What does the total time derivative of a function signify in Noether's Theorem?

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SUMMARY

The total time derivative of a function in Noether's Theorem signifies a transformation that maintains the invariance of the action, which is crucial for deriving conserved quantities in physics. The discussion emphasizes that while the Lagrangian can change under infinitesimal transformations, the addition of a total time derivative does not affect the equations of motion. Participants suggest calculating conserved quantities for specific examples to better understand the physical interpretation of this derivative.

PREREQUISITES
  • Understanding of Noether's Theorem
  • Familiarity with Lagrangian mechanics
  • Basic calculus concepts, particularly derivatives
  • Knowledge of infinitesimal transformations
NEXT STEPS
  • Explore the implications of Noether's Theorem in classical mechanics
  • Calculate conserved quantities for specific Lagrangians
  • Investigate the role of total time derivatives in field theory
  • Study examples of infinitesimal transformations in physics
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Physicists, students of theoretical mechanics, and anyone interested in the applications of Noether's Theorem in understanding conservation laws in physics.

Higgsono
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We can look at infinitesimal transformations in the fields that leaves the Lagrangian invariant, because that implies that the equations of motions are invariant under this transformations. But what really matters is the those transformations that leaves the action invariant. So we can always add a total time derivative of a functions such that the change in the Lagrangian under a infinitesimal transformation is proportional to a total time derivative of a function.

My question is, what is the physical interpretation of this? What does this total time derivative of a function represent?
 
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Higgsono said:
What does this total time derivative of a function represent?

You must have some calculus education, so that really can't be your question, can it?
 
Higgsono said:
So we can always add a total time derivative of a functions such that the change in the Lagrangian under a infinitesimal transformation is proportional to a total time derivative of a function.
That is an interesting idea. I don’t know what such a quantity would represent in general. Perhaps you should calculate the corresponding conserved quantity for a few specific examples to gain insight.
 

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