# B Standard model particle properties

1. Jan 29, 2017

### calinvass

In the Standard Model, for any particle, I have only found properties related to electromagnetic and gravitational (in fact mass does not necessarily mean it is a property related to gravity, but to emergy)forces like charge and mass.
Why there isn't anything about the other two interactions like strong and weak. ?

Last edited: Jan 30, 2017
2. Jan 30, 2017

### Orodruin

Staff Emeritus
What do you mean? What properties are you referring to? Gravitation is not part of the standard model. The weak and strong interactions are. Please provide references to your statements.

3. Jan 30, 2017

### calinvass

Yes, I also said, mass is not necessarily related to gravity but to energy.
I mean a property like weak charge or strong charge.

4. Jan 30, 2017

### calinvass

Yes, I also said, mass is not necessarily related to gravity but to energy. Anyway gravitation apears as one of the four fundamental forces:https://en.m.wikipedia.org/wiki/Standard_Model#
I mean a property like weak charge or strong charge.

5. Jan 30, 2017

### Orodruin

Staff Emeritus
The reason you do not find it is that it is not that simple. It is rather easy to talk about the electromagnetic charge, but the strong and weak forces have a fundamentally different behaviour. On top of that, the weak force is the residual of the broken electroweak symmetry.

For the strong force, the charges are essentially the quark colours. For the weak interactions, it is even more complicated as it only couples to left-handed particles and the corresponding charge is whether or not the particles are up or down type in the case of the quarks and neutrino or charged lepton in the case of the leptons. The fundamental reasons for this cannot be covered at B-level.

6. Jan 30, 2017

### calinvass

Is there any evidence that these are fundamental forces with a high degree of certainty?

7. Jan 30, 2017

### Orodruin

Staff Emeritus
You can never prove anything with certainty in physics. The best you can do is to check whether or not your theory gives a good description of what you can observe in Nature and the standard model is very accurate. Of course, when we get more sensitive experiments, it may very well turn out that it needs to be modified.

Also, it is more correct to talk about fundamental interactions rather than forces, as forces generally seem to imply some sort of classical force. At the level that strong and weak interactions are relevant, the interactions generally need to take quantum effects into account.

8. Jan 30, 2017

### Staff: Mentor

Depends on what you call "fundamental".

The electric and the magnetic forces were combined to the electromagnetic interaction. The electromagnetic interaction and the weak interaction were combined to the electroweak interaction.
It is expected that the electroweak interaction and the strong interaction can be combined as well ("grand unified theory" - GUT), and an additional possible step would be a unification of GUT with gravity ("theory of everything" - TOE).
What is fundamental now? The fully unified interaction? Or the interactions we see in our world at low energies?

9. Jan 30, 2017

### nikkkom

Your statement, while mathematically correct, may lead some to a false assumption that "physics never gives us final results". But it sometimes does. Sometimes "uncertainty" is so tiny that it can be disregarded. Some parts of physics knowledge, after many years, become pretty certain (having overwhelming evidence) and won't be disputed, ever. Two random examples:

- We know for certain that matter does consist of atoms (IOW: "atomic theory" indeed was a theory up to ~1800, but now it's a fact).

- We know for certain that those tiny shining apparently motionless specks in the night sky are far away large objects similar to our Sun.

These theories can only be disproved, perhaps, only by a drastic discovery like "we do live in a simulated reality! Matrix is real!"

10. Jan 30, 2017

### Orodruin

Staff Emeritus
I am not talking about such things, I am talking about what can be considered a "fundamental" theory. We know that matter consists of atoms, but the atom theory in itself was originally designed with the atom as the smallest "unbreakable" fundamental unit. We know today that the atom is not fundamental and my point is that you can never know if you have really gotten to the fundamental level or not.

Correspondingly, at some level it is sufficient to describe a star as a light source with some mass and intensity, but at a more fundamental level we know that it consists of a fusion plasma where the pressure from internal fusion reactions balance the gravitational forces.

11. Jan 30, 2017

### nikkkom

Imagine this. It's year 2917, there is a model of particle physics (perhaps not too drastically modernized Standard Model of those primitives from 2017) which explains everything, allows to calculate scattering and other experimental results with astounding accuracy (thousands of digits) and all attempts to find a robust discrepancy with ever more precise experiments are failing, century after century.

Can people living in that year know that they really got to the fundamental level?

Mathematically speaking, no. The model may still be not a final answer but only an approximation.

However, on a practical level, in the above hypothetical scenario the interest to that question will be about as lukewarm as my interest to the question "do we live in a perfectly simulated Universe?". I can never prove we aren't, but so what?

12. Jan 30, 2017

### Orodruin

Staff Emeritus
Which kind of just makes my point.

However, as even better colliders become available, this "new standard model" can be even further tested to find out whether there are regimes where it is no longer a good approximation - which is exactly what we are doing in accelerators today. We know that the standard model is a good description in (most of) the situations we have checked. If we are happy with that level of description, we could stop there. But we are curious and continue to try to push the boundaries and to see whether or not it remains a good description under more extreme circumstances.

13. Jan 30, 2017

### nikkkom

Situation with current SM is different. It's not curiosity which drives the desire to find a theory better than SM.

Current SM, while explaining a lot, has a number of problems which don't allow to seriously consider the possibility that it can be a final theory.

14. Jan 30, 2017

### calinvass

For example, I don't see temperature as fundamental. I understand fundamental as something that can't be further divided into simpler elements. However, using current accepted knowledge we cannot divide it, it can be considered as fundamental but not necesarily as final answer of physics but as a final answer of the theory.

I can think of another criteria: the fumdamental element should have enough properties to properly describe the theory that supports the concept of the element.

I understand combining electric and magnetic interactions into EM the same way we can use a complex number having an real and an imaginary part. Although we call one of them imaginary the parts are both real in a mathematical context.

Last edited: Jan 30, 2017
15. Jan 30, 2017

### ZapperZ

Staff Emeritus
This is really philosophy.

Do you have a physics question that you wish to ask?

Zz.

16. Jan 30, 2017

### calinvass

Sorry.

That is all, thank you.