First Stars - How big - Now Black Holes?

[Billy T]

First star-forming gas clouds were much denser. (Early Universe was smaller and prior to stellar fusion also had more hydrogen.) Did not most first generation stars leave Black Holes behind when the rapidly completed their life cycle? How much did the universe expanded while the first stars ran their life cycle and typically formed a pair of gravitationaly bound black holes? Did the typical star pair of the second generation also leave a pair of black holes behind when it died? How many generations before the typical star did not leave a black hole behind? How does the number of these early-generation stellar-core black holes compare with the total number of currently luminious stars? Are there enough black holes to account for "dark matter"? I.e. what fraction of the matter that "condensed" from Big Bang energy is now in black holes?

 

[Labguy]

First star-forming gas clouds were much denser. (Early Universe was smaller and prior to stellar fusion also had more hydrogen.) Did not most first generation stars leave Black Holes behind when the rapidly completed their life cycle? How much did the universe expanded while the first stars ran their life cycle and typically formed a pair of gravitationaly bound black holes? Did the typical star pair of the second generation also leave a pair of black holes behind when it died? How many generations before the typical star did not leave a black hole behind? How does the number of these early-generation stellar-core black holes compare with the total number of currently luminious stars? Are there enough black holes to account for "dark matter"? I.e. what fraction of the matter that "condensed" from Big Bang energy is now in black holes?

A lot of different questions, but all actually tied into one subject of "first stars". Good question(s) too..

I think that a review of the following sites would probably answer all questions at least to some degree. I think that I posted at least one of these before on another thread, but they are all related.

http://www.mpia-hd.mpg.de/GALAXIES/CADIS/irsee2003/PROCEEDINGS/Straka.pdf

http://citebase.eprints.org/cgi-bin/fulltext?format=application/pdf&identifier=oai%3AarXiv.org%3Aastro-ph%2F0405565

http://www.solstation.com/x-objects/first.htm

http://adsabs.harvard.edu/cgi-bin/n...J...567..532H&db_key=AST&high=3cc290f1be15543

http://www.astronomy.com/asy/default.aspx?c=a&id=2968

Let me know if there is still a specific question left...

EDIT: This one is short but has good info:
http://relativity.livingreviews.org/Articles/lrr-2003-2/node14.html

 

[hellfire]

A time ago I read a paper about black hole remnants of population III stars with Joseph Silk as coauthor, but now I was unable to find the reference again. If I recall correctly, it was postulated that most of these black holes merged hierarchically to form the supermassive black holes in the present galaxies. (I don't know whether this is the accepted view; for me it was new and I found it very interesting).

[Edit] I found the reference:
Massive black hole remnants of the first stars I: abundance in present-day galactic haloes
http://arxiv.org/astro-ph/0307171

 

[Billy T]

A lot of different questions, but all actually tied into one subject of "first stars". Good question(s) too..
http://www.solstation.com/x-objects/first.htm
EDIT: This one is short but has good info:
http://relativity.livingreviews.org/Articles/lrr-2003-2/node14.html

Thanks for ref. I looked at them all. Have saved the two best here. Your first was usless for me.

I now understand the importance of "metals" - the presence of bound electrons makes for both rapid radiation and absorption of photons, probably harse UV /soft X-rays. This permits some of the thermal energy to leave (cool) metal containing gas clouds and should also make for greater temperature uniformity. Thus, smaller post generation III stars can form as the gas is less hot and does not require so much to self gravitate / collapse.

I would not however expect uniform density within the gas cloud or for it increase steadly towards a single interior point. Thus I expect at least two regions within the cloud will eat up most of the others and form a pair of stars. The references you gave seem to be describing isolated stars. Perhaps the pairs are so far apart that they do not interact much in the evolution of each; however if all the original angular momentun must be preserved in one star - it seem to me that it could not collapse and heat to fusion temperatures. Also it seems at least poossible the gas cloud could have many condensation centers built on many very small black holes - see next paragraph.

What happened to magnetic monoploes that should have formed? Is my idea that they did, an N one being attracted to an S one and them fusing to form a micro black hole crazy? I have read that one alone might be come a BH because they are so much heavier than protons (10^15 to 10^22 times heaver as I recall reading.) If this is possible, could not these micro BHs pay an important role in condensing gas to start a star up? Nonthing about this in your references. If they do but "evaporate" does this not provide radiation to keep thing ionized (no molecular hydrogen cooling etc?) Would the extremely red shifted remanents of this radiation be seen to day? (like the cosmic background 4 degree radiation) What temperature should it have?

