Why EM and weak interaction are unified

In summary, people say that the ##SU(2)\otimes U(1)## theory unifies the EM and weak interactions in the Standard Model. However, this unification is not as complete as in Grand Unified Theories (GUTs) since the electroweak theory still has two independent gauge groups and couplings. While the weak and EM couplings are the same at a high unification scale, they have different dependencies at low energies.
  • #1
karlzr
131
2
In SM, people say the ##SU(2)\otimes U(1)## theory unify the EM and weak interaction. I understand that the two interactions both originate from the electroweak theory in a mixed way. But does this mean they are unified? Since when we talk about unification like GUT, we require the couplings run to the same value at a high unification scale. I don't see it in electroweak theory. So how should we interpret the difference?
 
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  • #2
Yes, you can justifiably complain that the electroweak theory does not really unify anything since it still has two independent gauge groups, SU(2) and U(1), with independent couplings. Ideally we might have hoped that both forces would arise from a single gauge group. GUTs are more ambitious and seek to derive the SU(3), SU(2), and U(1) of the Standard Model from a single gauge group.
 
  • #3
The weak and EM couplings are the same alpha=1/137. However the weak interaction depends on
alpha/(M_W^2+Q^2), while EM is alpha/Q^2, so the weak looks weak at low energies.
 

1. Why are electromagnetism and weak interaction considered to be unified?

Electromagnetism and weak interaction are considered to be unified because they are both fundamental forces of nature that govern the behavior of subatomic particles. They were initially thought to be separate forces until it was discovered that they can be described by the same mathematical framework, known as the electroweak theory.

2. What evidence supports the unification of EM and weak interaction?

The main evidence supporting the unification of electromagnetism and weak interaction is the discovery of the W and Z bosons, which are particles that mediate the weak force. These particles were predicted by the electroweak theory and were later confirmed by experiments at the Large Hadron Collider (LHC).

3. How does the unification of EM and weak interaction relate to the Standard Model of particle physics?

The unification of electromagnetism and weak interaction is an important part of the Standard Model of particle physics. This model describes the fundamental particles and forces of nature, and the unification of EM and weak interaction is one of its key principles.

4. What is the role of the Higgs field in the unification of EM and weak interaction?

The Higgs field is an essential component of the electroweak theory and plays a crucial role in the unification of electromagnetism and weak interaction. It gives mass to the W and Z bosons, which are necessary for the weak force to have a short range and for the unification of the two forces to occur.

5. Can the unification of EM and weak interaction be tested further?

Yes, scientists are still conducting experiments and research to further test the unification of electromagnetism and weak interaction. This includes studying the properties of the Higgs boson and searching for new particles and phenomena that may provide evidence for the unification of these two forces.

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