Gauge Fixing Term: Physical Effects & Role in Spin Components

In summary, the purpose of a gauge fixing term is to eliminate unnecessary spin components from the Lagrangian. This allows for easier mathematical calculations and does not change the physical content of the statements. In gravity, the use of harmonic gauge serves a similar purpose.
  • #1
Neitrino
137
0
Hi...
Would you please advise me what does gauge fixing term do (physical point of view) ?

Does it eliminate unnecessary spin components from lagrangian for example:
Vector particle has two (massless case) or three (massive case) degrees of freedom.

Vector itself has four, and a vector (four component object) can handle spin-0 and spin 1 mode so adding a gauge fixing term does it project out spin-0 component ?

Or absence of spin-0 part is due to specific choice of kinetic term (F_mu_nu)...

Similarly in gravity... summetric tensor has 10 independent components and it can handle spin-0 spin-1 spin-2 modes... so does employment of harmonic gauge eliminate unnecessary modes or what role has it in this business?

Thanks
 
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  • #2
Hi neitrino,
The point of a gauge symmetry is that there's a redundancy in our description of the system; so physically, choosing a gauge is meaningless! The point is that you firstly have to choose some gauge, in order to actually write anything down at all, so you might as well pick one that makes the maths easy.
I can't say I'm familiar with harmonic gauge in GR, but having quickly looked it up the essential point seems to be the same; it doesn't alter the physical content of our statements, and it makes the maths easier in some problems- particularly when working in the weak-field approximation when we want to make contact between GR and Newtonian gravity.
 

What is a gauge fixing term?

A gauge fixing term is a mathematical expression used in the field of theoretical physics to remove certain degrees of freedom from a system. It is often used in quantum field theory to simplify calculations and make the results more physically meaningful.

What are the physical effects of a gauge fixing term?

The main physical effect of a gauge fixing term is to remove unphysical solutions from a system. These solutions can arise due to the presence of redundant degrees of freedom, and by fixing the gauge, we can obtain a more physically relevant description of the system.

Why is a gauge fixing term important in spin components?

In the context of spin components, a gauge fixing term is important because it allows us to remove unphysical states from the description of spin. This is particularly useful in theories involving gauge fields, where the presence of unphysical states can lead to inconsistencies in the theory.

How does a gauge fixing term affect the spin of a particle?

A gauge fixing term does not directly affect the spin of a particle. Instead, it affects the way we describe the spin and removes unphysical states from the theory. The physical spin of a particle remains unchanged.

Can a gauge fixing term be applied to all physical systems?

No, a gauge fixing term is only applicable to systems that exhibit gauge symmetry. This includes many physical systems, such as electromagnetic and weak interactions, but not all systems. In systems without gauge symmetry, a different approach must be used to remove unphysical states.

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