Any idea why the dark matter is thought to separate from baryon/ electron matter? Does not make sense to me. - gravity is gravity is it not? The more I read, the less I know.

Thanks - what do you think of these concerns?

 

[Labguy]

Thanks for ref. I looked at them all. Have saved the two best here. Your first was usless for me.

Pretty charts, though..

I now understand the importance of "metals" - the presence of bound electrons makes for both rapid radiation and absorption of photons, probably harse UV /soft X-rays. This permits some of the thermal energy to leave (cool) metal containing gas clouds and should also make for greater temperature uniformity. Thus, smaller post generation III stars can form as the gas is less hot and does not require so much to self gravitate / collapse.

I can't disagree with any of this part. Not that I know, I'm just not aware of any info to the contrary.

I would not however expect uniform density within the gas cloud or for it increase steadly towards a single interior point. Thus I expect at least two regions within the cloud will eat up most of the others and form a pair of stars. The references you gave seem to be describing isolated stars. Perhaps the pairs are so far apart that they do not interact much in the evolution of each;

For smaller-than-galactic scales I think that you, and some of S.E. Woosley's papers, are correct in this and that large clouds that can retain their angular momentum do, in fact, "fracture into two stars and the pair cannot be separated by ous instruments. This is exactly what Woosley is assuming for the Pistol star that I posted somewhere in the last day or so.

however if all the original angular momentun must be preserved in one star - it seem to me that it could not collapse and heat to fusion temperatures. Also it seems at least poossible the gas cloud could have many condensation centers built on many very small black holes - see next paragraph.

The angular momentum doesn't need to be preserved, and probably can't. See:

http://arxiv.org/PS_cache/astro-ph/pdf/0108/0108070.pdf

where part (pg.2) states that:

Numerical simulations of mergers, with (Mihos & Hernquist 1996)
and without (Hernquist & Mihos 1995) the effects of star formation, show that
gravitational torques cause the gas lose a large fraction of its angular momentum,
up to 99%, in one or two local dynamical times. The gas in these simulations develops
strong inflows and accumulates in the center. Any non-axisymmetric structures, such
as a temporary bar, would speed up the process.

That's a pretty good paper and also points out (pg. 2 also):

In order to prevent the formation of stars, small-scale density perturbations should
be effectively erased or damped. One way to achieve this is to keep the gas hot, with
the thermal speed comparable to the gravitational free-fall velocity; another is to have
an almost relativistic equation of state, where information is again transmitted faster
than the perturbations grow. The latter criterion is satisfied in objects dominated by
radiation pressure and by isotropic (well-tangled) magnetic field.

And, on pg. 5:

a frozen uniform magnetic field is important for
removing cloud’s angular momentum via “magnetic braking” on roughly a dynamical
time of the ambient medium (McKee et al. 1993).

Page 3 also starts the effect of magnetic fields. It's only 6 pages but a good one, I think.

What happened to magnetic monoploes that should have formed? Is my idea that they did, an N one being attracted to an S one and them fusing to form a micro black hole crazy? I have read that one alone might be come a BH because they are so much heavier than protons (10^15 to 10^22 times heaver as I recall reading.) If this is possible, could not these micro BHs pay an important role in condensing gas to start a star up? Nonthing about this in your references. If they do but "evaporate" does this not provide radiation to keep thing ionized (no molecular hydrogen cooling etc?) Would the extremely red shifted remanents of this radiation be seen to day? (like the cosmic background 4 degree radiation) What temperature should it have?

As far as I know, magnetic monoploes can be predicted but have never been detected, Haven't read enough on that to comment. As far as the micro black holes, I'm only aware of those that could have been caused at the BB but would be too short-lived and too small to effect Population III and galactic BH formation significantly. As far as the (2.73K) IRB, the role of massive stars/black holes is discussed at(excellent paper):

http://citebase.eprints.org/cgi-bin/fulltext?format=application/pdf&identifier=oai%3AarXiv.org%3Aastro-ph%2F0308407

Any idea why the dark matter is thought to separate from baryon/ electron matter? Does not make sense to me. - gravity is gravity is it not? The more I read, the less I know.

All I can say is that so little is known (yet) about dark matter that I wouldn't know why it would be affected by gravity any differently. In fact, gravitational effects were how it was first discovered!

