|e=-26|u=s}}.