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bachnga
2006-Aug-31, 05:21 AM
Black holes are believed to emit radiation (via Hawking radiation) of ordinary matter (photons, electrons, neutrinos, etc.). Do they also radiated dark matter? The ratio of dark to ordinary matter emitted should depend on physical constants of dark and ordinary matter, not how much of each went into the hole. Since more ordinary matter most likely falls into a hole, would Hawking radiation be gradually creating dark matter out of ordinary matter?

Blob
2006-Aug-31, 07:59 AM
Hi,

it has been proposed by some that they also produce dark energy, however, it is thought that dark matter is not `normal matter`, and that it was created fairly early one, and led to the universes lumpiness to actually create the first black holes.

Given what we know today, it is perhaps too early to say either way.

Ken G
2006-Aug-31, 04:10 PM
Since more ordinary matter most likely falls into a hole, would Hawking radiation be gradually creating dark matter out of ordinary matter? Interesting thought, and welcome to the forum. What little I know about Hawking radiation suggests that it should indeed include dark matter, but we won't know how much until we know what dark matter is. Since dark matter is generally expected to be "cold", this means massive particles, so that should give some idea of how much of it you expect relative to electrons, photons, etc. I don't know what that comparison is. Incidentally, I would expect that a lot of what goes into black holes is dark matter-- maybe most of it. Again that comparison is beyond my ability to make offhand.

GOURDHEAD
2006-Aug-31, 05:04 PM
Hawkin radiation is hypothesized based on ordinary matter existing in virtual particle/anti-particle pairs, one member of which gets sucked inside the event horizon and the other is radiated away. Is there a conjecture that dark matter can be so constructed?

Could the non-relativistic kinetic energy of ordinary matter somehow contribute to the dark matter mass?

Squashed
2006-Sep-01, 12:32 PM
... Incidentally, I would expect that a lot of what goes into black holes is dark matter-- maybe most of it. ...

That is an interesting thought. If the universe is 90% dark matter and 10% "normal" matter ** and if the percentage composition is fairly uniform throughout the universe then the earth would "appear" to be 10 times heavier than all the mass we could detect or "see".

** - I do not know what the current best estimate is.

If the above is true then that would mean that our current calculation of gravitational strength per unit mass is incorrect because we are including the gravity of dark matter. Then since we only see "normal" matter in other celestial bodies when we apply our dark-matter-inclusive gravity values to the visible-matter-only universe we will obtain incorrect results.

antoniseb
2006-Sep-01, 12:47 PM
Do they also radiated dark matter?

Hawking Radiation hasn't been demonstrated or measured, and this question kind of falls in where General Relativity and Quantum Mechanics intersect, and is therefore weakly defined.

My guess would be that if dark matter is made of massive neutral particles that have a very small cross-section for interaction with the particles we're more familiar with that if there is Hawking Radiation, that dark matter particles should be emitted, but they will be more rare than electrons or positrons.

If dark matter is made of neutralinos (the hypothesized lightest and only stable super-symmetric particle), then you should also expect Hawking radiation to include unstable super-symmetrics, which are charged and colored, and DO interact with normal matter. We might detect these in the spray from mini-black-holes made in Brookhaven.

Ken G
2006-Sep-02, 02:51 AM
If the above is true then that would mean that our current calculation of gravitational strength per unit mass is incorrect because we are including the gravity of dark matter. Then since we only see "normal" matter in other celestial bodies when we apply our dark-matter-inclusive gravity values to the visible-matter-only universe we will obtain incorrect results.

Actually, this is not a problem, because the gravity from "normal" matter already includes the component that is "dark" (basically, the only "bright" particles are electrons, but most of the mass is protons and neutrons, i.e., dark). So what is really meant by "dark matter" is matter that is dark that comes in a different proportion to electrons than what we are normally used to. So when I mentioned dark matter in black holes, I was thinking the supermassive black holes that have eaten up part of a galaxy, where there is a fair amount of dark matter. Stellar mass black holes come from stars, and in stars there is not a significant dark matter component, by the above definition.