 

[hellfire]

Any idea why the dark matter is thought to separate from baryon/ electron matter? Does not make sense to me. - gravity is gravity is it not? The more I read, the less I know.

They sepparate because ordinary barionic matter collapses due to electromagnetic interactions which lead to loss of energy. Non-barionic matter interacts only gravitationally.

 

[Billy T]

Pretty charts, though..

yes pretty, but about as informative to a non professional as flowers, which are also pretty.
...

The angular momentum doesn't need to be preserved, and probably can't. See:
http://arxiv.org/PS_cache/astro-ph/pdf/0108/0108070.pdf

Only skimmmed this ref. I understand that sub galactic regions might interact, if not in actual collisions, via magnetic torques, and tend to reduce their initially larger "local eddy" angular momentum, but even still I suspect that most will still find it easier to from a pair of stars rather than one.
Before reading your ref, a "crazy idea" for shedding angular momentum occurred to me, and it seems reasonable the more I think about it.
Consider a local eddy of pre-stellar gas still cold enough to have some molecular hydrogen (or post generation III with metals) for efficient radiation. If a photon (line radiation) is emitted in the direction of spin, it will have slightly higher frequency (externally measured) than when emitted in the opposite direction. The momentum it carries away is thus slightly larger. How significant is the "breaking mechanism"?

I am going to reply to helfire's comments on my problem with the separation of dark and regular matter - please read and comment also.

 

[Billy T]

They sepparate because ordinary barionic matter collapses due to electromagnetic interactions which lead to loss of energy. Non-barionic matter interacts only gravitationally.

This explains why the regular matter is cooler, not why they separate. In one of Lab guy's references I read that it is thought that the (hotter - I assume) dark matter formed "walls" etc. If anything did so, I would think it would be the colder regular matter, but even then, why does not the dark matter congregate around the condensing regular matter? What am i missing here?

 

[hellfire]

This explains why the regular matter is cooler, not why they separate.

I think cooling it explains the sepparation. The collapse and fragmentation of gas requires energy dissipation. If matter cools, then it looses energy and the orbits will became closer. Thus, the isothermal collapse which leads to a decrease of the Jeans' mass and to a successive fragmentation of a cloud until cooling does not take place, is only possible with baryonic matter. On the contrary, a swarm of non-baryonic particles will never fragmentate into smaller parts; the orbits will be modified due to gravitational interaction, but neither collapse nor fragmentation will take place.

 

[Billy T]

I think cooling it explains the sepparation. The collapse and fragmentation of gas requires energy dissipation. If matter cools, then it looses energy and the orbits will became closer. Thus, the isothermal collapse which leads to a decrease of the Jeans' mass and to a successive fragmentation of a cloud until cooling does not take place, is only possible with baryonic matter. On the contrary, a swarm of non-baryonic particles will never fragmentate into smaller parts; the orbits will be modified due to gravitational interaction, but neither collapse nor fragmentation will take place.

But as i understand it it is the hotter dark matter that is susposed to have condensed and separated. This is what is confusing me. For example, from Lab guy's third ref (post 2) I read:

"Although dark matter is thought to be relatively segregated from ordinary baryonic matter in outer galactic halos and intergalactic space today, the two may have been mixed initially. As the dark matter condensed into a denser filamentary network, ordinary matter made of hydrogen and helium gas also was gravitationally attracted by these relative concentrations of dark matter, creating Lyman-alpha "forest" clouds of gas. At the nodes of the dark matter filaments, these gas clouds collapsed under gravitation towards of the cores of denser clumps of 100,000 to one million Solar-masses that may have measured around 30 to 100 light-years across and still consisted mostly of dark matter."

What you are explaining to me would be easy to accept if the standard theory were the other way round - I.e. if the cooling of ordinary matter permitted it to condense and then attract the dark matter to the denser aggregates of ordinary matter, but that does not seem to b what the experts are saying happened. See my confusion?

 

[hellfire]

Correct, but what you are describing happens much farther away in past. At the time before of recombination, at redshifts z > 1100, the baryons are strongly coupled to photons, which generate a radiation pressure keeping baryons from collapsing. As dark matter interacts only gravitationally, its density fluctuations may grow at that time as well as earlier. So, well, you could call this growth of fluctuations "collapse of dark matter", but note that the process is very different than in the baryonic case, as it is only driven by gravitation. After recombination, radiation and baryonic matter decouple and the baryons will fall into the gravitational potentials created by dark matter. This is the typical "collapse", which is described in the theory of gravitational instability. This infall into preexisting dark matter potentials is actually necessary in order to explain structure formation, since otherwise there would not be enough time for the baryonic fluctuations to develop after recombination.

