How many times can you discover something for the first time…

now, now, the title sounds strange as discovering something should imply doing it for the first time… right? Again, WRONG! 

Some years ago (maybe three) we were told in the same way that THE MAGNETIC MONOPOLE HAS BEEN DISCOVERED! Back in Romania we had jokes with “radio Erevan” usually discussing about soviet censorship and how a honest news was deformed by the censors in order to fit with the soviet doctrine… fortunately this is not the case now… now, it’s scientists that change news in order to fit to the doctrine of the funding body… so, Three years ago they discovered a magnetic monopole which was in fact not a magnetic monopole, in a free state which in fact was a atomic lattice in a natural environment which in fact was magnetic ice… now, the subject is interesting and deserves some remote analysis… While doing second quantization (you know, go to a Fourier representation, take the coefficients, impose on them commutation and anticommutation rules, introduce a Hilbert space and start playing with them in all sort of interacting environments) what you actually do is define a vacuum… and impose something called “normal ordering”. This “normal ordering” prescription tells you in principle that all the creator operators are at the left of all annihilator operators. It is only a rule but it has important effects on the value of the “vacuum energy”… Whenever no gravitational interactions are included (and spacetime is flat) you can do that. The choice is not unique but the fact that you “renormalize the vacuum” means essentially you assign to it a finite value. Beware however that normal ordering is not a linear operation and normal ordering of a function of operators is not always well defined… but now I’m going into too much depth… The thing is that we now have operators that create excitations on our “vacuum”… However, in condensed matter this vacuum is not “the vacuum” whatever that means, but the set of particles you have there in your background… the movement of an excitation through this system (a.k.a. a collective excitation) can be quantized and can produce collective “particles” known as “quasiparticles”. They behave AS IF they were particles but in fact are collections of particles. Ok, the magnetic monopole in this case is just a specific configuration of the field generated by the spin structure in that object when the alignment did not reach a equilibrium. A hedgehog structure emerges for some time and it’s “pictured” as a monopole. Anyhow, a few days ago I started looking on facebook and people made me be careful and watch how they “discovered” the monopole… and of course, I said: “what? again?”… well, yes, this time not in a spin ice system but in a bose-einstein condensate… oh dear! I am about to fall of my chair… well… maybe not… 

Magnetic monopoles however, the true ones, the ones coming from vacuum don’t exist in nature… magnetic lines are always closed… well, Dirac was of course right: you can quantize a theory with magnetic monopoles and there is no problem or contradiction in doing so but they are not realized in nature for some reasons (about which I won’t talk now and here, as they reflect my own personal research and that has to be published first). String theory loves magnetic monopoles… not the ones discovered now, but the real ones that should be… around 1 per universe… so, keep searching… funding is assured! 



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