# Tag Info

### Mass terms for scalar lagrangians?

I'm a little rusty on this (since 2008, it's 2022) and I am not an expert, but a vector boson should have a field $A^\mu$ or $G_a^\mu$ depending whether it's a photon or a gauge boson, where the $\mu$ ...
1 vote

### Could there be some process or event that would make the universe to be Lorentz non-invariant?

It depends on what you mean by "could". "Could there be any process or event that would violate all these symmetries, based on what we know today?" NO, otherwise we wouldn't derive ...
• 4,630
Accepted

### Confusion about symmetry spontaneous breaking in a simple model

The question is based on misinterpretation of the meaning of terms symmetry and spontaneous symmetry breaking. Symmetry The Hamiltonian in the OP possesses a rotational symmetry (note that all this is ...
• 37.4k

### Confusion about symmetry spontaneous breaking in a simple model

This system won't exhibit spontaneous symmetry breaking (SSB). You need the thermodynamic limit in order to see SSB. The point is that in an infinite system, even though the degenerate ground states ...
• 710
1 vote

### Symmetry breaking in near free electron?

Translational symmetry is broken: instead of the invariance to arbitrary translations the system is no invariant only to the translations by a multiple of the lattice vector. In fact, what we have ...
• 37.4k
1 vote
Accepted

### Quantum Time Crystals

He is referring to a more precise definition of order parameter. The idea is to capture spontaneous symmetry breaking: the ground states of the system are not individually invariant under the ...
• 1,157

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