 

[Chronos]

Billy, why are you asking these questions? You obviously know the answers to most of them. I find that annoying. hellfire, whom I hold in high regard, is trying to answer them, but, you seem more inclined to argue.

 

[Billy T]

Billy, why are you asking these questions? You obviously know the answers to most of them. I find that annoying. hellfire, whom I hold in high regard, is trying to answer them, but, you seem more inclined to argue.

It is true that I know something about black holes and early universe, but not nearly as much as several others - For example until a few days ago, I was assuming that the first generation of stars were called generation I and that generation III would be the third. Some things I "know" are not well accepted and I want to understand why (change my view if need be etc.) For example, Hawking radiation, I understand well that small BHs have a much stronger gradient just outside their event horizon and assume this helps them swallow only one member of the vacuum polarization pair (leaving the other stable in our universe - at least for a while, much longer than the uncertainty product between E and T would permit, but I have no idea how or why this gets mass out of the BH and makes it "evaporate."

I am very interested in understanding more about BHs, mainly because a pair of them are the villains in my book Dark Visitor In it I consider several non standard possible sources of BHs. Magnetic monopoles being my favorite. They are very heavy, should have been produced in great quantity, but not many seem to be around now - Only evidence of them is the once observed current step in a superconducting ring that did correspond with a single monopole passing thru the ring.

One of my "off beat" theories (I have several - see thread "What Price Free Will" and "Time Does NOT Exist - Math Proof") is that the early universe was not at all like it is thought to be. There was recently some news to this effect also - something to do with there being too many already well formed galaxys, if memory serves.

I think that the magnetic monopoles did form as theory predicts they should have and and unlike the neutral matter (not yet ionized by starlight) they have a long range means of mutual attraction and formed many micro black holes, which served as the seeds for stars formation. I.e. micro BHs are a local gravitational center that is able to collect molecules still too warm to mutually condense into a micro drop of hydrogen as a seed for others to adhere to.

I am not so well informed as others here - so I ask leading questions, trying not to look too foolish by coming right out with some of my "crazy ideas." (that would get them immediately dismissed and me the "crackpot" label I may well deserve, for some of them.) I want to get others to think about things related to BHs. I have succeeded with Space Tiger - he is writing a paper as direct result of some of my questions. Perhaps I will, with my questions provoke the same in Hellfire (or you?) In any case, I am sorry if I annoyed you, but I don't think I am doing anything wrong - perhaps some good, if I induced some guy half my age to publish or even only rethink what he/she "knows." - That is the best thing an old cogger like me can do. - I am too lazy to publish myself any more and not interested in fame, career advancements, or even money with my book, which you can read for free. etc.

PS to SpaceTiger, if you are reading: The more I think about it, the stronger my view that the rate of "vacuum polarization" inside the Earth is OOM lower than in vacuum - The Casimer effect should be strong when the "space between the plates" is essentially zero. I would even accept that there is no vacuum polarization inside "solid" matter. If there is, would it not interfere with the pairing of electrons that permits superconductivity to exist?

 

[SpaceTiger]

I want to get others to think about things related to BHs. I have succeeded with Space Tiger - he is writing a paper as direct result of some of my questions.

That's probably not going to happen, as my studies seem to be indicating that the question I had been pondering is moot. I'm going to keep it in the back of my mind, though. I'll post my work when I'm sure it is or isn't publishable.

PS to SpaceTiger, if you are reading: The more I think about it, the stronger my view that the rate of "vacuum polarization" inside the Earth is OOM lower than in vacuum - The Casimer effect should be strong when the "space between the plates" is essentially zero. I would even accept that there is no vacuum polarization inside "solid" matter. If there is, would it not interfere with the pairing of electrons that permits superconductivity to exist?

I'm not an expert on vacuum polarization, but I'm not sure you understand the magnitude of difference required here. If the 1 kg black hole entered conditions even vaguely resembling a vacuum, the decay would occur in $$10^{-16}$$ seconds. Given that there is a lot of empty space inside of a solid lattice (neutral and otherwise), there's no reason to think that the BH would survive for very long. The question is still somewhat open for much larger mass BHs (that is, I'm willing to accept that the Hawking decay limit can be prolonged a little bit), but not for 1 kg.

