# Tensor notation Definition and 11 Discussions

This is a glossary of tensor theory. For expositions of tensor theory from different points of view, see:

Tensor
Tensor (intrinsic definition)
Application of tensor theory in engineering scienceFor some history of the abstract theory see also Multilinear algebra.

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1. ### B Array Representation Of A General Tensor Question

So, I've been watching eigenchris's video series "Tensors for Beginners" on YouTube. I am currently on video 14. I, in the position of a complete beginner, am taking notes on it, and I just wanted to make sure I wasn't misinterpreting anything. At about 5:50, he states that "The array for Q is...
2. ### B Transformation Rules For A General Tensor M

So, I've been watching eigenchris's video series "Tensors for Beginners" on YouTube. I am currently on video 14. I am a complete beginner and just want some clarification on if I'm truly understanding the material. Basically, is everything below this correct? In summary of the derivation of the...
3. ### B Beginner Einstein Notation Question On Summation In Regards To Index

So, I have recently been trying to learn how to work with tensors. In doing this, I have come across Einstein Notation. Below is my question. $$(a_i x_i)_{e}= (\sum_{i=1}^3 a_i x_i)_r=(a_1 x_1+a_2 x_2+a_3 x_3)_r$$; note that the following expression is in three dimensions, and I use the...
4. ### I Usage of First Order Elastic Constants in Soft Body Equations

Hi, I have some soft body equations that require first order elasticity constants. Just trying to figure out the proper indexing. From Finite Elements of Nonlinear Continua by J.T. Oden, the elastic constants I am trying to obtain are the first order, circled below: My particular constitutive...
5. ### I Doubt about the purpose of some elements in tensor calculus

I would like to know what is the utility or purpose for which the elements below were defined in the Tensor Calculus. They are things that I think I understand how they work, but whose purpose I do not see clearly, so I would appreciate if someone could give me some clue about it. Tensors. As...
6. ### I Expressing the vectors of the dual basis with the metric tensor

I'm trying to understand why it is possible to express vectors ##\mathbf{e}^i## of the dual basis in terms of the vectors ##\mathbf{e}_j## of the original basis through the dual metric tensor ##g^{ij}##, and vice versa, in these ways: ##\mathbf{e}^i=g^{ij}\mathbf{e}_j##...
7. ### On the Validity of Swapping Dummy Indices in Tensor Manipulation

Property (a) simply states that a second rank tensor that vanishes in one frame vanishes in all frames related by rotations. I am supposed to prove: ##T_{i_1 i_2} - T_{i_2 i_1} = 0 \implies T_{i_1 i_2}' - T_{i_2 i_1}' = 0## Here's my solution. Consider, T_{i_1 i_2}' - T_{i_2 i_1}' = r_{i_1...
8. ### Lorentz gauge

hi, I'm currently taking a classical field theory class (electromagnetism in the language of tensors and actions and etc) and we have just encountered the gauge symmetry, that is for the 4 vector potential we can add a gradient of some smooth function and get the same physics (if we take Aμ →...
9. ### I How to sum the first term in the Maxwell field Lagrangian

So the first term of the Lagrangian is proportional to ##{F_{\mu \nu}}{F^{\mu \nu}}##. I wrote out the matrices for ##{F_{\mu \nu}}## and ##{F^{\mu \nu}}## and multiplied at the terms together and added them up, but some of the terms didn't cancel like they should have. Should I have used minus...
10. ### Help with tensor formulation of special relativity

Homework Statement Hi, I can't seem to understand the following formula in my professor's lecture notes: F_αβ = g_αγ*g_βδ*F^(γδ) Homework Equations Where g_αβ is the diagonal matrix in 4 dimensions with g_00 = 1 and g_11 = g_22 = g_33 = -1 and F^(γδ) is the electromagnetic tensor with c=1...
11. ### General pathline of a particle x at point epsilon at time ta

Homework Statement Show that the path line of a particle at point x currently, and point ξ at time τ is given by ξ(τ) = x + (τ-t)Lx Homework Equations Pathline is solution to dx/dt = u x(t)|t=τ = X L is the velocity gradient and is a 2nd order tensor Lij = dui/dxj The Attempt at a...