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Exploring Superstrings in the Lab
ultracool writes "Physicists at Utrecht University in the Netherlands have come up with a way of observing a superstring by utilizing Bose-Einstein condensation (BEC). A one-dimensional BEC in an optical lattice is rapidly rotated, causing a quantized vortex to form. The bosonic part of the superstring consists of this vortex line. Inside the vortex, they would trap an ultracold cloud of fermionic atoms. Hopefully this will allow observation of the supersymmetry between bosons and fermions, thus providing the first experimental evidence to support superstring theory."
I almost understood a word of that.. Almost.
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ StringBuilder.html .
They're great. You can modify them and they aren't synchronized so they're fast, too. If these scientists are only just now discovering them they should try reading some newsgroups.
A more detailed explanation of http://en.wikipedia.org/wiki/Superstringssuperstri ngs.
Supersymmetry between bosons and fermions is not possible in your universe. We have seen to that.
It's the one in which Q inverts a universal constant, right?
...to refer people to more information on Bose-Einstein condensates (BEC):
BEC wikipedia page
BEC home page at Colorado
BEC at NIST
What is a BEC?
this is the first experiment that could confirm the existence or non existance of super strings. This would begin to give emperical evidence to support String Theory. up until now most work on String Theory has been unable to provide a working way to test it. this could easily change the face of theoretical physics in the labs and particle accelerators.
Any string theorists out there want to chime in?
This has direct implications for the food industry. No longer will superstring cheese have to be refrigerated, the fermionic atoms will maintain an ultracold cloud around the superstring cheese, keeping it tasty and fresh. Yum.
Even those who arrange and design shrubberies are under considerable economic stress at this period in history.
If they can demonstrate that the predictions of superstring theory hold true, and that it can actually be used to connect Quantum Physics with Relativistic Physics, we might actually be able to stop some of the bickering that goes on among Physicists today.
What does that mean for us? Well, when Newton found physical laws that worked more generally than Aristotle thought, Physics was born and we were launched into a new era of science. Einstein's Special (and then, afterward) General Relativity made what we consider the modern era possible.
Quantum Physics and Relativity have always been at odds, though. After all, what makes gravity operate at a quantum level? Superstring theory is one of several "theories of everything" that would allow us to explain the world in more general terms--and in the past, every time that has happened, society and technology has taken leaps and bounds forward.
What will happen if we find out that Superstring theory really is the theory of everything? It's liable to be as outlandishly unthought of as space travel to the people of the turn of the 20th century.
String Theory was unknown to me until I saw the awesome Nova special on it..
from the article : String theorists attempt to explain all the fundamental particles as vibrations on tiny strings on length scales of about 10-33 metres. The theory naturally includes "supersymmetry" - a symmetry that connects particles with integer spin, known as bosons, to particles with half-integer spin, which are known as fermions. The particles that carry the fundamental forces of nature, such as the photon and the gluon, are bosons, while the quarks and leptons that make up matter are fermions. Although superstring theory is the leading candidate for a theory of everything, there is no experimental evidence to date for strings or supersymmetry.
Interstellar space is "ultracold", and there are some accumulations of bosonic and fermionic atoms there. Could these superstringy conditions be found there, and observed by instruments on Earth?
--
make install -not war
It's still a char array, no matter how sophisticated MSDN tries to make it sound.
Don't you just puss the button on top of the can and the superstring sprays all over the lab?
Now, for the reason: if you know some quantum physics, think of taking two composite objects and interchanging them; fermions wavefunctions change sign under this interchange. For the composite object, its wavefunction looks like (an anti-symmetrized) product of single-particle wavefunctions. If those are fermionic and there are an odd number of them in the composite wave function, interchanging the two composite wavefunctions will produce an odd number of sign changes in the product, for an overlal sign change. If there are instead an even number of fermionic single-particle wavefunctions in the composite wavefunction, the resulting even number of sign changes under interchange produces no net sign change in the many-body wavefunction.
This is easily extended to composite objects that are a composite of both bosons and fermions.
"The bosonic part of the superstring consists of this vortex line. Inside the vortex, they would trap an ultracold cloud of fermionic atoms. Hopefully this will allow observation of the supersymmetry between bosons and fermions, thus providing the first experimental evidence to support superstring theory."
Pfft. Well, obviously.
CC Licensed Serialized Story and Podcast: Ingenioustries
And if we channel a reverse impulse through the reflector dish, the superstring will disperse the space-time anomoly. Aren't you waiting for some of this quantum research to accidentally unleash a super-mega-quantum bomb.. "safety tip - avoid trying to look under God's skirts".
meh
To use a computational analogy, they are simulating the equations of string theory using a BEC as the computer. So whatever results they get had better agree with string theory! They aren't actually testing whether these explain the world, just exploring the equations of string theory with an efficient computer -- the BEC.