 

[Billy T]

...I'm not an expert on vacuum polarization, but I'm not sure you understand the magnitude of difference required here. If the 1 kg black hole entered conditions even vaguely resembling a vacuum, the decay would occur in $$10^{-16}$$ seconds. Given that there is a lot of empty space inside of a solid lattice (neutral and otherwise), there's no reason to think that the BH would survive for very long. ...

Yes - I have not tried to do the numbers but eating up 1Kg in 10^-16 sec in 0.5 Mev bites (each the rest mass of the surviving member of the vacuum polarization pair) is a tremendous production and capture rate of Vac. Polarization pairs on /near the tiny surface of the event horizon.

I am in no position to argue with Hawking and the few others who can follow him, but as I don't even have the faintest idea how the mass gets out of the black hole to reduce its mass by even 0.5Mev for one swallowed electron, I keep holding my endorsement of the "evaporation" of BHs back - just silly but I never was big on accepting proclamations by small groups when what they are saying just does not seem to fit in with other things I "know." At least I want to hold out for the possibility that inside admittedly very empty "solids" there may be zero production of vacuum polarization pairs. I am also troubled by fact that when the BH swallows an electron, how does it know wheather or not it was a member of a pair. If yes, then lose 0.5Mev of mass, If no, don't lose any mass, instead gain 0.5Mev? That seems silly to me - how is the BH hole so smart?

If there were such horrendous production inside a super conductor, why would some of the recently born positrons not annihilate with one member of the "exchange energy" electrons that can not scatter off phonons? Seem to me that a lot of newly minted positrons inside a super conductor would also in much less that 10^-16 sec have it a normal conductor - after all the total mass of the superconduction electrons is probably less that your one kg of the BH. Further more, the force attracting the positron to the the nearest electron of the super conducting pair is electrical, much stronger than gravity.

I guess I am just too stubborn or worried too much about other implications to swallow things on the bases of authority. Perhaps until you know more about why this is nonsense, we should just agree to disagree on the rate of vacuum polarization inside solids (your "a few OOM different at most" vs my "may not even occur")

 

[SpaceTiger]

I guess I am just too stubborn or worried too much about other implications to swallow things on the bases of authority. Perhaps until you know more about why this is nonsense, we should just agree to disagree on the rate of vacuum polarization inside solids (your "a few OOM different at most" vs my "may not even occur")

Or perhaps you should do the research yourself. Why are you relying on me for this? You seem to have a pretty good grasp of the subject. My intuition (and current theory) tells me that it's not going to work, so it's not really worth it for me to spend the time doing more research. If yours tells you otherwise, then the ball's in your court.

 

[Chronos]

I just wished to comment on tiny black holes in general. The cosmic background gamma ray flux places severe constraints on their numbers [they cannot exist in large numbers].

 

[ray b]

resent findings of metal rich quazars and stars
point to a flaw in the total H with a small He post big bang univerce
it was far lumpier far earlyer then "they thought"
maybe every sized lumps very shortly post bigbang will be proved
sure looks to be heading that way from the newest data

 

[Billy T]

I just wished to comment on tiny black holes in general. The cosmic background gamma ray flux places severe constraints on their numbers [they cannot exist in large numbers].

Can you amplify? I prefer brief explanations as to how gamma rays imply this, but ref is OK.

Small Black Holes, even if more numerious that the currently active stars (as I think they may be.), would rarely even slightly (much less that 1 degree) deflect a gamma ray. Their capture cross section must be an extremely small fraction of the night sky.

I especially doubt gamma rays rule out many small BHs since we are not even sure what makes them. I don't beleve it, but I could agrue that the highest energy gamma rays are the result of "gravity assists" scatterings off of these numerious small black holes. - Seem to be as good as any other explanation I have read.

Again, please justify your claim.

 

[Billy T]

resent findings of metal rich quazars and stars
point to a flaw in the total H with a small He post big bang univerce
it was far lumpier far earlyer then "they thought"
maybe every sized lumps very shortly post bigbang will be proved
sure looks to be heading that way from the newest data

Thanks for the details - I think this was what I read recently and referred to.

 

[Billy T]

Or perhaps you should do the research yourself. Why are you relying on me for this? You seem to have a pretty good grasp of the subject. My intuition (and current theory) tells me that it's not going to work, so it's not really worth it for me to spend the time doing more research. If yours tells you otherwise, then the ball's in your court.

