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Also: Cross products.


I'm sure it's out there somewhere, but it would be an appropriate corollary to the OP if there was a "Down with Cross Products", which argues that multivectors and wedge products should be taught instead of cross products in multivariable calculus. Then, determinants are "the wedge product of N linearly independent vectors", and cross products are "the wedge product of 2 vectors in 3 dimensions", which gives a bivector and trivially encodes their pseudovector properties.

(Also, surface normals in integrals are bivectors, the 'i' of complex analysis is the bivector resulting from wedge product x^y, and e^(i theta) is the exponential map applied to the i operator, and (del wedge vector-function f) is the (bivector-valued) curl while (del wedge bivector-function g) is the (scalar valued) divergence (and that's why del(del(f)) = 0).)

(But differential forms should probably be omitted in a first course, because they get hairy quickly and are hard to wrap one's head around. It's enough to know that dxdy in integrals is actually dx^dy, and therefore the Jacobian appears when changing variables because of the factor that appears from dx'^dy' = dx'(x,y)^dy'(x,y).)


Which books would you recommend to learn this wedge product / differential forms approach to linear algebra and complex numbers?


Doesn't Spivak get into them?


Michael Spivak has written multiple books. Which one do you mean?


Calculus on Manifolds. I'd recommend Hubbard and Hubbard over that as it's a little easier read with the same material.


> I'd recommend Hubbard and Hubbard over that as it's a little easier read with the same material.

John Hamal Hubbard, Barbara Burke Hubbard - Vector Calculus, Linear Algebra and Differential Forms: A Unified Approach


Based on this article, I would venture to guess that Axler is also not a fan of the cross product, though, so he wouldn't feel that much is lost. Cross products are practically a vector-calculus hack that lack generality and risk obscuring intuition at the mathematical level.


One problem with cross product, it only exists in three dimensions.


No, it exists in dimension 3 and 7:

> https://en.wikipedia.org/wiki/Seven-dimensional_cross_produc...

EDIT: Nore precisely: A common way to axiomatize the cross product yields a cross products exactly in dimension 3 and 7.


A wedge product exists in all dimensions but only in 3 & 7 is it identifiable with a unique vector.




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