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How Many Elementary Particles Are There, Really?

quantamagazine.org

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Re: How Many Elementary Particles Are There, Really?

#51

Post by slashdave »

BobbyTables2 wrote: post #4

Not being a Physicist, I have to wonder if all these particles are somehow manifestations of a simpler thing. Might there have been a point in time (long ago) where the “wave photon” and the “particle photon” seemed like possibly different things?

> I have to wonder if all these particles are somehow manifestations of a simpler thing

Yes, theorists have been working on a similar idea for decades.

> the “wave photon” and the “particle photon” seemed like possibly different things?

No. Wave vs particle is just a different description of the same thing.

Re: How Many Elementary Particles Are There, Really?

#52

Post by d4ng »

slashdave wrote: post #49
d4ng wrote: post #30

There are also 17 wallpaper groups. That always seemed like a funny number. I know it's a long shot, but is there a relation?

Funny to who? The decimal system, for example, is a human invention.

It's a reasonably sized prime number regardless of base.

Re: How Many Elementary Particles Are There, Really?

#53

Post by tlogan »

eximius wrote: post #43
tlogan wrote: post #32

D

Hmm if a particle is a quantized packet of a field, then if multiple quantizations are possible in a field, then it's possible for more particles than fields?

I somehow deleted my original comment.

I actually made mistake. There are 16 fields:

* 12 matter fields (6 quarks + 6 leptons)

* 1 gluon field (an 8-component SU(3) field)

* 1 weak field (a 3-component SU(2) field)

* 1 hypercharge field (a 1-component U(1) field)

* 1 Higgs field (SU(2) x U(1))

We have 17 particles is because W+, W-, Z are combination on 2 fields.

I think counting particles is just going to confuse people because they are really not “balls”.

Re: How Many Elementary Particles Are There, Really?

#54

Post by unholiness »

pdonis wrote: post #40
unholiness wrote: post #33

Stopped reading after "Yet in the mathematical equations that define the Standard Model, the eight gluons are distinct from one another in the same way that the W and Z bosons differ." W and Z bosons, photons, etc have fixed masses, charges, interaction strengths with other particles. These properties can exactly be listed and looked up in a table of elementary particles with discrete rows. Gluon color is continuous…

> W and Z bosons, photons, etc have fixed masses, charges, interaction strengths with other particles. But you can form a continuous set of linear combinations of these things, just as you can with gluons. Indeed, what the article calls W and Z bosons (and photons) are just such linear combinations--the ones that appear in the low energy limit after the electroweak phase transition occurs. Before that phase transitio…

In a hypothetical scenario where we were inventing the standard model in the first 10^-11 seconds after the big bang, you're right there would be an analogy there. But in that scenario, our standard model would say there was one electroweak particle, not that there were 8 gluons.

In our own universe, the fact that electroweak symmetry breaks ensures there are 4 electroweak particles and not other combinations. There's no corresponding thing to contain gluons to individual particles, you'd need laws of physics we don't have to add that constraint.

Re: How Many Elementary Particles Are There, Really?

#55

Post by dpark »

antonvs wrote: post #21
TheOtherHobbes wrote: post #18

Earlier quoted context omitted.

In QFT every particle type has its own field.

Every particle type has its own field, but the OP article is counting a single particle type multiple times based on properties like spin and polarization. At one point the article reaches the number 118. That corresponds directly to 37 quantum fields once you take the "double counting" into account.

Where are you getting 37? The standard model has 17 fields.

If you pick and choose which properties to select as unique fields, maybe you can get the number 37, but at that point why not 118 fields?

Re: How Many Elementary Particles Are There, Really?

#57

Post by Alulim »

I'm not a physicist (so take this with a grain of salt) but I have spent a lot of time trying to find an answer to this question. If you interpret the physics before Spontaneous Symmetry Breaking as more fundamental, and you treat the antimatter fields as distinct, then I think you can reasonably claim that there are 30 fundamental fermion fields. Specifically, in each of the 3 generations, you have:

1. The left-handed lepton doublet field, and the antimatter equivalent. 2. The left-handed quark doublet field, and the antimatter equivalent. 3. The right-handed electron singlet field, and the antimatter equivalent. 4. The right-handed up-quark singlet field, and the antimatter equivalent. 5. The right-handed down-quark singlet field, and the antimatter equivalent.

The bosons are more confusing to me, but I think a reasonable person might say that there are 16 fundamental boson fields:

1. The four scalar boson fields. 2. The eight gluon fields. 3. The three W boson fields. 4. The B boson field.

The B boson couples to every fermion (via hypercharge), while gluons only couple to quarks (via color) and W bosons only couple to the doublets (via weak isospin).

Re: How Many Elementary Particles Are There, Really?

#58

Post by sva_ »

d4ng wrote: post #52
slashdave wrote: post #49

Earlier quoted context omitted.

Funny to who? The decimal system, for example, is a human invention.

It's a reasonably sized prime number regardless of base.

> reasonably sized prime number

I feel like you're alluding to something but won't say to what? Maybe something like the 'fine-tuned universe' hypothesis?

Re: How Many Elementary Particles Are There, Really?

#59

Post by GistNoesis »

tsimionescu wrote: post #31
HarHarVeryFunny wrote: post #26

Earlier quoted context omitted.

But of course one can then question why are there exactly N different types of fields, with their specific types of interaction (at least in our universe)? Why should we suppose that this is the most fundamental description of reality, rather than being emergent from something else?

Well, why would there be fewer than N? There is no general principle that we can impose on the world, it just is, we can only discover what the laws and components of the world are (hopefully). I'm not claiming it's impossible for there to be fewer fields than we think right now. But there is no reason to believe there should be.

Elegance. It's Occam's razor. If we can do with only one field, it's probably it.

It's inductive and abductive reasoning. The one field, and it has lot of mathematical characteristics which makes it unique on its own, and also it is the only one that has a chance to fit, is the e8 field popularized by Garrett Lisi.

If a universe were to be designed based using the e8 Lie algebra as an elemental field, it would look a lot like our universe.

Currently the standard model is a patchwork of field added as experiments for observing particles were possible to realize. The big picture's view is a unified theory which fits perfectly all existing data.

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