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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.'"
I wonder if this can shed some light on the subject. It talks about modeling a universe where light naturally travels at a fixed radius rather than a straight line. Assuming the radius to be extremely large, the proposed universe would act quite similarly to ours. Assuming an extremely small radius (small as in atomic-level) and I think we may be hitting upon the door of the next dimensions.
Think of it... In a world where light traveled in a fixed radius of one meter, you would see the back of your head if nothing is in the way. And, it would seem, that your head is 6.28 meters away from you. Problem is, you wouldn't be able to see beyond that one-meter radius circle. Now, what if that radius was shrunk to the atomic level... you wouldn't be able to see beyond the circle(sphere?) that the fixed radius spans. Obviously, your eye is way too large to detect that kind of precision.
Thoughts anyone?
IWARS.
People, in general, disappoint me. Politicians even more so.
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!
The problem is that
"The result of casting elementary particles outside the inheritence hierarchy is undefined."
The Manual 4.1, chapter 7 cited in Universe(3)
-- look, cheese ahoy!
And every particle DOES have "simultaneous exact position and momentum," it's just that we aren't capable of determining both through observation. We can determine one or the other.
No, not exactly, though this is a common misconception.
Heisenberg's Uncertainty Principle has nothing to do with the act of observation. The actual uncertainty is fundamental to the quantum model. It's not that you can't measure both the position and the momentum at the same time, it's more that the particle's wave aspect cannot be constrained by both 'measurements' at the same time. Think of the particle like a water balloon on the position/momentum graph: if you compress it in one direction (measuring position) it spills out in the other (uncertain momentum).
The fun part is that you can actually use the uncertainty principle to make more accurate measurements. An experiment that was done years ago in Australia proved this. The idea is that a photon travelling here from a distant star has a very narrowly defined transverse momentum: it's heading almost directly towards us, so the uncertainty in its side-to-side momentum is directly related to how much space it takes up in the sky. (Since that defines the range of angles the photon could arrive from.) Since the transverse momentum is highly constrained, the transverse position must be highly spread out. So in theory the photon could be seen as a paper-thin pancake several miles across.
Now, from the standard double-slit experiments, you get an interference pattern as long as there is a possibility of the photon 'hitting' both slits at the same time. In this experiment, the slits were replaced with radio telescopes on train cars, on a long straight section of track. (Hence why this was done in the Australian outback.) So long as the telescopes are closer together than the uncertainty in the photon's position, you get an interference pattern. Once they're further apart than that, you revert to two seperate streams of photons.
So, you slowly move the telescopes apart, watching the star, until the interference pattern disappears. Presto, you have the 'size' of the photon, which gives the uncertainty of its transverse position. Back-calculating throug Heisenberg's inequality gives you a limit on its transverse momentum. And that gives you a good idea of the 'size' of the star in the sky, in fractions of an arc second.
This has been done, and gave answers that agreed with other observations of the stars. So the Uncertaintly Principle has, in this case, improved the accuracy of measurements.
And demonstrated that the HUP is a lot more fundamental than what you said. Particles simply do NOT have "simultaneous exact position and momentum."
-- Bryan Feir
>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
Oh my God, I'm amazed - this is the observatory I actually WORK for, and it's on SLASHDOT, my God.
Forgive me for going completely crazy replying to everyone, but this is just too cool.
OK, so long as people promise not to Slashdot the server (heh, that was dumb) for anyone who wants more information, go to the main Auger website, or for even cooler information, go to the Auger site in Argentina.
Auger is actually a very interesting project, and it's not like anything you'd ever think of - it's a 1600 km^2 array of water Cerenkov detectors (10 cubic meters of water) spaced 1.5 km apart - the picture in the article is of the flourescence detector, which is more like what you think of for a standard detector, but due to the limitations of the flourescence method of detecting cosmic rays, its duty time is only 10%, as opposed to the 100% of the surface array.
The project is proceeding along... pretty well. We've basically finished the Engineering Array, a small-scale testbed to find all of the design flaws in the initial project (and boy, did we find them) and we've detected some cosmic rays which we believe to be ~10^19 eV. We've also demonstrated the hybrid design as well (events where the flourescence detector triggers as well as the surface detector).
The black hole stuff isn't the important goal of the project - the goal is to elucidate the spectrum of cosmic rays above 10^20 eV, because we have no idea where those particles come from - all of basic physics says they can't exist. This is one of the big questions in astrophysics in recent years, up there with gamma ray bursts and odd quantum states of matter.
It's way cool. And not just because I work on it...