Covariant and contravariat components

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SUMMARY

The discussion centers on the confusion surrounding the representation of vectors using covariant and contravariant components, specifically the equation $$v=\sum_{i=0} e_i v^i$$ and its alternative form $$v=\sum_{i=0} e_i e^i v$$. The participant mistakenly equated the two forms, leading to the erroneous conclusion that $$v=3v$$ or $$v=5v$$. A clarification was provided, emphasizing the importance of correctly writing out inner products to avoid such mistakes, specifically distinguishing between $$\vec e_i (\vec e^i \cdot \vec v)$$ and $$(\vec e_i \cdot \vec e^i)\vec v$$.

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  • Understanding of vector notation and operations
  • Familiarity with covariant and contravariant components
  • Knowledge of inner product definitions in vector spaces
  • Basic principles of linear algebra
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mertcan
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hi, Initially I would like to ask a little and basic question: I know that $$v=\sum_{i=0} e_i v^i$$ where $$v^i=e^i v$$ But sometimes I think we can write the first equation like $$v=\sum_{i=0} e_i e^i v$$, and I am aware that $$e_i e^i=1$$ , then our equation becomes $$v=\sum_{i=0} v$$, ın short if we take the sum over i at the end, our equation becomes v=3v or v=5v...Could you help me get over this confusion I have sometimes in my mind? Very thanks in advance...
 
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You really should start writing out your inner products or you will keep making mistakes like this. What appears in your third sum is not ##(\vec e_i \cdot \vec e^i)\vec v##, it is ##\vec e_i (\vec e^i \cdot \vec v)##.
 
ok I got it I managed to ensure the derivation myself. Thanks...
 

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