What Are Tensors and Why Are They Important in Physics?

  • Context: Graduate 
  • Thread starter Thread starter 7777777
  • Start date Start date
  • Tags Tags
    Tensor
Click For Summary

Discussion Overview

The discussion revolves around the nature of tensors, their relationship to vectors, and their significance in physics, particularly in the context of general relativity. Participants explore definitions, mathematical properties, and the necessity of tensors in physical theories.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants express skepticism about the necessity of tensors, questioning whether they can be managed without them, while others argue that tensors simplify calculations significantly.
  • There is a contention regarding the fundamental nature of vectors versus tensors, with some asserting that vectors are more fundamental, while others clarify that vectors are a specific type of tensor.
  • Participants discuss the mathematical definitions of tensors and vectors, with some emphasizing that tensors satisfy the requirements of a vector space, while others argue that not all vectors qualify as tensors.
  • Several participants mention the importance of the metric tensor in operations involving vectors and tensors, noting that it is trivial in Cartesian coordinates.
  • Some contributions highlight the need for a deeper understanding of linear algebra to grasp tensors better, suggesting that traditional learning methods may be outdated.
  • There is a discussion about the representation of tensors, vectors, and scalars as arrays of different dimensions, with some participants emphasizing the coordinate-free nature of tensors.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the fundamental nature of tensors versus vectors, and there are multiple competing views regarding the necessity and definition of tensors in physics and mathematics.

Contextual Notes

Some participants note that their understanding of tensors is influenced by specific educational approaches, which may vary significantly. There is also mention of the dependence on coordinate systems for the representation of tensors.

  • #31
PSarkar said:
But then how is the definition coordinate free? You are forced to choose some coordinates in order to work with tensors.

This depends on what you mean by "work" and in what context but the definition is clearly coordinate-free. I would suggest you take a look at Roman's linear algebra text.
 
Physics news on Phys.org
  • #32
Will be the Laplacian, \bigtriangledown ^2, in actually, a Tensor?? Will be a simplification of Hessian tensor?
 
  • #33
Come think in 2D. Given 2 values, a and b, it's possible to associate a point P with coordinates (a, b) and trace a straight between the origem and the point P. Ready, we have a vector! So, analogously, given 4 values (a, b, c, d), should be possible to associate these values with straight, and, somehow associate a plane with this straight. This, geometrically, would be a tensor. I think...
 
  • #34
WannabeNewton said:
This depends on what you mean by "work" and in what context but the definition is clearly coordinate-free. I would suggest you take a look at Roman's linear algebra text.

Can you explain why the multilinear array definition is coordinate free as this is not obvious to me. If you need to choose coordinates to get the tensor, then the tensor depends on which coordinates you choose. You definitely cannot write one down without choosing coordinates. This definition misses the essence of tensor which is independent of any coordinate and so we should have a definition and representation without coordinates.

I think jgens answer about collecting all the coordinate representation of the tensors together make sense since it will no longer depend on the coordinates. But the down side is you still can't write one down without coordinates.
 
  • #35
PSarkar said:
Can you explain why the multilinear array definition is coordinate free as this is not obvious to me.

Sorry when you said "the definition" I thought you were referring to the usual algebraic definition of a tensor as this is what I take to be "the definition" of a tensor. I find it hard to look at anything relying on coordinate representations as a definition hence I agree that a definition in terms of coordinate components is archaic and inferior for the reasons stated by you and others.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 26 ·
Replies
26
Views
3K
  • · Replies 4 ·
Replies
4
Views
4K