Parametrizations of the 3-sphere

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Discussion Overview

The discussion revolves around the parametrizations of the 3-sphere, specifically examining two proposed sets of equations. Participants explore whether these parametrizations are equivalent and seek to understand the relationship between the parameters involved.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant presents two sets of parametrizations for the 3-sphere and questions their equivalence.
  • Another participant suggests verifying the condition \(x^2+y^2+z^2+w^2=1\) to check the validity of the parametrizations.
  • A participant confirms that the condition holds but expresses difficulty in finding a diffeomorphism between the two sets of parameters.
  • Further, a participant proposes renaming parameters in the second set and attempts to derive relationships between the parameters of the two sets, indicating a complex transformation process.

Areas of Agreement / Disagreement

Participants generally agree that both sets of parametrizations are valid, as confirmed by the mathematical check. However, there is no consensus on whether a diffeomorphism exists between them, and the discussion remains unresolved regarding the transformation between the two sets of parameters.

Contextual Notes

The discussion highlights the complexity of finding a transformation between the two parametrizations, with some expressions remaining unresolved and dependent on the definitions of the parameters.

jk22
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i got the 2 following parametrizations :
x=sin a sin b sin c
y=sin a sin b cos c
z=sin a cos b
w=cos a

And
x=sin a sin b
y=sin a cos b
z=cos a sin c
w=cos a cos c

Are those really 2 parametrizations of the 3-sphere and are they equivalent ?
Thanks.
 
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Just check x^2+y^2+z^2+w^2?

What do you mean with "equivalent"?
 
the check is ok. I mean there exist a diffeomorphism between them. But I couldn't find such a transformation between the two sets of parameters
 
Well, if I rename the second parameters to d,e,f:

x=sin a sin b sin c = sin d sin e
y=sin a sin b cos c = sin d cos e
z=sin a cos b = cos d sin f
w=cos a = cos d cos f

=>
a=acos(cos d cos f)
b=acos(cos d sin f / sin a) (where you can insert a here)
c = [even longer expression where you can insert b and a]
 

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