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Researchers Discover "Magnetic Current"
fsouto writes "Researchers have discovered a magnetic equivalent to electricity. From the article, 'The phenomenon, dubbed "magnetricity," could be used in magnetic storage or in computing. Magnetic monopoles were first predicted to exist over a century ago, as a perfect analogue to electric charges. Although there are protons and electrons with net positive and negative electric charges, there were no particles in existence which carry magnetic charges. Rather, every magnet has a "north" and "south" pole.'"
The only thing new here is the current, not the "magnetic charge" from the monopole. And it's theoretical physics ridiculously far from being used in magnetic storage or computing.
Abstract from the actual paper:
"Electrically charged particles, such as the electron, are ubiquitous. In contrast, no elementary particles with a net magnetic charge have ever been observed, despite intensive and prolonged searches (see ref. 1 for example). We pursue an alternative strategy, namely that of realizing them not as elementary but rather as emergent particles—that is, as manifestations of the correlations present in a strongly interacting many-body system. The most prominent examples of emergent quasiparticles are the ones with fractional electric charge e/3 in quantum Hall physics. Here we propose that magnetic monopoles emerge in a class of exotic magnets known collectively as spin ice: the dipole moment of the underlying electronic degrees of freedom fractionalises into monopoles. This would account for a mysterious phase transition observed experimentally in spin ice in a magnetic field, which is a liquid–gas transition of the magnetic monopoles. These monopoles can also be detected by other means, for example, in an experiment modelled after the Stanford magnetic monopole search."
If this is a discovery then why did I learn about this in my electromagnetics class I took a semester ago? And why did I have to work on problems with magnetic circuits if this phenomenom wasn't discovered yet?
Nope. Gauss's law (electricity) has some nice formula while the corresponding Gauss's law for magnetism has a big fat zero.
If magnetic monopoles were taken into account, the magnetism one will have a nontrivial div like the electricity one.
Thank you wikipedia. Now I know to ask for for christmas: A Student's Guide to Maxwell's Equations! The amazon reviews are good. Let's learn together, slashdot. div grad curl too, in case old Maxwell's a little heavy with the vector calc
I think so. It sounds more like "electron holes" in semiconductors. The spin ice contains tetrahedrons formed from ions. Because of this arrangement, adjacent ions must form a positive-negative pair, which then affects the way electrons spin and the resulting magnetic field. Bring in an external magnetic field and that runs the process in the opposite direction. That's where the storage idea comes from.
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No, they aren't. Maxwell's equations don't preclude magnetic monopoles or the movement of net magnetic 'charge' (aka 'current'). In fact it's always been a mystery why monopoles didn't appear to exist. There was no theoretical reason why they shouldn't, we have just never found a particle carrying a net magnetic charge. We still haven't exactly, just a crystal structure in which you can find discreet units of net magnetic charge, but that's effectively the same thing. And now we've seen that these units can move through a structure, so magnetic current exists.
In a way this must be a relief. Electricity and magnetism are symmetric in so many ways, it was odd that in this one way they weren't since they're ultimately aspects of the same force (electromagnetism).
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More buzzwords and concepts for Trek to abuse.
...that whizzing sound is my karma, flying out the window.
Magnet current? Like, in a transformer?
No, that's a 'spark'. Still, it might be disguised as a magnetic current.
There was also no theoretical reason for monopoles _to_ exist. If charge exists, and moving electric charges create magnetic fields, who do you _need_ magnetic charges? Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
"Discrete units of net magnetic charge" may be a quantum effect of aligned, moving electrical charges. I still see no need for monopoles.
I just tried to think about negative mass, thanks for the headache.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
There was also no theoretical reason for monopoles _to_ exist.
Well, if there is so much as one magnetic monopole in existance, it would explain the quantization of electric charge. I call that a theoretical reason for monopoles to exist.
Maxwell's equations don't preclude magnetic monopoles
False. As you find them in a standard text book, they do exactly that. Div B = 0 means no magnetic monopoles. That said, the standard equations can be easily modified to accomodate magnetic monopoles (a few books do this -- Classical Electrodynamics by Julian Schwinger might be one).
ttp://en.wikipedia.org/wiki/Magnetic_monopole#Dirac.27s_quantization
The "Gauss' Law" for magnetism (in quotes because this isn't a universally accepted name) is commonly taken to be div(B) = 0, but that's not always the case. The law can be div(B) = rho_m (Gaussian units), where rho_m is the magnetic charge density, analogous to the rho_e electric charge density in Gauss' law. In this case there is also a non-zero J_m, magnetic current.
