Evaluating if a Vector is a Tensor

In summary, the problem is to determine if the four-component object (1/A^0, 1/A^1, 1/A^2, 1/A^3) is a tensor. Using the transformation rules for tensors of rank 1, we can write the object as (1/(dx^0/dx'^b * A'^b), 1/(dx^1/dx'^b * A'^b), 1/(dx^2/dx'^b * A'^b), 1/(dx^3/dx'^b * A'^b)). The next step is to try and transform the object to another frame and see if it follows the same rules, or if it cannot be fit into one of
  • #1
Libra82
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Homework Statement


Problem as stated: Consider a vector [itex]A^a[/itex]. Is the four-component object [itex]\left( \frac{1}{A^0},\frac{1}{A^1},\frac{1}{A^2},\frac{1}{A^3}\right)[/itex] a tensor?


Homework Equations


Roman indices run from 0 to 3. Einstein summation convention is used.
Tensors of rank 1 (vectors) transform as
Contravariant vectors: [itex] A^a = \frac{\partial x^a}{\partial x ' ^b}A'^b [/itex]
Covariant vectors: [itex] A_a = \frac{\partial x'^b}{\partial x^a}A'_b [/itex]


The Attempt at a Solution


I use the above mentioned transformation rules for each of the individual components getting:
[itex]\left( \frac{1}{A^0},\frac{1}{A^1},\frac{1}{A^2},\frac{1}{A^3}\right) = \left(\frac{1}{\frac{\partial x^0}{\partial x'^b}A'^b},\frac{1}{\frac{\partial x^1}{\partial x'^b}A'^b},\frac{1}{\frac{\partial x^2}{\partial x'^b}A'^b},\frac{1}{\frac{\partial x^3}{\partial x'^b}A'^b}\right)[/itex]

What I wanted was to transform the object to another frame and either arriving at a transformed object according to the above mentioned rules (confirming it is a tensor) or being unable to fit it into one of the rules above (disproving the object to be a tensor).

I am currently stuck with how to proceed.
 
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  • #2
Presumably all of those Aa are non-zero, and hence 1/Aa is bounded.

Hint: Certainly you can find a transformation that sets one of the coefficients of A' to zero.
 

FAQ: Evaluating if a Vector is a Tensor

1. What is a vector?

A vector is a mathematical object that has both magnitude and direction. It is commonly represented as an arrow pointing in a specific direction with a specific length.

2. What is a tensor?

A tensor is a mathematical object that describes linear relationships between vectors and other tensors. It can have multiple dimensions and is used in various fields of science, including physics, engineering, and machine learning.

3. How do you evaluate if a vector is a tensor?

To evaluate if a vector is a tensor, you need to check if it follows the properties of a tensor, which include linearity and transformation under change of basis. You also need to see if it can be described by a set of components that transform in a specific way under coordinate transformations.

4. What are the properties of a tensor?

The properties of a tensor include linearity, which means it follows the rules of addition and multiplication by a scalar, and transformation under change of basis, which means it can be described by a set of components that transform in a specific way under coordinate transformations.

5. How are tensors used in science?

Tensors are used in various fields of science, including physics, engineering, and machine learning. They are used to describe the physical properties of objects, such as stress, strain, and fluid flow. In machine learning, tensors are used to represent data and perform operations on it, such as image recognition and natural language processing.

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