Reversing transformations of displacements

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SUMMARY

The discussion focuses on reversing transformations of displacements as outlined in Neuenschwander's Tensor Calculus for Physics. The user is attempting to derive the relationship between unprimed and primed coordinates using the equations x(x', y', z'), y(x', y', z'), z(x', y', z'), and their primed counterparts. A critical error identified is the incorrect assumption that the product of partial derivatives, specifically ##\frac{\partial x'}{\partial x}\frac{\partial x}{\partial x'}=1##, holds true, which is not guaranteed. The user is advised to compare their results with the fourth equation in the text that includes the Kronecker delta for accurate transformations.

PREREQUISITES
  • Understanding of tensor calculus concepts, particularly transformations of coordinates.
  • Familiarity with partial derivatives and their application in coordinate transformations.
  • Knowledge of the Kronecker delta and its role in tensor equations.
  • Basic proficiency in mathematical notation and manipulation of equations.
NEXT STEPS
  • Review the fourth equation in Neuenschwander's Tensor Calculus for Physics that involves the Kronecker delta.
  • Practice reversing transformations with simple coordinate systems to solidify understanding.
  • Explore the implications of non-linear transformations in tensor calculus.
  • Study the properties of partial derivatives in the context of coordinate transformations.
USEFUL FOR

Students self-studying tensor calculus, particularly those encountering challenges with coordinate transformations and their applications in physics.

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Homework Statement



I've just started (self-studying) Neuenschwander's Tensor Calculus for Physics and I got stuck at page 23, where he deals with transformations of displacements. I've made a summary of page 23 in the first part of the attached file.

Homework Equations



I want to use the coordinates x(x', y', z'), y(x', y', z'), z(x', y', z') and x'(x,y,z), y'(x,y,z), z'(x,y,z) and try to reverse the original transformation from unprimed to primed, see attached file.

The Attempt at a Solution


[/B]
I get a result which seems to say that dx'= 3dx', see attached file. So I don't understand where I'm going wrong. I'd be very grateful if anyone could help.
 

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beowulf.geata said:

Homework Statement



I've just started (self-studying) Neuenschwander's Tensor Calculus for Physics and I got stuck at page 23, where he deals with transformations of displacements. I've made a summary of page 23 in the first part of the attached file.

Homework Equations



I want to use the coordinates x(x', y', z'), y(x', y', z'), z(x', y', z') and x'(x,y,z), y'(x,y,z), z'(x,y,z) and try to reverse the original transformation from unprimed to primed, see attached file.

The Attempt at a Solution


[/B]
I get a result which seems to say that dx'= 3dx', see attached file. So I don't understand where I'm going wrong. I'd be very grateful if anyone could help.
Look carefully at the expression multiplying dx', and compare it with the fourth equation in your text, the one with the Kronecker delta.
You seem to assume that ##\frac{\partial x'}{\partial x}\frac{\partial x}{\partial x'}=1## and similarly for the other two terms. That is not necessarily the case.

You can test it with a simple transformation (for two dimensions):
##x'=x+y##
##y'=x-y##
 
Thanks very much! I now see the error of my ways :-)
 

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