Basically, Maxwell's equations and the rest of EM theory accept a magnetic monopole freely, but as far as we have seen, none exist in nature. Paul Dirac has shown that the existence of magnetic monopoles would explain the quantization of electric charge.
There was also no theoretical reason for monopoles _to_ exist.
I think the point the GP was making was that there was no reason that they couldn't exist...
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Okay, yes, I almost replied to myself to point out that the one equation based on the lack of the observation of magnetic monopoles would change. But none of the rest of the theory would change, and as you point out Maxwell's theory perfectly accommodates this change, so yeah, Maxwell's equations(plural) aren't "crying", except maybe with joy that now the expected symmetry has been discovered.
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No, they aren't. Maxwell's equations don't preclude magnetic monopoles or the movement of net magnetic 'charge' (aka 'current'). In fact it's always been a mystery why monopoles didn't appear to exist. There was no theoretical reason why they shouldn't, .
Yes and no. Its true that if you look at maxwells equations in the traditional form (with div and grad) the statement of no monopoles (Div B) is simply one of empirical observation: monopoles have not been seen.
However if you cast maxwells equations in differential forms it becomes intuitively obvious why there are no magnetic monopoles. electricity is a one form. Magnetism is a two form. Two forms cannot come from monopoles.
Were should have stopped 10 beers ago.
That's only an artifact of Maxwell's equations assuming there are no magnetic monopoles. Add them in, and the equations are perfectly symmetrical for electricity and magnetism, the only difference is the name of the variables and the quantities they represent are swapped. Their partial differentials are identical otherwise.
Electricity and magnetism are two aspects of the same force, electromagnetism. They are mediated by the same particle, the photon. The lack of symmetry in this one aspect is theoretically unnecessary, and philosophically kinda weird. That's not proof, of course. Demonstration of net magnetic charges is.
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The law may need to be rewritten, but as written it does say no monopoles.
Which is trivial to do, and doesn't contradict the rest of the theory, and hence they aren't "crying". The possibility of monopoles has been accepted for a very long time. It's simply the lack of experimental observation that ever caused them to be written in the first place. Re-write Maxwell's equations given the existence of 'magnetic charge', set that charge to always be zero, and you get the equations as written.
Maxwell's equations don't preclude the existence of monopoles. They are simply stated in terms that assume there aren't any based on the lack of evidence for them. His theory is fine, his equations are not "crying".
I don't understand why this is so hard to understand. Outside of the fact that you're all just being pedantic. I guess I should have said Maxwell's theory of electromagnetism.
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...that whizzing sound is my karma, flying out the window.
You've discovered the karmic equivalent to electricity!
The phenomenon, dubbed "karmicity", could be used in meta-moderation or in troll suppression. There were previously no known particles in existence which carried karmic charges. A net-positive karmic particle is known as a karmon; a net-negative particle, a moron.
LHC, eat my shorts.
I think the point the GP was making was that there was no reason that they couldn't exist...
Exactly. It isn't necessary that they exist, but there's no reason they could not exist and it makes a lot of sense for them to exist for various reasons (charge quantization and symmetry between aspects of the same force being big reasons). But we've never observed them, hence the equations as stated do not account for them. Observe one, and you can trivially modify the equations to account for the fact. The theory is pre-built to accept them. Hence they're not "crying".
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...we're 0.00317% closer to flying cars!
Table-ized A.I.
The reason you don't see Maxwell's Equations with magnetic charge in textbooks is because it's pointless to leave them in unless you're specifically looking at the problem of "how would X change if magnetic charge existed?". I happen to have a textbook that assumes magnetic charge throughout the entirety of the text (Balanis, Advanced Engineering Electromagnetics) It doesn't mean that the equations preclude it. Heck, in antenna analysis we model antennas using magnetic current/charge.
So, what's the next breakthrough? According to the Alpha Centauri tech tree I'm reading, we can now research Unified Field Theory and Nanominiaturization now that we have Monopole Magnets!
Okay, I'm replying to myself as I thought I should immediately after posting the above.
Yes, Gauss's Law of Magnetism, one of Maxwell's Equations, says the magnetic field has zero divergence, meaning there is no net magnetic charge.
That is an assumption based on the lack of experimental evidence for a monopoles.