Your right. Position well taken. We all must decide what to do with our remaining time. - What we enjoy doing is high on my list. - Never did like writing papers. I was glad much of my work was classified and could not. I like to discuss ideas, teach a little, and provoke a lot (in the good sense as I have with you.) Unless someone else picks up this ball - it is lost - I don't have the interest in slaming it back with research or publication. Too old and too lazy. Enjoyed our exchange.

 

[RoboSapien]

Try answerin that preRoboSapiens.

I now understand the importance of "metals" - the presence of bound electrons makes for both rapid radiation and absorption of photons, probably harse UV /soft X-rays. This permits some of the thermal energy to leave (cool) metal containing gas clouds and should also make for greater temperature uniformity. Thus, smaller post generation III stars can form as the gas is less hot and does not require so much to self gravitate / collapse.

Ok Mr. Questioniar. I have a question for your above comments.

What will happen to a star that is the size of most massive stars in the Universe and is made up completely out of pure naturally occurring URANIUM ?

What will happen to that star in the end ? or will it ever become a star in the first place even though humans do extract lot of energy out of the element ?

 

[Billy T]

...What will happen to a star that is the size of most massive stars in the Universe and is made up completely out of pure naturally occurring URANIUM? What will happen to that star in the end ? or will it ever become a star in the first place even though humans do extract lot of energy out of the element ?

Not sure I completely understand your question/point but can say a few things I think true and are definitely related to you inquiry, if not right on target:

Does not matter significantly (or at all if we are considering massive collections of matter) what element is making up the large mass so long as the atomic number is greater than iron. Fact that some like Uranium can be split into two (or more) parts in the weak gravity field of Earth does not imply they would do so in the self gravitating mass you are talking about. They will do just the opposite - fall together and form a black hole. However, you will get a lot more energy released than by splitting Uranium from this gravitational collapse to a single point than by merely splitting uranium.

I have been warned, today, about mentioning my book (which you can read for free and which is motivated by my concern that the western world is now beginning process of losing scientific leadership as it has basically already lost technological leadership.) Book is trying to recruit bright student now planning to make more money as corporate lawyers, etc. into science fields by telling a possible cosmic disaster story as vehicle to teach a lot of science to people not currently interested in science. Appendix 3 of that book is a simple calculation (not even calculus required) showing that even a single proton falling into the point singularity gains very large amount of energy (read that as infinite) from the gravitational field. IMHO, it would be appropriated to mention it here. Note that the calculation is too simple, as the physics is very complex, not the classical physics assumed in appendix 3. I do not name book now (publicly) as I am still waiting for the response to my reply to the "warning." - send me PM and I will tell more, including how to read for free.

 

[SpaceTiger]

Can you amplify? I prefer brief explanations as to how gamma rays imply this, but ref is OK.

Small Black Holes, even if more numerious that the currently active stars (as I think they may be.), would rarely even slightly (much less that 1 degree) deflect a gamma ray. Their capture cross section must be an extremely small fraction of the night sky.

I think it's in reference to the Hawking radiation. Tiny black holes would be emitting a lot of it, so we'd see it in the gamma-ray background. If the Hawking radiation turned out to be miscalculated, this limit would of course not apply.

 

[Chronos]

Can you amplify? I prefer brief explanations as to how gamma rays imply this, but ref is OK.

Small Black Holes, even if more numerious that the currently active stars (as I think they may be.), would rarely even slightly (much less that 1 degree) deflect a gamma ray. Their capture cross section must be an extremely small fraction of the night sky.

I especially doubt gamma rays rule out many small BHs since we are not even sure what makes them. I don't beleve it, but I could agrue that the highest energy gamma rays are the result of "gravity assists" scatterings off of these numerious small black holes. - Seem to be as good as any other explanation I have read.

Again, please justify your claim.

Primordial black holes can be much smaller than stellar remnant black holes. The Hawking radiation temperature of a black hole is inversely proportionate to its mass. Stellar mass black holes barely radiate - only a fraction above absolute zero. Small black holes, however, are extremely hot. A primordial black hole large enough to last the current age of the universe - about 10^12 kg - would radiate at a temperature of around 100 billion K emitting high energy gamma rays. If black holes of this size, or smaller, were plentiful, the gamma background radiation would look much different than it does.

 

[Billy T]

Primordial black holes can be much smaller than stellar remnant black holes. The Hawking radiation temperature of a black hole is inversely proportionate to its mass. Stellar mass black holes barely radiate - only a fraction above absolute zero. Small black holes, however, are extremely hot. A primordial black hole large enough to last the current age of the universe - about 10^12 kg - would radiate at a temperature of around 100 billion K emitting high energy gamma rays. If black holes of this size, or smaller, were plentiful, the gamma background radiation would look much different than it does.

