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A Gentle Introduction to Tensors (2014) [pdf]

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Re: A Gentle Introduction to Tensors (2014) [pdf]

#11
post #7

Yet to see a "Gentle Introduction to" that didn't freely and accurately translate to poorly written, impenetrable prose whose purpose is to gratify the ego of the author in demonstrating how they are unbelievably more clever than any reader who could conceivably require any kind of "introduction" Is that bad luck on my part? (I've given up on thinking I'm particularly or especially dense - while making no claims to b…

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Re: A Gentle Introduction to Tensors (2014) [pdf]

#12
post #7

Yet to see a "Gentle Introduction to" that didn't freely and accurately translate to poorly written, impenetrable prose whose purpose is to gratify the ego of the author in demonstrating how they are unbelievably more clever than any reader who could conceivably require any kind of "introduction" Is that bad luck on my part? (I've given up on thinking I'm particularly or especially dense - while making no claims to b…

How should it have been done. Tensors are pretty complicated. It's like advanced calc plus advanced linear algebra. Maybe watch dome youtube videos on general relativity. Those are sometimes better than texts because clarity is essential.

Re: A Gentle Introduction to Tensors (2014) [pdf]

#13
post #2

I have always hated when tensors are defined as something whose coordinates are transformed in a certain way. I just find it inherently unfriendly and un-geometric. No matter how much talk is given about simpler cases such as scalars, vectors, covectors, etc., the final defining formula would still look to me as daunting as always. (There is nothing “gentle” about the formulas on page 14.) Surprisingly or not, the wh…

Could you recommend a text/paper/blog article which develops tensor theory from an algebraic setting?

Re: A Gentle Introduction to Tensors (2014) [pdf]

#14
post #2

I have always hated when tensors are defined as something whose coordinates are transformed in a certain way. I just find it inherently unfriendly and un-geometric. No matter how much talk is given about simpler cases such as scalars, vectors, covectors, etc., the final defining formula would still look to me as daunting as always. (There is nothing “gentle” about the formulas on page 14.) Surprisingly or not, the wh…

Could you recommend a text/paper/blog article which develops tensor theory from an algebraic setting?

Chapter 12 of this book https://math.berkeley.edu/~jchaidez/materials/reu/lee_smooth...

Re: A Gentle Introduction to Tensors (2014) [pdf]

#15
post #2

I have always hated when tensors are defined as something whose coordinates are transformed in a certain way. I just find it inherently unfriendly and un-geometric. No matter how much talk is given about simpler cases such as scalars, vectors, covectors, etc., the final defining formula would still look to me as daunting as always. (There is nothing “gentle” about the formulas on page 14.) Surprisingly or not, the wh…

Could you recommend a text/paper/blog article which develops tensor theory from an algebraic setting?

Hm, that’s a good question! Pretty much any modern book on, or with a chapter on, multilinear algebra, or even a text with a modern treatment of differential geometry (smooth manifolds) would, I imagine, do a decent job. Also, searching the web for “tensors as multilinear forms” turns up quite a few promising links. For a video lecture that could give you a flavor of what tensors are from the linear-algebraic perspective, try

https://www.youtube.com/watch?v=4l-qzZOZt50

(You might get more mileage if you also watch the preceding lecture(s) of this excellent series.)

Re: A Gentle Introduction to Tensors (2014) [pdf]

#17
Argh! People make this so much more complicated than it has to be.

A tensor of rank N is a vector in a space whose basis is a set of N-tuples of ordinary vectors. That's it. So a rank-1 tensor is just a regular vector. A rank-2 tensor is a vector in a space whose basis is ordered pairs of regular vectors, a rank-3 tensor is a vector in a space whose basis is ordered triples of regular vectors, and so on.

Re: A Gentle Introduction to Tensors (2014) [pdf]

#19
An easy to read (minimal theorems) but authoritative and modern introduction to tensors can be found in the book “An Introduction to Tensors and Group Theory for Physicists” by Jevanjee (https://www.springer.com/gp/book/9783319147932).

He takes the more geometrical perspective as a tensor as a multi-linear function of vectors, from which all other statements about tensors (eg how the components transform) follows straightforwardly. Lots of other great material in this book and best of all there are loads of examples.

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