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Black Holes and Hidden Dimensions
Slackware Geek writes "It is being reported in the Nature Science Update that a new observitory being built in Argentina to study cosmic rays could detect extra hidden dimensions if they exist. 'Cosmic rays could find holes in Standard Model of particle physics ...If the Universe contains invisible, extra dimensions, then cosmic rays that hit the atmosphere will produce tiny black holes. These black holes should be numerous enough for the observatory to detect.'"
Nobody's talking about creating any more black holes than get created naturally. They are talking about detecting black holes that do get created naturally in our upper atmosphere.
If you actually need more explanation, go to the article.
OK,
- B
http://www.bradheintz.com/
- updated
Reply to parent: nothing. antimatter is not a very exotic thing, normal matter with reverse charge reverse spin. Once in the blackhole there is no telling whether what fell was matter or antimatter, they all behave the same (increase black hole's mass, that is, and nothing else.)
Gentlemen, you can't fight in here, this is the War Room!
This would be a nice feather in the cap of string theory, which to this point does not have any experimental observations to back it up.
One of the predictions (or you could say requirements) of string theory, is that the universe contains a total of 11 space-time dimensions, 7 of which are "curled-up" and are extremely tiny. Every time you move, you pass through the entire universe in each of these 7 dimensions, although your position in the 3 "enlarged" dimensions hardly changes. The interesting thing is that a guy predicted these extra dimensions way back in the 1910's, and was ignored for about 50 years. Experimental evidence on the side of string theory (or as they're calling it now, M-theory) would go a long way towards convincing the experimental physicists that all these theoretical physicists aren't off their rockers.
---- El diablo esta en mis pantalones! Mire, mire!
Yes they would be detected by the shower of particles produced by the (very rapid) Hawking radiation decay of the black holes. Its in the article except they didn't mention Hawking radiation by name.
As the article said higher up, the smashing of cosmic rays into ozone has been known to create such an amount of energy at such a tiny level that an extremely unstable black hole can be created for an infinitesimal period of time. This object does not have close to enough energy to suck anything into it. Even if the black hole created was a bit larger than an atom, it couldn't do more than take in a few atoms before it expends the energy it has available and "fizzle[s] out".
The article also states that it is a decently rare experience that rays with enough pent-up energy arrive that a black hole can be created.
The attempt to generate these black holes ourselves is somewhat of a different matter, but not much. CERN originally got a lot of flak for attempting to do this, since a lot of uneducated people freaked out about the thought of a black hole being created. But, that has since died down because it was so long ago and, annoyingly, the average person is kinda forgetful :).
Now, onto the good stuff. The black holes that CERN is attempting to generate are the equivalent of those that the article talks about that the PAO is trying to detect. Why it won't hurt us is due to the nature of black holes and how they are created.
A black hole requires an immense amount of energy to be created on a grand scale. That's the reason that only the largest of giant stars will become black holes when nova. The more energy it has in it while in a black hole state, the greater stability is has (though it's likely excruciatingly chaotic, and that's another branch of really fun science :). The ones that will be created will only have a small amount of energy, so little in fact that they could not possibly stay in existence for long enough to do damage. More so, with every particle that is brought into the black hole it requires a specific amount of energy expended by the black hole to drag this particle in. This is, of course, the fun part because no one's quite sure what happens to this particle. Does it disappear from our dimension? Does it come back when the black hole dissipates? There's only one way to find out, and by using harmless black holes so small they cannot do any sort of damage (if it's really damage) to more than a few nearby atoms, we are extremely safe from the attempt.
Hope you find some solace in all that :)
- DaftShadow
forma3
First of all, it's believed that these other dimensions are so-called "curled up," meaning that there is some sort of circular attribute to them. Taking this into account, I remembered viewing that website and put some ideas together:
Think of what the author said in terms of particle physics. He/She looked into a world where photons moved in a circular fashion. If the radius was big, it'd be just like our current universe. If it was small, we wouldn't be able to see much beyond our point of view.
What I'm trying to say is that photons move in the three orthonormal dimensions, and change coordinates with respect to the fourth dimension. Duh. Everyone knows that. But what if there were some other particles (Higgs boson, perhaps?) that function similarly, only on these "curled-up" dimensions? The reference to the website was made simply to introduce the reader to a circular/spherical coordinate system. My comments following the link asked the reader to reduce the radius of said coordinate system.
IWARS.
People, in general, disappoint me. Politicians even more so.
>Is this detecting the Hawking radiation from an
>evaporating hole, or is it detecting other effects?
Yes, this is essentially what happens. The decay is actually somewhat more complicated; there is an initial "balding" phase in which the black hole loses its hair, along with a "spin-down" phase... after this, there's a very quick evaporation with high sphericity. Go to http://arxiv.org and search for "black hole production"; some recent papers by Giddings have details. It was believed for a while that the cross-section is geometric, which would lead to a good chance of detecting these in the next generation of colliders if large extra dimension (LED) models are correct. A paper by Voloshin indicates, on the other hand, that the cross-section is really exponentially suppressed by the black hole action. I'm not sure this has quite been settled completely.
