Freebase: Discussion about Field Of Study

Particle physics: Particle type?

2009-12-17T18:30:39.0013Z

If weight weren't attached to the composition, it would be modeled as we have it. The variant weights per composition makes it rather harder; I can't think of another solution yet, but I'll keep thinking about it. (We could also just go with what we have, and add composition later.)

Particle physics: Particle type?

2009-12-17T14:23:08.0005Z

Small bump here to keep this moving.

I've added a boolean "Self antiparticle" to the particle type and filled it in appropriately. It's not a perfect solution, but at least it lets us get the data into the graph. Still wondering what to do about the composition of π⁰.

Particle physics: Particle type?

2009-12-07T22:12:10.0022Z

Phil: Ahh, I see. There is no way to make a model like that which will work in the client. MQL doesn't care about nested CVTs, but the client balks at them.

Particle physics: Particle type?

2009-12-06T18:40:32.0008Z

Jeff: composition is already non-unique. Ideally, what I'd like to end up with is something like the structure pictured here, but none of the "xxx" nodes make sense to be topics themselves.

Particle physics: Particle type?

2009-12-05T11:00:08.0020Z

I've deleted particle statistical family and group - the particle type is looking nice and clean now.

For π⁰, I guess we could have a formula (i.e. text) similar to a chemical compound formula, but then we lose the linkage to the quarks it makes up. Otherwise I think we'll have to leave composition of π⁰ etc and self antiparticles as open questions for now.

Another question: why doesn't the Browse view for an Electron display its particle properties?

Particle physics: Particle type?

2009-12-04T18:37:21.0013Z

Composition of π⁰: Could composition be non-unique, and defined as "possible compositions"?

Particle physics: Particle type?

2009-12-04T12:05:57.0011Z

I've added particle family to the particle type so I think we can now drop particle statistical family and group. I've also engaged in some property reciprocation.

Self antiparticles: ugh. The double links solution is pretty horrible. The only other solution I can think of would be to have a "self antiparticle" boolean, but that's probably even worse.

Composition of π⁰: in slight handwaving terms, the π⁰ can be thought of as alternating between being composed of (an up quark and an up antiquark) and (a down quark and a down antiquark), but never (an up quark and a down antiquark) or any of the other combinations. The only ways I can see to model this either end up with CVTs inside CVTs or creating a topic for something like "composition of the π⁰".

Spin: yeah, I screwed up the pion spins. Good catch. Now fixed, I think.

Particle physics: Particle type?

2009-12-04T00:49:03.0013Z

I like the hadron type!

I've changed spin to float and updated the spins that were already entered in (note: Wikipedia says pions have zero spin? also, should spins be negative?). I'll start moving types from my base to the new base soon.

Particle physics: Particle type?

2009-12-03T18:48:31.0031Z

Self antiparticles: There isn't a way to set a particle to be its own antiparticle using a sibling-relationship CVT -- the CVT has only one property to hold both particles, and you cannot enter the same topic as a value for a property more than one time. The only work-around would be to use something that resembled a phylogeny pattern, with two linked properties "antiparticle" and "antiparticle of". This is kind of ugly, but would handle the π⁰ case. The problem with this pattern is that you have to enter all the relationships in twice for all particles that aren't antiparticles of themselves -- once in the "antiparticle" property, and once in "antiparticle of".

Composition of π⁰: I'm not sure what "linear combination of (up-antiup) and (down-antidown)" means, but I can see in Wikipedia's list of mesons that there are several mesons with similarly complex compositions.

Uncertainties: we can do this -- see how we handled it for atomic masses.

Spin: Agreed -- let's make it just be a float for the particles. We can refactor the Particle Spin type separately.

Particle physics: Particle type?

2009-12-03T13:07:45.0013Z

More from me... it doesn't at the moment to seem possible to set a particle to be its own antiparticle (try it with the π⁰). Any thoughts on a way round this one?

Also, we need to find a way to model the composition of the π⁰, which is a linear combination of (up-antiup) and (down-antidown).

I'll shut up for a bit now and let other people get a word in edgeways :-)