Blackholes In The Early Universe

[E=mc^84]

Would it not be possible for many black holes to form in the beginning stages of the universe since the universe was very dense? Can that be the cause of the so called "Dark Energy" or "Dark Matter"?

 

[sylas]

It is not simply the matter density that makes formation of small black holes possible in the early universe, but rather the massive amounts of energy.

However, whether small black holes were actually formed or not, this is not possible as an explanation for dark energy or dark matter.

Small black holes evaporate very rapidly and explosively; so they are not "dark". Larger black holes can't make up the "halos" of dark matter that exist around galaxies. And they are nothing at all to do with dark energy, which is completely different from matter, or black holes.

Felicitations -- sylas

 

[E=mc^84]

It is not simply the matter density that makes formation of small black holes possible in the early universe, but rather the massive amounts of energy.

However, whether small black holes were actually formed or not, this is not possible as an explanation for dark energy or dark matter.

Small black holes evaporate very rapidly and explosively; so they are not "dark". Larger black holes can't make up the "halos" of dark matter that exist around galaxies. And they are nothing at all to do with dark energy, which is completely different from matter, or black holes.

Felicitations -- sylas

So, then u agree that black holes are a possibility in the early universe

 

[sylas]

So, then u agree that black holes are a possibility in the early universe

Yes.

 

[Skolon]

It is not simply the matter density that makes formation of small black holes possible in the early universe, but rather the massive amounts of energy.

However, whether small black holes were actually formed or not, this is not possible as an explanation for dark energy or dark matter.

Small black holes evaporate very rapidly and explosively; so they are not "dark". Larger black holes can't make up the "halos" of dark matter that exist around galaxies. And they are nothing at all to do with dark energy, which is completely different from matter, or black holes.

Felicitations -- sylas

Hawking radiation is a proved theory? Many times it is used as a true fact. But it really is?
Sorry for my ignorance!

 

[sylas]

Hawking radiation is a proved theory? Many times it is used as a true fact. But it really is?
Sorry for my ignorance!

It's a theoretical consequence of what we think physics is like. We don't have a black hole available to test, but it would break some pretty fundamental ideas in physics if there was no Hawking radiation.

 

[bapowell]

It's possible that primordial black holes (PBH) formed out of the initial density perturbations set up by inflation. Black holes would result from regions in the universe with comparatively large overdensities (or comparatively small expansion rates). In most models, these black holes begin to form when the seed perturbation re-enters the horizon after inflation -- and so the mass of the black hole is characteristic of the size of particle horizon at that time. This gives a fairly wide range of possible black hole masses: those formed early (just after the Planck time) are just fractions of a gram, however, those formed later can be much larger ($$10^5$$ solar masses).

Light black holes (with masses less than $$10^{15}$$ grams) will have evaporated via Hawking radiation by the current epoch. However, those heavier guys may well still be around. So, finally getting to your question, I think yes, there has been some work done on determining whether primordial black holes might contribute (in part or in whole) to the dark matter density. Here are two references I fished off spires (I haven't looked them over closely, admittedly).

http://arxiv.org/abs/astro-ph/0302035"

http://arxiv.org/abs/1001.2308"

The claim that PBH's make up all the dark matter seems a little difficult to make work, since it's pretty clear that we need some form of weakly interacting dark matter to get structure formation to work right. But, perhaps they suggest a way around this in the paper...

 

[Skolon]

Is suppose that LHC will create some mini black holes. Then we will really know is Hawking radiation exist. I very hope he was right! But if he's not?

But I think we can be calm because if he is wrong the Earth stop to exist log time ago. In upper atmosphere exist much stronger collisions that LHC's. So, a lot of little BH were created in time.

 

[bapowell]

But I think we can be calm because if he is wrong the Earth stop to exist log time ago. In upper atmosphere exist much stronger collisions that LHC's. So, a lot of little BH were created in time.

Fear not Skolon. Black holes produced by the LHC will be tiny and harmless. Even if they don't evaporate, they won't eat the earth.

 

[Skolon]

Really? Why is that? Because are very little and have large speed, so it will escape from Earth gravitational attraction? Or else?

 

[bapowell]

Really? Why is that? Because are very little and have large speed, so it will escape from Earth gravitational attraction? Or else?

Yes. They are tiny. They will not wander around vacuuming up the earth. Since they have a small mass, they have a tiny event horizon. Of course, if a hapless electron meanders into the path of the BH, it will get sucked in. And yes, eventually we can expect the BH to just wander off into space. It might gorge itself on elementary particles before this happens, but nothing more significant.

 

[E=mc^84]

It's possible that primordial black holes (PBH) formed out of the initial density perturbations set up by inflation. Black holes would result from regions in the universe with comparatively large overdensities (or comparatively small expansion rates). In most models, these black holes begin to form when the seed perturbation re-enters the horizon after inflation -- and so the mass of the black hole is characteristic of the size of particle horizon at that time. This gives a fairly wide range of possible black hole masses: those formed early (just after the Planck time) are just fractions of a gram, however, those formed later can be much larger ($$10^5$$ solar masses).