The basic idea behind all this, by the way, is that there may be extra dimensions which are large compared to the Planck scale (up to a millimeter in size - that's about as far as gravity has been probed!). Gravity would be a field in "the bulk", that is it propagates in all the dimensions, but the standard model fields are localized on some sort of 4-dimensional "brane." There are actually a couple of different models with large extra dimensions - one is the ADD model (Arkani-Hamed, Dimopolous, Dvali) and another is the Randall-Sundrum or "warped extra dimension" model. Searching on arxiv.org for any of these names should get you links to the papers.
The basic reason for looking into all of this is the hierarchy problem, namely that the gravitational force is far weaker than the other forces. The electroweak scale is on the order of one TeV (= trillion electron volts, where one electron volt is about 1.6*10^-19 Joules). Gravity, on the other hand, is associated with a much higher energy scale. To explain this, the ADD model proposed that maybe the fundamental Planck scale is actually on the order of a TeV, like the electroweak scale. In other words, they solve the hierarchy problem by saying there is no hierarchy. Gravity propagates in more dimensions, so that its effect in our four-dimensional part of the universe looks much weaker. The other fields are localized in such a way that this ratio doesn't take any effect for them, so we see them at the "true" Planck scale on the order of a TeV.
It just so happens that the TeV scale is what we're looking at with current colliders, which is why there's so much interest in this lately. But cosmic rays give an alternate approach. Keep in mind that these ideas are very speculative, but still worth looking into.
Matt Reece
The media and the rest of the world is convinced that Argentina is synonomous with Buenos Aires. That, and they're perfectly happy to sensationalize everything as well.
The observatory is actually in a place along the Chilean border called Malargue (you'll never find it on a map - ever) which (according to all my friends there) is a little bit worried about the goings on in BA, but life, for the most part, seems normal.
Seriously, the government overhaul is the least of the Observatory's problems - the biggest problems we have are getting things in and out of the country. International customs is horrible. Ever try to explain to someone what a photomultiplier is? Or how something that looks like a very big light bulb is worth $1000?
This article discusses your question in the "Long before the Planck scale" section; the idea is that the size of the extra dimensions brings down the "effective" 4D Planck scale from the usual 10^19 GeV to about a TeV.
Actually, there are some people working on combinatorial quantum gravity models, though I don't know enough about them to be very informative. Look up "spin networks" or "spin foams."
Matt Reece
How hawking radiation actaully occurs is something I understand but do not grok. I can't really explain from ground up, since I'm not an expert. I'll give it a try but don't quote me on this.
The whole process is lending a bit of energy from nothing, such that it won't violate conservation of energy by being strictly in limits of uncertanity part of uncertainity principle. Sometimes this energy is borrowed in form of two photons with opposite momentum, some times a particle-antiparticle pair. You have to pay back soon what you have borrowed, but sometimes the blackhole gets greedy and swallows either one of your photons or you particles. When the death calles for destruction, black hole no option but to pay back what debt it has inherited. So far, so good. Now here is the part I don't really understand (I can explain preceeding part in techincal terms and in detail if you prefer, but not this part) but accept: black hole for some reason pays the debt for the pair, not only the one it has assimilated. If it does this, the other particle, photon, whatever is free to roam the universe.
Gentlemen, you can't fight in here, this is the War Room!
The essential reason is that the "fundamental Planck scale" is ~ 1 TeV in LED (large extra dimension) theories. Gravity is a "bulk" field (propagates in all dimensions) while the standard model fields are localized, so this affects them differently. The gist of it is, if you put enough energy in a small enough region, you make a black hole. If there are more dimensions, the size of that region is bigger, so it's not as difficult to make black holes.
.8 TeV for D = 6 - 10.
Let me try to outline what's going on: I'm getting this from "Black hole production in TeV-scale gravity, and the future of high energy physics" by Steven Giddings (hep-ph/0110127 on arxiv.org). It's a nice article to start with, if you want to dig into the literature on this.
(By the way, this is using the "warped" extra dimension model but the general ones are similar.)
The Planck mass in D dimensions is M_p^(D-2) = (2 pi)^(D-4) / (4pi G_D) with G_D the gravitation constant. It turns out (M_4 / M_p)^2 = (M_p)^(D-4)V_{w}, with V_{w} the "warped volume" of the extra dimensions. (I'm not being very rigorous here; in fact this is how the volume is defined, and the ratio is given by a certain integral in terms of the warped metric.) This is essentially a sort of "Gauss law" argument, over the extra dimensions.
Now, let's consider a black hole with radius r_h much less than the geometrical scale R_c of the extra dimensions. It turns out that for a black hole of mass M, spin J, in the J = 0 limit, we have r_h = 2 [C M / M_p^(D-2) ]^[1 / (D-3)] where C is some constant in terms of D that I don't want to bother writing. The Hawking temperature looks like T_h = (D-3)/(4pi r_h). This description is valid roughly for M_p > 1.1 TeV -
Black hole cross-section was assumed to be geometrical (pi (r_h)^2), but as I mentioned in another post this is questioned (look up papers by Voloshin - but Giddings questions those), and there may be an exponential suppression. Anyhow, the important point is that, once you take all this into account, you get that the cross section sigma grows when D is larger, i.e. you don't have to put energy into as small a region if there are more dimensions.