Of course it's possible to see symmetry between bosoms and females--
(hears enraged Slashdotters worldwide screaming bosons and fermions)
--what? nah, I've no idea about those.
You can hold down the "B" button for continuous firing.
http://www.pbs.org/wgbh/nova/elegant/program.html
All 3 hours of it are avaliable on PBS's website.
It's amazing stuff.
The book "The Elegant Universe" by Brain Greene is what the TV Special above is based on.
Definitly worth a look at - if you enjoy the TV special, have a look around for the book... It goes into a LOT more detail.
"Who says nothing is impossible? Some people do it every day!" - Alfred E. Neuman
A liquid or solid condensate at room temp exhibiting BEC properties will be nice. I wonder if liquid helium can be made that way.
If you can flow liquid helium up your arm at room temperature, it's time to talk to your landlord ASAP.
Caveat Emptor is not a business model.
So what's the definition of a fermion or a boson, and in this specific case, of a fermionic or bosonic nucleus?
Bosons have integer spin, and fermions have half-integer (n+1/2, where n is a nonnegative integer) spin. The spins of the individual quarks in nucleons (protons and neutrons) always add up to a half-integer, so nucleons are fermions. The quarks themselves are too. The spins of the nucleons in a nucleus can add up in different ways, depending on the number of each kind (proton and neutron) present. When the spins add to become an integer, the nucleus is bosonic. When the spins add to a half-integer, the nucleus is fermionic.
If a given nucleus is fermionic, then identical nuclei of that type obey the Pauli exclusion principle. If the nucleus is bosonic, then the Pauli exclusion principle does not apply to it, and the possibility of a collection of that kind of nucleus forming a BEC exists.
"It is nice to know that the computer understands the problem. But I would like to understand it too." --Eugene Wigner
So this is very cool (literally!) science, but NOT a test of superstring theory as a way to describe fundamental particles or interactions. At best, it will provide some interesting checks of the mathematical predictions of string-like theories, but only translated into this system. You still won't know if string theory has any hope of describing real electrons, photons, gravitons, etc.
IAAP (I am a physicist), and again we have an physics article posted by someone who doesn't know the difference between reality and an analogy.
The system that these folks propose to study (quantized vorticity in a Bose-Einstein condensate) can be described with the same type of mathematics that is used in superstring theory. The proposed experiments would test the validity of the math. These experiments would say nothing about whether the math of superstring theory is a valid description of the world!
A similar situation would be the following: observing a weight on a spring would confirm the math behind simple harmonic oscillators. It would not, however, tell me anything about whether the vibrational modes of the sun obey those same equations.
Analogy != equivalence!
Good scientitst might have a good feeling, a hunch, but are ready to be disproved so they can move on, because a negative value is just as good as a positive (if not as exciting).
:)
That beleive stuff is for tooth fairies and god(s)
There's nothing Intelligent about Intelligent Design.
Though I haven't compleated it yet I'll got "The Elegant Universe. Richard Morris also wrote some good books before he died.
FalconShould there be a Law?
Frankly, I'm a little bit annoyed by the treatment of scientific theories as 'absolute truths'. It's been a while since I studied physics, but basically, it works as follows:
You have empirical evidence: things you can feel, touch, hear, smell, see, etc. Beyond that, you have NOTHING. To be more precise: speculation (theory). The best theories are simply the ones that best, or most easily explain empirical findings (what you can see, touch, smell, etc.)
So the power of say, Einstein's relativity theories is not that they're 'true', but that they are theories that offer the most simple, and/or general explanation of everything we can see, hear, feel, etc. On a scale ranging from sub-atomic to inter-galactic.
Not that I'm trying to bash the parent poster in any way. I would be thrilled if something like the String Theory would gain in strength. But why? Not because it would be 'true', but because it could offer a single, unifying explanation about an incredible number of phenomena we see, feel, hear, measure, etc. A minimal set of rules that explains how our universe works. And (between the lines) offer some hints about the true nature of our universe.
But in the end: THEORY. Because I can't feel atoms or sub-atomic particles, or know anyone that can. Nor can I touch gravity waves, or imagine the speed of light in my head. But a few (relatively, no pun intended) simple rules that explain everything I could ever see, touch, hear, smell or feel, would be really, really awesome.In this case, it doesn't matter whether the nucleus is a boson or a fermion. It matters whether the atom as a whole is. Since BECs are created at very low temperatures, it is pretty much assured that every atom has all its electrons, and, for the purposes of interactions with other atoms, acts as a single particle.
I bring this up because it is quite possible to have a fermionic atom with a bosonic nucleus. Take, for example, Nitrogen-14. The 14, or course, means it must have 14 nucleons, making the nucleus a boson. However, Nitrogen has 7 protons. Thus, an N-14 atom will have 7 electrons, for a grand total of 21 fermions. With an odd number of fermions, the atom is a fermion, as well.
And, of course, there are also atoms with fermionic nuclei that are, themselves, bosons (Hydrogen comes to mind).
