Are elementary particles ultimate fate of black holes?

From the “no hair theorem” we know that black holes have only 3 characteristic external observables, mass, electric charge and angular momentum (except the possible exceptions in the higher dimensional theories). These make them very similar to elementary particles. One question naively comes to mind. Is it possible that elementary particles are ultimate nuggets of the final stages of black holes after emitting all the Hawking radiation it could?

Yes, black holes are special kinds of elementary particles. That’s how they have to be represented in every consistent quantum theory of gravity. This representation of a black hole becomes especially useful and important for small black holes – whose mass is not much larger than the Planck mass.

And indeed, a black hole evaporates, which is just a form of a decay of a heavy elementary particle, and when it becomes very light, at the end of the Hawking evaporation process, it is literally indistinguishable from a heavy elementary particle that ultimately decays into a few stable elementary particles.

However, a difference that you seem to neglect is that black holes actually carry a large entropy

S = \frac{A}{4A_0} k_B

where A is the area of the black hole’s event horizon and ( A_0 ) is the Planck area ( A_0=\hbar G / c^3 ). The constant ( k_B ) is Boltzmann’s constant. This means that there actually exists a huge number of microstates

N = \exp(S / k_B)

and a single black hole, with a fixed value of mass, charges, and spin, is just a macroscopic description of the ensemble of N “microstates”. In reality, the black hole carries a huge information – the world distinguishes which of the N microstates is actually present.

It is these “microstates” that are really analogous to types of elementary particles. But the number of particle species that macroscopically look like the black hole of given mass, charges, and spin is not one: instead, it is huge, approximately N.

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— answered Feb 27 ’11 at 16:45

— Lubos Motl

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