Matt Reece
It's mainly shape of the horizon and shape of the singularity that's affected due to charge/angular momentum. That, and the stability relation - too much charge/angular momentum, and everything goes to hell in a handbasket. If I had my copy of Misner, Thorn, and Wheeler here, I could expound a bit, but...
Schwarzschild metric: mass only
Kerr metric: mass+angular momentum
Reissner-Nordstrom metric: mass+charge
Kerr-Newman(sp? on second): mass+charge+angular momentum - i.e., real black holes.
J messes with the angular dependence and structure of the horizon. Not sure what charge does - it doesn't enter into the metric in many places other than the numerator. You'll note that a != 0 causes the metric to be nonsingular at the origin...
Charged/spinning black holes are interesting, because the Schwarzschild throat/Einstein-Rosen bridge may be passable in some geometries. For a standard Schwarzschild geometry, it's not - try to pass through the center of a nonspinning noncharged black hole, and you'll die, as it's not stable.
Take a note of help from Ken Perlin. And the recent post about Tron should make him happy.
:)
Quick background info on him. He has worked on texture mapping for quite some time now. Created such things as "Perlin Noise." Here is a good example. He also got an oscar for this work.
I hope this all helps you visualize the hypercube now.
"Time is long and life is short, so begin to live while you still can." -EV
Electric field comes out of the event horizon. Actually it's more correct to say that electric field is created at the event horizon, since it doesn't make any sense to say that it propogates up out of the horizon. It is perfectly valid to say that the electric field lines have been frozen into the event horizon, and are a property of the event horizon. As charged particles cross the horizon they contribute new electric field which is measurable by the way it distorts and adds to the existing field lines.
Net charge is a property we could infer from the electric field, but the actual field emanates from the event horizon, not the unreachable singularity.
Not at all. The Argentine collaboration, while a large contributor to the project, is nowhere near the sole contributor. The largest contingent in the collaboration is (guess who) the US, and so our current guess is that if all hell breaks loose, and Argentina is no longer able to contribute one cent to the project, the US will probably shore up the Argentine portion simply because the investment is so high.
:)
That, and for those in the cosmic ray research area, this observatory is so critical. At the last ICRC in Hamburg, the rappoteur (sp?) in the "Cosmic Rays >10^19 eV - Upcoming Projects" area said that the one thing that the recent data underscored most significantly is how much Auger is needed. I couldn't agree more - the two largest current observatories, AGASA and HiRes, both have markedly contradictory data, with no clear way to resolve this difference! Previous observatories tend to somewhat agree with HiRes (Haverah Park), but that's iffy at best, as AGASA has some fundamental advantages over the HiRes design. Therefore, it seems extremely unlikely that the international collaboration will let the project suffer for any troubles that the Argentines have.
It is a little unnerving, though, because for me, personally, the most promising people that I work with down there are the Argentines (and one Frenchman to be left unnamed) - the prospect of losing them due to lack of funding is really worrying. However, it should be noted that the beauty of international collaborations and a small field of study is that you get people moving cross countries to work on a project. There's already one Argentine who just got his PhD and is headed to Colorado, so we definitely won't lose him.
It should be noted - strongly! - that the observatory still is in the construction phase. 1600 autonomous water Cerenkov detectors are difficult - and expensive - to build! We're still working out a lot of the kinks in the design, so right now a lot of the work is being done off-site, though there is PLENTY of work being done on-site as well.
The most energetic cosmic rays are 10^14 more
energetic than the largest human accelerators.
The tradeoff is "luminosity". You may only see a
few of the highest energy cosmic rays in a year,
while you want zillions of hgih energy particles
in an accelerator.
Well, from what I know about black holes, as matter passes through the event horizon, the entropy increases. This increase in the black holes entropy translates into an increase in the size of the event horizon. So, as the mass increases, so does the event horizon. At the same time, the temperature of a black hole is inversly proportional to the mass. So the temperature decreases as the mass increases. On the flip side, if the mass is small, the event horizon is small, and the temperature is extremely high. Since we are talking about a extremely small black hole, we are talking about photons being radiated at an extremely high energy in a very short time. Now I understand that the uncertainty principle allows extreme fluctuations in changes in energy as long as it is "paid back" within a short amount of time. But it seems that this extreme "Heat" is being radiated off by extremely energetic photons. In my layman analysis, it would seem that such extreme energies in our atmosphere would be detectable by several means. In lieu of this, I can understand that if there are 10 spatial dimensions, energy is being radiated in all dimensions and therefore in the three spatial dimensions we experience, we would only see a fraction of the total energy radiatated. Now for my question. It would seem likely that the radiation radiates in proportion to the spacial dimensions. If these extra spacial dimensions are soooo small, then they would have only a small fraction of the total energy radiated. Therfore, wouldn't we STILL see a phenomenal amount of energy in our atmosphere from the Black Hole Evaporation???? (Sorry for the length).
Life is like a box of chocolates. I hate Chocolates!