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1
vote
1answer
108 views

Why does gauge invariance HAVE to correspond to an observable?(Or is it the other way round)

Under the line integral of the geometrical Berry phase, a close-loop integral is gauge invariant as if we were to perform a gauge transformation of the initial state, with the end point of the path in ...
3
votes
2answers
455 views

The location of an object is gauge dependent. Therefore, it's not measurable?

The location of an object $x$ depends on how we choose our coordinate system. If we move the zero point, $x$ also changes. However, since we have translational invariance, we can always do such shifts ...
5
votes
2answers
229 views

Question about Charge and Gauge Transformation

Does gauge invariance imply charge neutrality? I understand that all physical observables must be gauge invariant. Does this mean that physical observables must be neutral? If a quark is in red, a ...
3
votes
1answer
93 views

Is direct observation of strong and weak force ruled out by quantum field theory?

In quantum field theory electromagnetic radiation is described by a theory with an abelian gauge symmetry while the weak and strong force are described by theories with non abelian gauge symmetry. We ...
3
votes
1answer
79 views

What are the measurable quantities in General Relativity?

What are the quantities in GR that one can actually measure in an experiment? It seems scalars, being coordinate independent, should be measurable. What about other quantities? For example, using only ...
5
votes
1answer
170 views

Experimentally distinguishing between topologically inequivalent physical states in gauge theory

In gauge theory, physical states are often said to be characterized by equivalence classes of gauge field configurations that differ by gauge transformations. But according to Large and small gauge ...
3
votes
1answer
270 views

In what types of QFTs are the Wilson loops of interest?

I have a very basic question about Wilson lines (WL). This is what I know about the WL: WL help us to learn about the important properties of gauge fields (treated as connections on the space of ...
2
votes
1answer
405 views

Lagrangian gauge theory with physically observable local degrees of freedom

In my answer at What, in simplest terms, is gauge invariance?, I mentioned that in certain contexts there can be a "gauge theory" with a local symmetry that leave the Lagrangian/Hamiltonian invariant ...
0
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1answer
72 views

Gauge Bosons at Finite Temperature

I was reading a paper¹, and it states: " Therefore, the gauge fields themselves cannot be entities of the physical reality, as any observations should be independent of the chosen gauge" I'm trying ...
2
votes
1answer
262 views

About states, observables and the wave functional interpretation in QFT with gauge fields

First of all, I'm a mathematician, so forgive me for my possible trivial mistakes and poor knowledge of physics. In a QFT, we just start with a field (scalar, vectorial, spinorial, gauge etc), so I ...
7
votes
1answer
770 views

Does spontanous symmetry breaking affect Noethers theorem?

Does spontanous symmetry breaking affect the existence of a conserved charge? And how does depend on whether we look at a classical or a quantum field theory (e.g. the weak interacting theory)? (In ...
5
votes
2answers
821 views

Diff(M) and requirements on GR observables

This question is kind of inspired in this one: Diff(M) as a gauge group and local observables in theories with gravity The conundrum i'm trying to understand is how is derived the (quite) ...