Order of Operations for Tensors

In summary, the conversation discusses the simplification of ν∇⋅(ρν) where ν is a vector, ∇ is the "del operator", ⋅ indicates a dot product, and ρ is a constant. The conversation suggests using the dyadic product of ν and ∇, but notes that this would result in meaningless terms. It is then suggested to perform the dot product first, but the order of operations for algebra involving tensors is unclear. The conversation then references a product rule for vector calculus that simplifies the expression to a scalar, and notes that multiplying ν by this scalar would give a vector.
  • #1
echandler
21
1
Hey so probably a really simple question, but I'm stumped. How do you simplify:

ν∇⋅(ρν), where
ν is a vector
∇ is the "del operator"
⋅ indicates a dot product
ρ is a constant.

I want to say to do the dyadic product of v and ∇, but then you would get (v_x)*(d/dx) + ... which would be meaningless, so I'm thinking you do the dot product first, but I can't find an order of operations for algebra involving tensors of any order (except zero order of course).

Thanks in advance.
 
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  • #2
It's kind of like a product rule for vector calculus:
$$\nabla \cdot (\rho \vec{\nu}) = \rho \nabla \cdot \vec{\nu} + \vec{\nu} \cdot \nabla \rho$$
gives you a scalar. ##\vec{\nu} \nabla \cdot (\rho \vec{\nu}) ## just multiplies the vector ##\vec{\nu}## by that scalar.
 

1. What is the purpose of using the order of operations for tensors?

The order of operations for tensors helps to ensure that calculations involving tensors are carried out in a consistent and accurate manner. It also helps to prevent errors and confusion when working with complex mathematical expressions.

2. What are the basic rules for the order of operations for tensors?

The basic rules for the order of operations for tensors are similar to those for regular algebraic expressions. The operations are performed in the following order: parentheses, exponents, multiplication and division (from left to right), and finally addition and subtraction (from left to right).

3. How does the order of operations for tensors differ from regular algebraic expressions?

The main difference is that tensors have multiple dimensions, whereas regular algebraic expressions only have one. This means that operations must be performed in a specific order to account for the different dimensions and prevent errors.

4. Can the order of operations for tensors be changed?

No, the order of operations for tensors is fixed and cannot be changed. This is because it is based on the properties and mathematical rules of tensors, and altering the order could result in incorrect calculations.

5. What are some common mistakes to avoid when using the order of operations for tensors?

Some common mistakes to avoid include not accounting for the dimensions of tensors, not following the correct order of operations, and forgetting to use parentheses when necessary. It is also important to double check calculations and refer to the specific rules for tensors if needed.

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