

Observation of Dirac monopoles in a synthetic magnetic field - rmserror
http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html

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fennecfoxen
The BBC coverage quotes a Lindsay LeBlanc, of the University of Alberta, "a
physicist not involved in the study":

"Although these results offer only an analogy to a magnetic monopole, their
compatibility with theory reinforces the expectation that this particle will
be detected experimentally."

[http://www.bbc.co.uk/news/science-
environment-25946734](http://www.bbc.co.uk/news/science-environment-25946734)

The overall phrasing seems to say that it's still just an analogue of a
monopole, but that it's a far more useful analogue in a system that you could
do meaningful experiments upon.

~~~
mjburgess
Physicists tend to be metaphysical sceptics on the whole, meaning that they
arent really convinced that the implied objects (/particles/fields/etc.) of
physical theories actually exist^. Merely that "something exists which makes
the mathematics work". Seeing so many different kinds of math work for the
same physical system tends to engender a kind of scepticism towards the
"metaphysical power" of mathematics to imply anything ontologically particular
about the world.

Now, when it comes to results like this, they are interesting because it
doesnt really matter if there are magnetic monopoles if you "just wanted to
use a magnetic monopole" \- you could create some in supfl. He.

The point is that whatever system enables the math to work is irrelevant to
what ever uses theories will have for this math.

Of course it is still practically relevant, because a simple monopole
experiment might be extremely expensive/difficult in Supfl. He.

NB^: Pop physicists who wax philosophical on TV shows tend to be sceptics but
appear "hardcore realists" for TV.

~~~
weland
> The point is that whatever system enables the math to work is irrelevant to
> what ever uses theories will have for this math.

Additional explanation from someone who (also?) used to do research, with
papers and all: we actually used objects we knew did not exist to do actual
science. By "do not exist" I mean "they are make-believe theoretical objects
that do not exist per se, but they are good _models_ for things that _do_
exist".

Science and engineering is full of these things. Holes in transistors: they
don't exist, they're actually a certain type of _electron_ shifting their
positions in a particular way, but the math would get a lot hairier (at no
gain!) if you treated them as electrons. Electrical charges in classic
electromagnetism aren't electrons at all -- they're small dots with charge on
them, but the math would get a lot hairier (at no gain -- again!) if you
didn't treat them like this.

Being able to model a phenomenon is very important, and being able to model it
_simply_ is, for lack of a better word, God-given. Phenomenological models
(i.e. models that model only the behaviour, not the inner working of a certain
phenomenon) are as good as any other model, as long as you bear in mind that
they are phenomenological: you can use them to reason about certain effects,
but not necessarily about what causes them.

Before anyone jumps in to point out this is bullshit and that there's really
more to life, I just want to remind everyone that we've been building
buildings and bridges and shit based on a phenomenological model. Classical
mechanics knows absolutely shit about how gravity works -- it just tells you
useful stuff about what it does -- and I'll personally grab all the beer in
the world for someone who finds an actual material point.

~~~
wbhart
I guess an electron is "an actual point".

~~~
weland
But it's not the only charge carrier. To put things in better context,
classical electromagnetism actually _predates_ knowledge about the structure
of atoms. The charges in its model are very much hypothetical particles, and
that's why it only really works at macroscopic scales. Turns out that's
actually enough for a lot of things :).

------
yew
Can anyone with a background in physics and/or interpreting _Nature_
publications comment on this? It appears to be a peer-reviewed publication,
rather than something merely published.

My understanding of Dirac's monopole hypothesis implies that these results
would be very significant for particle theory . . .

~~~
exmadscientist
This isn't a newly discovered fundamental particle. This is a new form of
behavior observed in ensembles of particles, in this case superfluid helium.
This is an exciting new result in condensed matter physics, not particle
physics. It's kind of surprising how much the mechanisms of particle physics
(gauge fields and all that) carry over to describing the collective behavior
of particles that's studied in condensed matter physics.

As to the sibling's comment from Lindsay LeBlanc, I don't believe that at all.
While true magnetic monopoles are allowed by our theories, we just haven't
seen any real evidence that they exist, and that's a bit strange. Personally,
I don't believe they'll ever be observed.

(I used to be a particle physicist, for what that's worth. Take my opinions at
face value!)

~~~
Steuard
I just came here to say pretty much exactly what you've already said (both
paragraphs, in fact). So I'll just chime in (as a physics professor and string
theorist) to endorse your take on the article.

This is a cool result, and it's neat to see a realization of the Dirac
monopole in a thoroughly quantum field. But it's _not_ a detection of a Dirac
monopole for the usual electromagnetic field (which would be an amazingly big
deal, and which I think most people don't ever expect to see).

~~~
officialjunk
The existence of a magnetic monopole would make maxwell's equations so much
prettier. Plus validate dirac's proof of why electric charge is quantized.
Sigh...

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archgoon
There's an additional article in Nature that describes the research:

[http://www.nature.com/news/quantum-cloud-simulates-
magnetic-...](http://www.nature.com/news/quantum-cloud-simulates-magnetic-
monopole-1.14612)

No it's not a monopole, Div B is still zero everywhere. Yes it is interesting.
:)

------
wfn
Full article for anyone curious:
[http://ge.tt/2O8mr1H1/v/0?c](http://ge.tt/2O8mr1H1/v/0?c)

~~~
wfn
(link seems not to work any longer, mirror:
[http://bayfiles.net/file/15Fqf/KfQTOj/nature12954.pdf](http://bayfiles.net/file/15Fqf/KfQTOj/nature12954.pdf))

