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[VĂdeo fet privat: Universeio - Gauge Theory] (ja el tornarĂ a penjar imagino).
Simetria Gauge en electromagnetisme
Concepte
“An example of a gauge symmetry is to describe a triangle by the positions of its vertices, the lengths of its sides and all of its internal angles. This represents a collection of 12 numbers that, if you think about it, represents a huge overcounting of how much information I need to uniquely distinguish my triangle from any other. As we know from elementary geometry, for example, we only need 3 numbers to distinguish any pair of triangles that we could draw on a piece of paper*. Clearly I could then change one or many of the 12 different numbers that I have and end-up describing exactly the same triangle. This is not a symmetry, like moving the lab around in the last example, it’s a redundancy. I simply have way more than the number of pieces of information required to describe what I’m trying to describe. This is what gauge “symmetry” is. I can treat a gauge symmetry like a genuine physical symmetry, and the end result is that, by running through Noether’s theorem again, I get a quantity that is conserved in time. The key difference here however is that, not being a physically relevant change of variables, the corresponding conserved quantity is zero for any physical process.