Thanks (and to SpaceTiger also). Your point is clear to me now; And as I have said to SpaceTiger several times, very probably correct.

I have tried a few years ago to follow some of the math on this in Rev.Mod. Phys. (Section B as I recall) without much real understanding. I remain troubled by how the mass gets out of the "evaporating BH".

(1)If it by the entropy related very high temperature, I say to myself that gamma rays etc. must come from some hot real surface and they are just EM radiation, like light that can't get out.
(2)If, however, the mass loss is due to the capture of one (only) member of a vacuum polarization pair, in contrast to the capture of an identical particle that has long existed in our universe, my problem is how does the BH hole know what to do (a or b)?
(a)If the captured particle is for example an electron of a vacuum polarization pair, then BH mass drops by 0.5Mev, but
(b) if the unlucky electron has been around for years, BH mass increases by 0.5Mev.

I think all electrons are identical, they don't come with tags that say "I am half of a VP pair", so how is the BH to "know" the history of the electron it has just swallowed?

Hope you can see my troubles - I just am very uncomfortable with this complex theory, the math of which I have not been able to directly follow. Sometimes someone who is not very well versed can ask simple questions better than one who is. That is what I am trying to do. Can you shed any light (or mass ) on this? Thanks in advance.

 

[Billy T]

...A primordial black hole large enough to last the current age of the universe - about 10^12 kg ...

I DON'T WANT TO STEP IN BETWEEN A CROSS FIRE BUT:

I note an an exteme disconnect between your value for lifetime and that of SpaceTiger's. In severl posts (16 and before this thread) he has been stating that a 1kg BH lasts only 10^-16sec.

If universe is 14 billion years old and there are 3600x365.25x24 sec per year, your lifetime is 31,557,600x14x10^9sec or call it at least 3.1x1.4 x 10^17= 4 x 10^17 sec. which when compared to his 10^-16 sec is mor than 4x10^31 times longer, yet your mass is only 10^12 larger.

While on the subject of older post of this thread, what do you think of my agrument that the quantum exchange energy pairing, which makes superconductivity possible, would be rapidly destroyed if vacuum polarization did occur at anything near the rate SpaceTiger thinks it does in the "empty" space inside "solids" - Seem to me the the VP positons would often annhilate one member of the energy exchange pair and force the super conductor back to the normal state. Any view on this as a counter argument to VP, at least in inside "solids"?

 

[Labguy]

(1)If it by the entropy related very high temperature, I say to myself that gamma rays etc. must come from some hot real surface and they are just EM radiation, like light that can't get out.
(2)If, however, the mass loss is due to the capture of one (only) member of a vacuum polarization pair, in contrast to the capture of an identical particle that has long existed in our universe, my problem is how does the BH hole know what to do (a or b)?
(a)If the captured particle is for example an electron of a vacuum polarization pair, then BH mass drops by 0.5Mev, but
(b) if the unlucky electron has been around for years, BH mass increases by 0.5Mev.

I think all electrons are identical, they don't come with tags that say "I am half of a VP pair", so how is the BH to "know" the history of the electron it has just swallowed?

Chronos is correct (and SpaceTiger) about the mass-energy production of a black hole (BH) by way of Hawking radiation (HR). That is limited strictly to the "lifetimes" and energy release of a non-accreting black hole. Your example (a) and (b) above are of two different things. Of course, a black hole with other matter being accreted (your (b) above) will gain mass as long as the accretion rate exceeds the Hawking evaporation rate.

So, forget about a black hole sucking in matter of any kind and place it alone in a relatively empty region of space, at least empty enough to not draw in any nearby matter. This is where we can talk about the effects of Hawking radiation alone. So, use (a) in your post above. The energy at the event horizon is as Chronos explained. This energy will produce virtual-particle (VP) pairs and not just electrons as has been mentioned so far. The VP pair is produced by "borrowed" energy from the BH. The Heisenberg uncertainty principle allows for two things here. (1) It allows the VP pair to exist on borrowed energy for a finite, but very short, period of time, and (2) it allows the VP pair to be of any energy amount as long as, again, anything borrowed is returned. Therefore, the VP pair is not limited to just electrons and positrons being discussed so far, it can also be quarks, protons, neutrons, and certain mesons regardless of energy required to produce the pair.