This does not mean Maxwell's Equations preclude the existence of monopoles, because they don't. What's the difference between precluding their existence, and presuming their non-existence? Well, let's look at something that is both assumed and precluded by theory: the speed of light being different for different inertial observers, and Special Relativity.
Special Relativity assumes c is constant for all inertial observers. It also precludes the possibility of that not being true, because the entire theory is based on that assumption, and falls apart if that assumption does not hold. All the equations of special relativity contradict observer-relative speed of light. If you ever discovered a case where this was not true, you would have to scrap Relativity and re-write the theory from scratch. That's precluding.
Maxwell's Equations assume net magnetic charge is zero, but if that assumption doesn't hold, then you simply have another term in the equations and you don't need to go back to the drawing board. Gauss' Law of Magnetism simply becomes a special case where net magnetic charge is zero (though this 'special' case is the most common case). You don't need to re-write the theory of electromagnetism. These researchers are not claiming to be re-writing the theory of electromagnetism, because the theory does not preclude magnetic monopoles.
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Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful
Discussion of the existence of monopoles or true magneto current -- seriously, people -- this sentence is glaringly false. In fact, the use of magnetic charge and magneto have been integral* to electromagnetic analysis for more than 50 years now. Using the symmetric form of Maxwell's equations. The fields created by all sources and media inside an arbitrary closed surface can be analogously modeled as charge and current distributions over the surface. This is what allows you to equivalently model the open end of a driven waveguide as a rectangular patch of magneto current, an electric dipole antenna as a "cigar band" of magneto current wrapping around the feed gap. All of which, I should add, makes the equations much easier to solve. Hell if nothing else the addition of a magnetic boundary conditions can allow numeric models to converge much more quickly.
Arguing that the phenomenon discovered does not truly uncover a magnetic monopole is one thing. Arguing that there is no benefit to symmetrical equations is as silly as that there is no benefit to expressing the equations in the "bastardly" phasor vector notation when a simple set of 12 differential equations of 12 variables would suffice.
*No pun intended.
AKA negative masses would "fall" up.
Ah, like Helium balloons.
</sarcasm> <-- for the humour impaired, and those that think I might be posting from the Southern US.
What, you haven't encountered the idea before? It's been around a while. Look here.
Well, in the interest of closing the loop, these aren't totally disjoint ideas ;^)
In the standard magnetic circuit with flux and field, the analogy between a magnetic circuit and an electrial circuit is
MMF = PATHINTEGRAL (H dot dl) vs EMF = PATHINTEGRAL(E dot dl)
Without any magnetic monopoles, this path integral that represents the magnetic circuit is merely analogous to a magnetic charge making a loop in the circuit creating a potential around the loop. Although this MMF is now taught as being generated by transformer/inductor coils wrapped around the magnetic circuit using the relationship MMF = N*i, but instead in a world with magnetic monopole current (i.e., magnetic current), in principle the same MMF relationships can be used.
Interestingly with magnetic monopoles this can also be extended like "electrical" circuit element.
R = dv/di, C = dq/dv, L = dF/di, M = dF/dq, i = dq/dt, and v = dF/dt
Historicall, only Resistance ~ Reluctance was the only one of the analogs that made sense w/o magnetic monopoles.
Now that we have magnetic monopoles, the other electrical circuit elements now have possible analogs in a magnetic circuit.
So this is actually a similar idea that shouldn't be dismissed out of hand.
You just failed physics. Congratulations.
There is no such thing as negative energy (without negative mass anyway).
What you're confusing with negative energy is relative energy--an object can be said to have negative potential energy if it has less potential energy than the arbitrary zero level. This is not the same thing as negative energy (any more than being in debt is having negative dollars, or being below 0 degrees Farenheit is having negative thermal energy).
The classic illustration of magnetic field lines is to put a big bar magnet on a table and sprinkle iron filings on and around it; they will end up tracing the magnetic field lines of the bar magnet.
So say they could construct the monopole equivalent of such a bar magnet, just one big lump of North or South. If we put that on a table and sprinkled iron filings on and around it, what (if any) lines would they end up tracing? Just rays away from the monopole?
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Look no further! I've got one right here in my kitchen (driving my microwave oven).
I thought magnetic monopole was a way to play monopole during long family roadtrips.
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Why not link directly to arXiv in all scientific posts? Maybe a divulgative link AND a link to the paper in the arXiv. I am crazy?
