I was trying to think of something deep and meaningful to post today, but I've been in conference mode too long to do anything all that deep. So here's a simple binary choice for all the nerds in the audience:
Bosons or fermions?
It's a tough call after a few days of conferencing: On the one hand, I'm typing this Thursday night, and I'm about to head out to get a few more beers, so I can appreciate the sociable nature of bosons, but then again, another day of this, and I may not want to talk to anyone at all next week. Plus, fermions in a spin-polarized sample are absolutely forbidden from colliding at low temperatures, and how cool is that?
What's your favorite category of particle?
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Fermions. But I always try to go against convention.
Bosons or fermions?
Maybe.
So two fermions walk into a bar. And the first one says to the bartender, "I'll have a gin and tonic". And the second one says, "shit, that's what I wanted!".
jeffk:
The two fermions can have the same drink, but they have to spin on their barstools in opposite directions.
And then one of them gets into a barfight and ends up a particle with fractional statistics.
Wasn't this already settled in the Spring Science Showdown?
As one of Fermi's academic descendants (although a disappointing one, at that), I have to go with fermions. Plus, it's pretty cool that spacetime in 2D string theory is just the Fermi surface of a large number of non-interacting particles...
Fermions, without a doubt.
Have you ever noticed how people fill up the empty seats on a bus...
Anyons.
As John Baez says (excerpted):
http://math.ucr.edu/home/baez/braids/node2.html
We all know that particles come in two fundamentally different flavors: bosons and fermions. The argument for this is simple, well-known, and a bit misleading. It goes like this. Say we have a bunch of $n$ identical particles. Their state is described by a wave vector (a vector in a complex Hilbert space). We may permute the particles without really doing anything since they are identical, you can think of it as just permuting their ``labels''. Now in quantum mechanics two wave vectors which differ only by a phase (a scalar factor of unit modulus) describe the same physics. Thus we must have a representation of the symmetric group $S_n$ on the Hilbert space, and it must map any permutation to a scalar multiple of the identity. There are only 2 such representations (another charming exercise): the trivial representation and the one mapping each permutation to its sign. In the former case we say the particles are bosons, and in the latter, fermions.
This seems to be the case in reality. Interestingly, all the fundamental particles one might call ``matter'' are fermions (quarks and leptons), while all the particles one might call ``force fields'' are bosons (the photon, W, Z, and gluons). Here of course I am skirting the issue of the Higgs particle, that curious fudge factor. If the Japanese decide to pay for the superconducting supercollider we will see if the Higgs exists.
If one pays close attention to the argument, however, it's full of holes. First of all, why do we really need a representation of $S_n$ -- in quantum mechanics a projective representation is good enough! Secondly, if one considers representations where $S_n$ does not act as scalars but as an ``internal symmetry group'' one gets even more possibilities. These were investigated under the name of parastatistics. Anyway, one can come up with a better argument, the spin-statistics theorem, in relativistic quantum field theory, and that, together with the fact that parastatistics can be redescribed as fermions and bosons in disguise, seems to give a solid explanation for why all we see is bosons and fermions. (Though I couldn't say I'm very familiar myself with the whole story.)
Now for the catch: the spin-statistics theorem only holds for spacetimes of dimension 4 and up. You could just say ``thank heavens! that just happens to apply to our universe!'' and leave it at that, or you could note that it's occaisionally [sic] possible to simulate universes of lower dimension. Take, for example, a thin 2-dimensional layer of stuff: this can act like a little 3-dimensional spacetime. Similarly, filaments can act like 2-dimensional universes. These days condensed matter theorists delight in the odd processes that occur in these contexts, and it was only a matter of time before someone noted that one can, at least in principle, arrange to get particles that are neither bosons or fermions. Wilczek is generally credited with taking the idea of these ``anyons'' seriously, though it had occured to others earlier.
but Howard Georgi says I don't HAVE to be a particle...
Fermions for the belt trick, but Bosons when I'm trying to be cool.
anyons are not hypothetical. they are the elementary excitations of fractional quantum hall states. their fractional statistics have recently been measured via aharonov-bohm interference.
i'm with jonathan. anyons are my favorite
I vote for supersymmetry, so they are both the same (in a manner of speaking).
I vote for supersymmetry, so they are both the same (in a manner of speaking).
Supersymmetry is not a type of statistics!
In supersymmetry bosons and fermions are not the same. It is true that the multiplets include bosons and fermions, but bosons still satisfy bosonic statistics and fermions fermionic statistics.