So, one of the "virtial" particles falls back into the BH and the other becomes a "real" particle with real mass. If it escapes into space (sometimes both will fall back in), then the mass of whatever the escaping particle was will exactly match the mass-loss of the BH. Mass is delivered into the realm of real and the BH loses that much mass, so the first two laws of thermodynamics are still happy, nothing has been violated.

How does a small BH become so hot and evaporate so fast? (One might ask.. ). Well, the "standard" HR process just mentioned was about one, single VP pair. In a large BH idling along this migh be the case here and there around the EH. But, in a smaller BH with more energy per square^anymeasure will be producing VP pairs, of many different particle types, at a great pace. Now we have a swarm of real particles buzzing all around the EH at a very high density. Some will combine into more complex particles, but most will just escape or, to produce the intense energies mentioned, many particle-antiparticle pairs will meet and annihilate into pure energy. If the density is high enough and the particles massive enough, you will see the gamma-ray production Chronos mentioned, again, especially from small, short-lived BH's. Of course, it is actually the entire EM spectrum of photons that are produced but the gamma rays get the most attention.

EDIT: Add;
http://superstringtheory.com/blackh/blackh3.html

http://casa.colorado.edu/~ajsh/hawk.html

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html

http://library.thinkquest.org/C007571/english/advance/english.htm?tqskip1=1&tqtime=0602

http://relativity.livingreviews.org/Articles/lrr-2001-6/

http://www.physics.hmc.edu/student_projects/astro62/hawking_radiation/radiation.html

 

[Billy T]

I have not had time to visit your refs yet but will. I want to thank you for taking the time/ effort to respond so well, but there is a slight misunderstanding of why I mention (b) the capture of one long existing electron.

...Of course, a black hole with other matter being accreted (your (b) above) will gain mass as long as the accretion rate exceeds the Hawking evaporation rate. So, forget about a black hole sucking in matter of any kind and place it alone in a relatively empty region of space, at least empty enough to not draw in any nearby matter.

That was my assumption. SpaceTiger has lead me to believe that a 1kg BH would only last 10^-16 sec, being eaten away in 0.5Mev bites -that is a lot of bites even if we switch to protons/ anti protons (1Gev bites). Surely the picture does not change much if I assume that one innocent old electron is eaten before the BH "evaporates" away. I was just trying to focus your attention on fact that somehow BH knows that this electron is different from all the others that in that it causes a mass gain - not very significant in the big picture, but troublesome, at least to me, as it seems to require that this electron comes whit the tag (LOL) or that the BH "knows"
it history/origin.

The VP pair is produced by "borrowed" energy from the BH. The Heisenberg uncertainty principle allows for two things here. (1) It allows the VP pair to exist on borrowed energy for a finite, but very short, period of time, and (2) it allows the VP pair to be of any energy amount as long as, again, anything borrowed is returned.

I understand well that E and T operators do not commute under the Hamiltonian and thus the uncertainty principle applies to the product of the uncertain (errors on epistimology if you like) product and certain think VP is defined better as you do and should not be only fermions. However, this "borrowing" concept leaves me very cold - There does not need to be any BH around for VP to occur. The Casimire effect (real lab measurement) proves this as well as the fact that the vacuum polarization is well accepted theory, not requiring BHs. That is "borrowing" from BH is justified way of thinking / book keeping perhaps, but has nothing to do with the physics -the black hole is not some credit bank that will lend mass for short period. Quantum Mechanics does that just fine in the absence of BHs!

Everything you say is no doubt true in some sense, but it does not help me understand how the mass gets out when one member (only) of a VP is eaten and yet in the very rare case that an identical old particle is eaten, the BH gains mass. That is my mystery/ confusion/ reluctance to sign on board and accept what I can not understand, just because "authorities" (and a very small group at that) tell me it is so. If money were envolved, i would bet they are right, but we are talking about ideas here.

Got to go now - if need to address more and chroot has not barred me form PF, I will continue later.

thanks again and in advance if you comment on the above.

 

[SpaceTiger]

If universe is 14 billion years old and there are 3600x365.25x24 sec per year, your lifetime is 31,557,600x14x10^9sec or call it at least 3.1x1.4 x 10^17= 4 x 10^17 sec. which when compared to his 10^-16 sec is mor than 4x10^31 times longer, yet your mass is only 10^12 larger.

Actually, the discrepancy is larger (4x10^33, you made a mistake in that last step). The reason, of course, is that the evaporation time goes as M^3.