Can the cross product concept be completely replaced by the exterior product?

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Discussion Overview

The discussion centers on the relationship between the cross product and the exterior product, particularly whether the cross product can be entirely replaced by the exterior product in mathematical and physical contexts. The scope includes theoretical considerations and conceptual clarifications regarding their definitions and applications in different dimensions.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that the cross product is a simplification of the exterior product tailored for three-dimensional space, questioning its necessity.
  • Others argue that the cross product can be replaced by the exterior product if done correctly, although it may not simplify physics formulas.
  • One participant notes that the exterior product and cross product share the same coordinates in R^3, highlighting their connection through determinants and their alternating, multilinear properties.
  • Another participant references Wikipedia to illustrate the relationship between the cross product and the wedge product, indicating a formal definition that links the two concepts.
  • Some advocate for the exterior product's use in Geometric Algebra, acknowledging a learning curve but suggesting it offers significant simplifications.

Areas of Agreement / Disagreement

Participants express differing views on whether the cross product can be completely replaced by the exterior product, with no consensus reached on the implications for simplifying physics formulas.

Contextual Notes

Participants acknowledge that the cross product is specific to three dimensions, while the exterior product applies to spaces of any dimension. The discussion also touches on the complexities involved in transitioning from one concept to the other.

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Do we really need concept of cross product at all? I always believed cross product to be sort of simplification of exterior product concept tailored for the 3D case. However, recently I encountered the following sentence «...but, unlike the cross product, the exterior product is associative». (https://en.wikipedia.org/wiki/Exterior_algebra) and it occurred to me that I might have been missing something.

Two remarks:
1) Clearly cross product is tied to 3D world and exterior product works for space of any dimension. Suppose we are considering 3D case only.
2) The cross product can be convenient tool. Being such it has every right to exist. But I am asking about whether it could be dropped entirely in favour of its exterior counterpart without losing anything in principle.
 
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if you write down the definition of the exterior product of two vectors in R^3, you will see that it has the same coordinates as their cross product. However if e1,e2,e3 is the standard basis of R^3, the cross product will be expanded in terms of that same basis, while the exterior product will be expanded in the basis e2^e3, e3^e1, e2^e3. The point is that both are aspects of the determinant, in particular both products are "alternating" and multilinear, and the only determinant is essentially the only such product.
 
wrobel said:
Yes, cross product concept can be replaced with exterior product provided one does it correctly. But it would hardly simplify physics formulas
https://en.m.wikipedia.org/wiki/Hodge_star_operator
The exterior product is preferred in Geometric Algebra. Although there is a significant learning curve, GA is considered by its advocates to offer great simplifications.
 

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