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We have unified electromagnetic and weak force into one single force called Electroweak force.

I mean we can use these different forces within their respective domains like weak interaction for short range effects and electromagnetic for long range effects.

Does Electroweak force reduces to weak force at short range and reduces to electromagnetic force at long range? or We observe different phenomenon when we combine different forces into one single force(like Electroweak force) ?

As weak force is short range and electromagnetic is long range, what's the range of Electroweak force?

Qmechanic
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Gary Grey
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Theoretical physicists love symmetries and using very few assumptions to describe Nature. For example, people knew that there is "some force" that attracts an apple from the tree and there exists "some force" that binds the moon to the earth. But Newton realized they are the same force and their actions are described by the same simple law which is called law of gravity. This is the beauty that (theoretical) physicists are aspire to. They want to blend all the forces in Nature into One. That is, of course, an ambitious project.

The most fundamental step in this direction was taken by Maxwell when he unified electricity and magnetism together. That's not only beautiful but it gives us more understanding of Nature itself. We know now (after special relativity) that magnetic fields and electric fields are not fundamental objects but, rather, which one you perceive depends on your frame of reference.

The same logic works for any unification. It makes you understand the rules of the game (of Nature) much better than before.

About the electro-weak force, the unified theory is valid in high energy scales (around 100 GeV). Then it "breaks down" into Maxwell and Weak interaction as one goes to lower energy scale.

David Richerby
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Physics Moron
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  • Thanks, around 250 GeV, we must use Electroweak force to understand what's going on and we cannot apply either electromagnetic or weak force to understand the phenomenon at around 250 GeV? – Gary Grey Aug 18 '15 at 19:47
  • @GaryGrey I think I got the number wrong. That should be around 100 GeV. Actually 250 GeV is the electro-weak scale i.e, the Higgs VEV. Yes, at high enough energy underlying symmetry enhances and one needs to describe phenomena at that scale using the unified theory viz. electro-weak theory. – Physics Moron Aug 18 '15 at 20:07
  • Thanks again,And when we say Maxwell's equations(https://en.wikipedia.org/wiki/Maxwell%27s_equations_in_curved_spacetime) or Quantum field theory(https://en.wikipedia.org/wiki/Quantum_field_theory_in_curved_spacetime) in curved spacetime.What does this mean? Does it mean that we have unified QFT or Maxwell's equations with general relativity? And how this is different from unification of forces i.e. how QFT or Maxwell's equations in curved spacetime is different from unifying electromagnetism or QFT with general relativity? – Gary Grey Aug 18 '15 at 20:28
  • Maxwell's theory of electromagnetism is itself a QFT. QFT in curved spacetime doesn't mean unification. That actually means we are doing QFT (which is a quantum theory of fields) in classical background which is curved. That's all. The metric is not fluctuating. – Physics Moron Aug 18 '15 at 20:35
  • Can you explain this in detail,with an analogy? – Gary Grey Aug 18 '15 at 20:57
  • For example if one studies real scalar field in flat Minkowski space the Lagrangian (density) will be : $\eta_{\mu \nu}\partial^\mu \phi \partial^\nu \phi - m^2 \phi^2$. One can quantize it easily. For curved space one usually assumes the space doesn't fluctuate rapidly (Born-Oppenheimer type approximation) and treats the metric classically. So one just replaces the Minkowski metric by some curved one ($g_{\mu \nu}$). So the Lagrangian becomes $g_{\mu \nu}\partial^\mu \phi \partial^\nu \phi - m^2 \phi^2$. Then quantizes the field $\phi$. – Physics Moron Aug 18 '15 at 21:05
  • Maxwell's theory isn't a quantum theory — it's purely classical. – Ruslan Jun 13 '16 at 15:47
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    Special relativity is a direct consequence of the Maxwell equations, and curved spacetime is a Generalisation of that. None are quantised. – OrangeDog Jun 13 '16 at 17:25