4 ms·

What exactly does it take for a thing to count as a fundamental force? I loosely associate forces with bosonic fields -- photons for EM, gluons for strong, and

What exactly does it take for a thing to count as a fundamental force? I loosely associate forces with bosonic fields -- photons for EM, gluons for strong, and something confusing for weak. But then no one seems to want to call the Higgs field a "force".

jessriedel 10y ago
This is an good question which I'm sure there is a good answer for, but which I haven't heard stated by particle physicists in a clean way that is widely accessible to other physicists. I believe the distinction generally hinges on whether the boson is a gauge boson, associated with some symmetry; this does not apply to the Higgs. But I don't really get why that makes it worthy of the intuitive label "force". Here's one incomplete answer: > Q: Why isn't Higgs coupling considered a fifth fundamental force? > A: The Higgs exchange between matter particles can certainly be called a force. Whether it can be viewed a fundamental force, is a matter of taste. But there is one important distinction between the force due to the Higgs exchange and the usual fundamental interactions. The strong and electroweak interactions are described as gauge interactions. It means that they are not put by hand but arise automatically when you require that the matter fields be invariant under local certain internal transformations (phase rotations, color transformations, etc.). In contrast to that, the "Higgs force" is put into the model by hand, as its presence is not driven by any symmetry consideration. You can equally nicely consider a model with zero Yukawa coupling. http://physics.stackexchange.com/questions/1080/why-isnt-higgs-coupling-considered-a-fifth-fundamental-force http://physics.stackexchange.com/questions/1080/why-isnt-hig...
- tamana 10y ago
  What are the non-fundamental forces? If they are not fundamental, does that mean physicists suspect they are complex interactions of other, fundamental forces?
  - semi-extrinsic 10y ago
    Physicists will typically say "friction force", or "van der Waals force", or "centrifugal force" etc. when we talk about the interactions of ordinary things. These are all caused by the four fundamental forces (or they are ficticious, like the centrifugal force). And yes, the non-fundamental forces (like friction) are complex interactions of fundamental forces. For friction it's the sum of electric forces between atoms. The important point is that an atomistic model of friction gives you an essentially unsolvable problem, while the effective macroscopic model of friction is high school stuff.
    - hackney 10y ago
      Unsolvable? Rubbish. I was under the impression with regards to the 4 forces that the only mystery was the mathematical relationship bewteen electricity and gravity. I'm sure it is not as big a mystery as popular science would have us believe.
      - semi-extrinsic 10y ago
        When I say unsolvable, I mean that you can't solve for the speed of a brick sliding down an inlined plane by considering the electrostatic interactions between the ~10^17 pairs of interacting atoms per square centimetre of contact surface. It's just unsolvable in practice. But the effective formula that the magnitude of the friction force equals a material constant times the magnitude of the normal force from the plane onto the brick gives you a very simple model (solvable with pen and paper).
        hackney 10y ago
        I kind of figured no one would want such a crude result. That would be more like fluid friction dynamics. Thank you for elucidating.

jessriedel 10y ago

This is an good question which I'm sure there is a good answer for, but which I haven't heard stated by particle physicists in a clean way that is widely accessible to other physicists. I believe the distinction generally hinges on whether the boson is a gauge boson, associated with some symmetry; this does not apply to the Higgs. But I don't really get why that makes it worthy of the intuitive label "force". Here's one incomplete answer: > Q: Why isn't Higgs coupling considered a fifth fundamental force? > A: The Higgs exchange between matter particles can certainly be called a force. Whether it can be viewed a fundamental force, is a matter of taste. But there is one important distinction between the force due to the Higgs exchange and the usual fundamental interactions. The strong and electroweak interactions are described as gauge interactions. It means that they are not put by hand but arise automatically when you require that the matter fields be invariant under local certain internal transformations (phase rotations, color transformations, etc.). In contrast to that, the "Higgs force" is put into the model by hand, as its presence is not driven by any symmetry consideration. You can equally nicely consider a model with zero Yukawa coupling. http://physics.stackexchange.com/questions/1080/why-isnt-higgs-coupling-considered-a-fifth-fundamental-force http://physics.stackexchange.com/questions/1080/why-isnt-hig...

tamana 10y ago
What are the non-fundamental forces? If they are not fundamental, does that mean physicists suspect they are complex interactions of other, fundamental forces?
- semi-extrinsic 10y ago
  Physicists will typically say "friction force", or "van der Waals force", or "centrifugal force" etc. when we talk about the interactions of ordinary things. These are all caused by the four fundamental forces (or they are ficticious, like the centrifugal force). And yes, the non-fundamental forces (like friction) are complex interactions of fundamental forces. For friction it's the sum of electric forces between atoms. The important point is that an atomistic model of friction gives you an essentially unsolvable problem, while the effective macroscopic model of friction is high school stuff.
  - hackney 10y ago
    Unsolvable? Rubbish. I was under the impression with regards to the 4 forces that the only mystery was the mathematical relationship bewteen electricity and gravity. I'm sure it is not as big a mystery as popular science would have us believe.
    - semi-extrinsic 10y ago
      When I say unsolvable, I mean that you can't solve for the speed of a brick sliding down an inlined plane by considering the electrostatic interactions between the ~10^17 pairs of interacting atoms per square centimetre of contact surface. It's just unsolvable in practice. But the effective formula that the magnitude of the friction force equals a material constant times the magnitude of the normal force from the plane onto the brick gives you a very simple model (solvable with pen and paper).
      - hackney 10y ago
        I kind of figured no one would want such a crude result. That would be more like fluid friction dynamics. Thank you for elucidating.