But spin is a vector -- it can point in any direction in space. Thus it has a direction too (hence the plus or minus).
That answers your question, but at this point you might wonder why it is assigned either plus or minus 1/2 and not any arbitrary vector. The answer is that due to the weirdness of the spin space (that is, where the electron's spin "lives"), it can be described as a projection onto the plus and minus 1/2 spin vectors along a particular axis. You are, of course, free to choose your axis.
If you can flow liquid helium up your arm at room temperature, it's time to talk to your landlord ASAP.
The poster is probably just mistaking the instantly condensed nitrogen from the atmosphere for liquid helium. Liquid nitrogen (and oxygen the other gases in our atmosphere) runs down the plumbing of your helium container as the liquid boils off and escapes.
Having LN2 run down your arm is not very pleasant either, however. Stings like electric shock at first, and if it stops stinging you know you're in BIG trouble.
IANAP, but I am an MRI technician.
A side note: Liquid helium is very expensive to produce. The bulk of the cost of production is in harvesting the gas to compress down to liquid form. All the helium that exists on Earth is the product of eons of radioactive decay. When the liquid boils off, the escaping gas rises far above our reach. That's ironic, given that He is the second most abundant element in the universe... yet we have to pay more for it than for oil (around $10 per liter).
Buford "Mad Dog" Tannen
The defining property of a fermion and a boson is that a fermions probability amplitudes add with a minus sign and a bosons probablitly amplitudes add with a postive sign[...]
As the saying goes, I don't think those words mean what you think they do.
Fermions and bosons are only defined in the context of more-that-one-particle states. One-particle states couldn't care less. The idea is that for identical particles, a particle permutation has to be a valid symmetry of the system (after all, you can't tell them apart) - and since a permutation squared is the identity, the corresponding eigenvalues of the permutation operator can be 1 and -1, that is symmetric and antisymmetric. Now:
fermions: the total wavefunction of the system is antisymmetric under a particle permutation (P[psi] = -psi)
bosons: the total wavefunction of the system is symmetric under a particle permutation (P[psi] = psi)
Incorrect! He'll feel electromagnetic fields coursing through his body. This is a valuable experience of one of the four fundamental forces of the universe (jumping out of a fifth story building would give exposure to gravity and technically the strong force though breaking your knuckles with a visegrip is a better demonstration of that force) so it's all to the good. The actual transfer of subatomic particles will be negligiable though. A better choice for him would be putting a highly radioactive isotope in his pants.
STRING THEORY IS NOT A THEORY, IT MAKES NO PREDICTIONS
This may not be fair, but Greene struck me as kind of sleazy. Notice how he is both the narrator of the show, and also one of the people being interviewed. Also notice how he breezes past making concrete predictions.
Maybe this criticism isn't fair, and this is how all revolutionary theories look when they are young. But it just struck me that Greene was presenting this stuff as though it was allready laid in stone. He basically tells the narrative story of the triumph of string theory, going from a graduate students pet theory to... a bunch of theorists' pet theory.
String theory hasnt triumphed, isnt even in a position that it is possible for it to triumph yet. So what is Greene praising so boldly? A highly speculative area which is at this point only of interest to pure theorists, since it has (as of yet) zero predictive powers.
At one point I think the lack of evidence gets so painful that he points out that there are alot of researchers working in the field of string theory now. The number is just kind of dropped vaguely like "hundreds of researchers".
The best argument he has for its validity is that it looks promising to alot of people. After all this talk about how modern physics is so confusing and counter-intuitive he circles around and uses intuition (admittedly professional intuition)to justify why this new way of doing things is better.
STRING THEORY IS NOT A THEORY. A THEORY MAKES PREDICTIONS
String theory is just a bunch of theoretical constructs which may some day be put together into something useful.
Imagine the concept of "forces" without F=ma. "All the motion we see is actually caused by these things called forces, really. Every time something moves a force was involved."
Pretty useless, it basically is just a tautology: small things aren't electrons and quarks etc, they are actually strings. Every time you see anything it isn't what you think it is, it is really a string or group of strings which happen to behave exactly like what you think it is. Great. So... what?
Alot of people seem to be excited because of the mathematical richness of this area. I am not even nearly competent to evaluate this directly, but thinking back to basic proofs that everyone has done in highschool, if you slip up you end up proving something like "0=0". Maybe this promising mathematical complexity is purely in the math and has no physical meaning. The 21st century equivalent of epicycles.
Incorrect! He'll feel electromagnetic fields coursing through his body
Are you forgetting wave-particle duality? The electromagnetic force is transmitted by electrons, which are subatomic particles. Along with gluons and photons they are bosons, IIRC.
Quick, somebody get me a pre-schooler to explain that to me. I can't make heads or tails of it.
"...At the end of the day"..."when everyone goes home, you're stuck with yourself." RIP Layne Staley