Changing Dot Product to Simple Multiplication

In summary, to change the dot product so that there is no dot product in between, one would need to know further information, such as the components of the metric tensor, in order to get an expression for the partial derivative of the coordinate basis vector. The \Gamma 's can then be represented in terms of these partial spatial derivatives.
  • #1
Halaaku
23
0
How does one change the dot product such that there is no dot product in between, just plain multiplication? For example, in the following:
eb.[itex]\partial[/itex]cea=-[itex]\Gamma[/itex]a bc

How do I get just an expression for [itex]\partial[/itex]cea?
 
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  • #2
Here [itex]\Gamma[/itex]a bc = ea.∂ceb
 
  • #3
I have no knowledge of the particular symbols. However if you have the dot product of two vectors equal to a scalar, you cannot get one of the vectors from the scalar without further information. It is not enough just to know the other vector.
 
  • #4
Halaaku said:
Here [itex]\Gamma[/itex]a bc = ea.∂ceb

The partial derivative of the coordinate basis vector eb with respect to the spatial coordinate xc is a vector, which can be expressed at a given point as a linear combination of the coordinate basis vectors:

[tex]\frac{\partial e_b}{\partial x^c}=\Gamma^j_{bc}e_j[/tex]

The [itex]\Gamma 's[/itex] are the components of the vector. If we dot this equation with the duel basis vector ea, we get:
[tex]e^a\centerdot\frac{\partial e_b}{\partial x^c}=\Gamma^a_{bc}[/tex]

The trick is to figure out how to represent the [itex]\Gamma 's[/itex] in terms of the partial spatial derivatives of the components of the metric tensor.
 
  • #5


To change the dot product to simple multiplication, you would need to remove the dot product symbol (·) and replace it with the multiplication symbol (×) between the two vectors or matrices. This would result in a multiplication of the individual elements instead of a scalar product.

In the given example, to get an expression for \partialcea, you would simply multiply the vectors eb and -\Gammaa bc, resulting in:

\partialcea = -eb × \Gammaa bc
 

FAQ: Changing Dot Product to Simple Multiplication

What is the difference between dot product and simple multiplication?

The dot product is a mathematical operation that takes two vectors as input and returns a scalar value. It is a way to measure the similarity or projection of one vector onto another. Simple multiplication, on the other hand, is a basic arithmetic operation that involves multiplying two or more numbers together.

2. Why would you want to change a dot product to simple multiplication?

There are various reasons why one might want to change a dot product to simple multiplication. For example, if the two vectors being multiplied have a specific property, such as being orthogonal (perpendicular), then the dot product will be equal to zero and can be replaced by simple multiplication. This can make calculations more efficient and easier to interpret.

3. Can the dot product always be changed to simple multiplication?

No, the dot product cannot always be changed to simple multiplication. This is because the dot product takes into account both the magnitude and direction of the vectors, while simple multiplication only considers their magnitudes. If the direction of the vectors is important for the calculation, then the dot product cannot be replaced.

4. Are there any disadvantages to changing a dot product to simple multiplication?

Yes, there can be disadvantages to changing a dot product to simple multiplication. As mentioned before, the dot product takes into account the direction of the vectors, which can be important in certain calculations. By replacing the dot product with simple multiplication, the direction information is lost and the resulting calculation may not be as accurate.

5. How do you change a dot product to simple multiplication?

The process of changing a dot product to simple multiplication depends on the specific problem at hand. In general, you can look for any properties of the vectors that can simplify the dot product, such as orthogonality, and then use basic algebraic manipulations to replace the dot product with simple multiplication. It is important to consider the implications of this change and ensure that it does not affect the accuracy of the calculation.

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