In the standard model, the origin of the values of the coupling strengths is mysterious. It takes only a few seconds to understand that GUTs do not solve the problem; they just shift the solution away. The same is true for supersymmetric GUTs.
Also the number of particle generations is not explained. Of course, one can claim that the number comes from the GUT Lie group [insert you favorite one here]. But what determines the Lie group? GUTs do not provide an answer. Again, the solution of a problem is just shifted away, into a region of higher abstraction.
GUTs also have another tiny issue: all GUTS that have been tested contradict experiment.
Thus, GUTs do not solve any problem of the standard model. So why are they popular? Because there is a lack of better ideas. But if an idea does not work, we should drop it, not continue to pay attention to it.
GUTs and TOEs are funny: people try to unify things for the sake of unifying without a clue how "unifying" is described.
ReplyDeleteLet us consider two independent equations - one is a "mechanical" and the other is a "wave" equation:
m*d^2R/dt^2 = 0,
d^2Q/dt^2 + omega^2*Q = 0,
where R and Q are different variables. Are these equation coupled? No. So we consider them as describing independent systems. Free charge motion and free electromagnetic field amplitude dynamics are described with such equations. We imagine the charge and the field as completely independent systems.
On the other hand, such equations can describe the center of inertia free motion and internal oscillations of a compound system. Now they are independent because they describe separated variable dynamics of one compound system. In this sense, they describe quasi-particles that belong to one system. They are not so independent, especially in presence of an external force.
An external force F(R) normally influences the center of inertia motion and pumps internal oscillations if it acts on a part of oscillator. How to describe it mathematically?
"Electrodynamically" understanding these equations leads to physical and mathematical problems whereas quasi-particle understanding gives reasonable results [1]. No strange Lee algebras are necessary to "unify" a charge and its quantized electromagnetic field.
[1] Reformulation instead of Renormalizations, http://arxiv.org/abs/0811.4416 .