Would they though? Assume a negative mass which still has a positive volume. If you use the (probably way oversimplified) model of positive mass objects acting like a lead ball on a rubber sheet in space you'd wind up with negative mass objects pinching it and pulling it upwards.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
Negative mass is easy.
You take one 1 kg of regular mass and place on a scale. The scale reads out 1 kg.
Now you place 1 kg of anti matter on the scale on top of the regular matter. Now there's no weight on the scale.
There's also no scale any more, but that's irrelevant for this thought experiment.
or being below 0 degrees Farenheit is having negative thermal energy
And you just failed physics by confusing temperature and thermal energy. Congratulations!
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There was also no theoretical reason for monopoles _to_ exist. If charge exists, and moving electric charges create magnetic fields, who do you _need_ magnetic charges? Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
"Discrete units of net magnetic charge" may be a quantum effect of aligned, moving electrical charges. I still see no need for monopoles.
If you have an analysis of Maxwell that explains the quantization of electrical charge without requiring the magnetic equivalent, you should show it to people. Dirac couldn't do it, so if you have it'd be well received. Not only did Dirac's equations require them, he predicted the magnetic charge quanta to be 68.5 times the electrical charge quanta. Proving Dirac wrong would have enormous consequences, since the 1983 theory of electroweak unification required them to exist and have the predicted charge magnitude, and the W+, W- and Z(0) intermediate vector bosons it predicted (based on the theory that required monopoles) have been detected. Not only that, they have precisely the charge magnitude predicted by the theory based on the predicted magnetic charge magnitude. And if you can show where Dirac went wrong, you can also show where t'Hooft and Polyakov went wrong, since they independently not only showed that any such unification theory required them, but also came to the same prediction of magnitude of magnetic charge as Dirac. Three independent theoretical analyses that make specific predictions which have been tested and shown to be correct would seem to be a tough nut to crack. But if you can show where these were all wrong, it'd be worth a Nobel, just as Weinberg, Salam, and Glashow shared one for the electroweak unification predictions that testing had subsequently and apparently mistakenly supported with data. In fact, if you can point to where Dirac et al. were wrong, you could save a lot of people a lot of money, since the search for the Higgs boson is based on symmetry breaking that requires the monopoles to exist and have a specific charge. If you could just point out where Dirac went wrong, say on the page at http://encyclopedia2.thefreedictionary.com/Magnetic+monopoles then we can call CERN and tell them to recalibrate the LHC because they followed Dirac's mistake when they built it. Or should they just trash it? It must really be hosed if it's based on a theory that predicts things, some of which have been detected exactly where they were supposed to be.
Oh, and while you're taking a balanced equation and unbalancing it, the answer to your other question is on that page too. An electrical charge in motion creates a closed magnetic field, so a magnetic charge in motion creates a closed electrical field. You may feel free to not see a need for it either, but by now it should be clear why you don't see these things as necessary. This latter result would seem at second look to be dismissable since it predicts an essentially perpetual motion. However, the perpetual motion machine it describes is available for examination in every electron orbiting every nucleus. This closed electrical current has been detected at a classical scale as a persistent flow such as a superconducting current, in a normal resistive metal ring. This was announced in Science magazine a week ago and mentioned in http://hardware.slashdot.org/article.pl?sid=09/10/10/1338210
Actually it is understandable that some people don;t see the "need" for monopoles any more than they see the need for scalar waves. This is because it has become common to teach the essentials of Maxwell's equations by arbitrarily ignoring some aspects. this is done by setting some of the necessary variables to zero. While this allows one to examine the isolated na
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What is a magnetic field composed of? The article says that a small magnetic field is formed around the muons. Is a magnetic field composed of particles?
And balloons filled with a negative mass equivalent of helium would sink.
Or you they rise faster?
This hurts my brain.
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Note to self: physics-based sarcasm is a bad idea.
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The density difference between the negaHelium and air would be greater than that between Helium (classic flavor) and air. Hence, the negaHelium experiences a greater buoyancy force, and should rise faster.
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A "field" in math is an object that assigns a value to every point in space. A "magnetic field" assigns a vector that has to do with the amount of force experienced on an electrically charged particle moving with a certain velocity at that point. So it's not really "composed of" anything, any more than the earth's gravitational field is composed of anything. It's just a property.
In other words, set up these two bodies, and they'd chase each other across the universe at ever increasing speeds, forever. Which would appear to violate conservation of energy.
Would it? The negative mass will also have negative kinetic energy.