Does Hawking radiation depend of what's inside a black hole?

Question

Or is it entirely based on the existence of an event horizon?

Does the fact that black holes radiate depend on any properties of its interior?

Answer 1

No, it just depends on the volume and mass of the sphere. This is all theoretical however.

Excerpt from wikipedia

The radiation temperature is inversely proportional to the black hole's mass, so micro black holes are predicted to be larger emitters of radiation than larger black holes and should dissipate faster per their mass.

Answer 2

I need to emphasize upfront that the radiation is not coming from the interior or the matter that formed the black hole. It's coming from the horizon distorting nearby quantum fields.

Your question is intimately related to the information paradox. Let's consider a neutral, non-rotating black hole. Regardless of the particular matter and radiation that collapsed to form the black hole, the horizon will emit a thermal spectrum of radiation at temperature: $$ T= \frac{\hbar c^3}{ 8 \pi k G M }$$

This is what happens no matter the initial conditions which settled to form the neutral, non rotating black hole.

Taken to the extreme, this is in tension with quantum mechanics. Consider a basic particle scattering experiment. N particles go in, M particles come out. While the outcome of the experiment is not determined by quantum mechanics, the results follow certain probabilistic patterns, correlations, and rules. Furthermore, if you don't know the identity of the N incoming particles, you can deduce from the M outgoing particles the probability for what the original N incoming particles were. Information is not lost.

Black holes seemingly mess with this. In that case an enormous number of particles go in, ~10^60 for a solar mass black hole. These ~10^60 particle form an event horizon which then radiates at a thermal spectrum of M photons until the black hole disappears.

The matter which formed the black hole contained an enormous amount of info. Where did it go? Was it transferred out through the radiation? That's hard to justify because thermal radiation contains almost no information. It's very high entropy. Imagine trying to send a copy of the entire 30+ years of the internet through a radio signal of pure static. Sounds impossible right? Copying the info in a black hole through thermal radiation is much, much more difficult, exponentially so.

You may counter that normal quantum systems emit thermal radiation all the time. Heat up a piece of metal and it'll thermally radiate. Yes, but the metal doesn't disappear behind a shrinking event horizon. So it's theoretically possible to reconstruct the insanely complicated quantum interactions that caused the red hot metal to emit radiation.

Now consider the contrast.

1)In quantum mechanics, N particles scatter and produce M particles. The M outgoing particles are probabilistically correlated to the N incoming particles.

2)With general relativity, N particles form a black hole which thermally radiates away as M photons. The thermal radiation doesn't seem to contain any information about the original N particles.

What's going on? Where is the information about what formed the black hole? Good question. I don't know.