Levi-Civita symbol for cross products?

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Discussion Overview

The discussion revolves around the use of the Levi-Civita symbol for calculating cross products, specifically in the context of expressions like A x (B x C). Participants explore the efficiency of this method compared to traditional determinant approaches, considering the learning curve and practical application in physics problems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether using the Levi-Civita symbol is faster than the determinant method for calculating cross products, citing a personal experience of difficulty with the method.
  • Another participant asserts that learning the Levi-Civita symbol is beneficial and encourages practice, suggesting that it will become easier over time.
  • A third participant mentions specific properties of the Levi-Civita symbol, indicating that understanding these properties can simplify calculations and make the method more efficient.
  • One participant contrasts the use of the Levi-Civita symbol for A x (B x C) with its application in A ⋅ (B x C), noting that the two methods yield the same result under certain conditions, but emphasizes that the choice of method depends on the algorithm used for calculations.

Areas of Agreement / Disagreement

Participants express differing views on the efficiency and practicality of using the Levi-Civita symbol versus traditional methods. While some advocate for the symbol's advantages, others remain uncertain about its immediate utility and efficiency.

Contextual Notes

The discussion highlights a learning curve associated with the Levi-Civita symbol and its properties, as well as the potential complexity of calculations involved in triple products. There is no consensus on which method is superior, and participants present varying perspectives on the effort required to learn the Levi-Civita approach.

Who May Find This Useful

This discussion may be of interest to students and practitioners in physics and engineering who are exploring different methods for vector calculations, particularly in the context of electromagnetism and advanced mechanics.

Nikitin
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Hi. Is using the Levi-Civita symbol to calculate cross-product combos like A x (B x C) allot faster than just using the good old determinant method?

I ask because my lecturer in electrodynamics 2 told us it is better, but it seems to me that it's going to cost me time to learn to use this method efficiently (it took me over 20 minutes to do a triple cross product with it!). Will the pay-off be worth the practice?
 
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It may not seem useful to you right now, but it really is. Try to learn it.
 
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Once you've learned how to handle ##\varepsilon_{ijk}\varepsilon_{ijl}## and ##\varepsilon_{ijk}\varepsilon_{ilm}##, and that if ##S_{jk}=S_{kj}## then ##\varepsilon_{ijk}S_{jk}=0##, you will find it much easier to work with the Levi-Civita symbol than any other method. It's definitely worth the effort. It's not a very big effort, since those three things I mentioned are the only basic results you need to know.
 
Not sure about A × (B × C), but for A ⋅ (B × C) 3-dimensional Levi-Civita symbol with its 6 non-zero components, if used once as εijkAiBjCk, and (expanded) formula for rank-3 determinant, are the same thing.

As a general remark, not Levi-Civita vs matrix methods makes the difference, but now exactly the algorithm arranges calculation of the cubic polynomial(s) on components for given type of triple product.
 
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