Light black holes (with masses less than $$10^{15}$$ grams) will have evaporated via Hawking radiation by the current epoch. However, those heavier guys may well still be around. So, finally getting to your question, I think yes, there has been some work done on determining whether primordial black holes might contribute (in part or in whole) to the dark matter density. Here are two references I fished off spires (I haven't looked them over closely, admittedly).

http://arxiv.org/abs/astro-ph/0302035"

http://arxiv.org/abs/1001.2308"

The claim that PBH's make up all the dark matter seems a little difficult to make work, since it's pretty clear that we need some form of weakly interacting dark matter to get structure formation to work right. But, perhaps they suggest a way around this in the paper...

So, what i read so far is that we cannot really know for certain if black holes formed in the early universe until it is fully tested. But, the next approaching question would be: How would these black holes distribute themselves in the universe today if they were created in the beginning stages of the universe?

Note: I am assuming that the black holes were created in the initial stages in the formation of the universe.

 

[E=mc^84]

So, what i read so far is that we cannot really know for certain if black holes formed in the early universe until it is fully tested. But, the next approaching question would be: How would these black holes distribute themselves in the universe today if they were created in the beginning stages of the universe?

Note: I am assuming that the black holes were created in the initial stages in the formation of the universe.

Thanks for the article, it is very interesting...

 

[E=mc^84]

It's possible that primordial black holes (PBH) formed out of the initial density perturbations set up by inflation. Black holes would result from regions in the universe with comparatively large overdensities (or comparatively small expansion rates). In most models, these black holes begin to form when the seed perturbation re-enters the horizon after inflation -- and so the mass of the black hole is characteristic of the size of particle horizon at that time. This gives a fairly wide range of possible black hole masses: those formed early (just after the Planck time) are just fractions of a gram, however, those formed later can be much larger ($$10^5$$ solar masses).

Light black holes (with masses less than $$10^{15}$$ grams) will have evaporated via Hawking radiation by the current epoch. However, those heavier guys may well still be around. So, finally getting to your question, I think yes, there has been some work done on determining whether primordial black holes might contribute (in part or in whole) to the dark matter density. Here are two references I fished off spires (I haven't looked them over closely, admittedly).

http://arxiv.org/abs/astro-ph/0302035"

http://arxiv.org/abs/1001.2308"

The claim that PBH's make up all the dark matter seems a little difficult to make work, since it's pretty clear that we need some form of weakly interacting dark matter to get structure formation to work right. But, perhaps they suggest a way around this in the paper...

Thanks for the article, it is very interesting...

 

[Chalnoth]

Is suppose that LHC will create some mini black holes. Then we will really know is Hawking radiation exist. I very hope he was right! But if he's not?

Well, it's pretty darned unlikely that black holes will be produced at the LHC.

But I think we can be calm because if he is wrong the Earth stop to exist log time ago. In upper atmosphere exist much stronger collisions that LHC's. So, a lot of little BH were created in time.

Basically, if it were possible for the LHC to produce black holes, then lots of them would be produced in our atmosphere every day.

 

[E=mc^84]

Well, it's pretty darned unlikely that black holes will be produced at the LHC.


Basically, if it were possible for the LHC to produce black holes, then lots of them would be produced in our atmosphere every day.

How would these black holes distribute themselves in the universe today if they were created in the beginning stages of the universe?

Note: I am assuming that the black holes were created in the initial stages in the formation of the universe.

 

[Chalnoth]

How would these black holes distribute themselves in the universe today if they were created in the beginning stages of the universe?

Well, they would behave much like dark matter, but there's the problem that there's really no way there could be so many that they would vastly outnumber the normal matter. We should also be able to detect them evaporating, which we haven't yet.

 

[Haelfix]

Well, it's pretty darned unlikely that black holes will be produced at the LHC.


Basically, if it were possible for the LHC to produce black holes, then lots of them would be produced in our atmosphere every day.

Its not quite that simple, there are many papers on TeV scale black holes in colliders and collisions scattered around hep-ph or hep-th. It is in principle possible, particularly in the context of extra dimension models and so forth. You would see a rather spectacular display of Kaluza-Klein modes.

Whats impossible is for such objects to exist and simultaneously avoid evaporation, since its the very same semiclassical analysis that predicts their existence that also leads directly to Hawking radiation.

 

[Ich]

Whats impossible is for such objects to exist and simultaneously avoid evaporation, since its the very same semiclassical analysis that predicts their existence that also leads directly to Hawking radiation.

That's interesting.
I've been discussing with an LHC-critic (maybe you know him , O.E. Rössler, who denies the existence of Hawking radiation) two years ago, and just a few weeks ago he contacted me again.
Since my QM is rather ...limited, I'd appreciate if you could point me to some basic papers on the connection between creation and evaporation.

 

[twofish-quant]

It's a theoretical consequence of what we think physics is like. We don't have a black hole available to test, but it would break some pretty fundamental ideas in physics if there was no Hawking radiation.

In particular, if black holes didn't radiate energy, this would imply that they would have no temperature. If they had no temperature they would have no entropy. If they had no entropy then you could toss stuff into it, and the entropy of the universe would decrease. If that happened, you'd violate the second law of thermodynamics.

 

[E=mc^84]

In particular, if black holes didn't radiate energy, this would imply that they would have no temperature. If they had no temperature they would have no entropy. If they had no entropy then you could toss stuff into it, and the entropy of the universe would decrease. If that happened, you'd violate the second law of thermodynamics.

I agree:)