# Questions tagged [gauge-invariance]

Invariance of a physical system (its action) under a continuous group of local transformations underlain by a global symmetry whose group parameters fixed in space-time have now been extended to vary in space-time instead. Use for buildup of the invariance, fixing the gauge, and accounting for the corresponding changes in the functional measure of the system.

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### Weak Equality & Strong Equality?

I have been trying to understand the meaning of these concepts: Weak $(\approx)$ and Strong $(=)$ Equality in the Dirac-Bergmann Algorithm for Hamiltonian Constrained Systems. I have already read ...
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### Definitions of different types of symmetries

I'm a math student and I started studying physics last year. I'm sorry if this question has been asked before but I'm completely confused about it. In page 30 of the book "String theory and M-...
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### Can we do Wilson RG in gauge theory in a gauge invariant fashion?

As we all know, cutoff regularization doesn’t work for gauge theory. So won’t the traditional Wilson RG work in gauge theory since it involves explicit cutoff for the same reason.
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### Independence of $S$-matrix of $\xi$-gauge in QED

On page 298 in Peskin and Schroeder, the authors attempt to argue that the $S$-matrix should be independent of the $\xi$-gauge in QED. However, I don't understand their argument, in particular the ...
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### Analog between Electromagnetism and Gravity

Feynman makes an analogy between EM field and gravity field in his Feynman's Lectures on Gravitation. The vector field representing EM potential would couple to the current source(vector) in the ...
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### Writing gauge transformation of the gauge fields explicitly in terms of coordinates

Let $G$ be a non-Abelian simple compact gauge group and $\{ t^\alpha\}$ be a normalized set of generators for its Lie algebra $\mathfrak{g}$. Let $C^{\alpha \beta}_\gamma$ be the coupling constant for ...
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