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Engineering LibreTexts

14.6: Summary

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  • In this chapter, a procedure to find continuous symmetries of equations was presented. Also, the relationship between continuous symmetries and invariants, known as Noether's theorem, was discussed. If we can describe an energy conversion process by a Lagrangian, we can use the techniques of calculus of variations detailed in Chapter 11 to find the equation of motion for the path. We can use the procedure discussed in this chapter to identify continuous symmetries of the equation of motion. These symmetry transformations are denoted by infinitesimal generators which describe how the independent and dependent variables transform. We also may be able to use Noether's theorem to find invariants of the system. We can apply this analysis even in cases where the equation of motion is nonlinear or has no closed form solution. The invariants often correspond to physical quantities, such as energy, momentum, or angular momentum, which are conserved in the system. Knowledge of invariants can help us gain insights into what quantities change and what quantities do not change during the energy conversion process under study