Divergence and Curl: Can a Non-Constant Function Have Both 0?

In summary, a non-constant function can have both 0 divergence and 0 curl, meaning it is irrotational and incompressible. This can be achieved when the partial derivatives of the function with respect to all three spatial coordinates are equal to 0. Such functions have physical significance in fluid mechanics and electromagnetism. However, they cannot exist in three-dimensional space, according to the Helmholtz decomposition theorem. Real-life applications of functions with 0 divergence and 0 curl include modeling potential flows and electrostatic and magnetostatic fields.
  • #1
ehrenfest
2,020
1
I am trying to think of a non-constant function whose divergence and curl is 0. It seems like this is impossible to me. Any hints?
 
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  • #2
Well, if the curl is zero, you can write the field as a gradient of some scalar function. So, if the divergence is also zero, what does that tell you? (Hint: Laplace equation)
 
  • #3
Potential theory would be dreadfully boring to study if the Laplace equation had only constant solutions..
 

1. Can a non-constant function have both 0 divergence and 0 curl?

Yes, it is possible for a non-constant function to have both 0 divergence and 0 curl. This means that the function is both irrotational and incompressible, which is often referred to as a solenoidal vector field.

2. How can a function have 0 divergence and 0 curl?

A function can have 0 divergence and 0 curl if its partial derivatives with respect to all three spatial coordinates are equal to 0. This means that the function is not changing or rotating in any direction, resulting in a constant magnitude and direction at every point.

3. Does a function with 0 divergence and 0 curl have any physical significance?

Yes, a function with 0 divergence and 0 curl has physical significance in fluid mechanics and electromagnetism. In fluid mechanics, such a function represents a flow that is both incompressible and irrotational, while in electromagnetism it represents a vector field with no sources or sinks and no circulation.

4. Can a function with 0 divergence and 0 curl exist in three-dimensional space?

No, a function with 0 divergence and 0 curl cannot exist in three-dimensional space. This is because in three dimensions, a function with 0 divergence must have a non-zero curl, and vice versa. This is known as the Helmholtz decomposition theorem.

5. Are there any real-life applications of functions with 0 divergence and 0 curl?

Yes, there are several real-life applications of functions with 0 divergence and 0 curl. For example, in fluid mechanics, these functions are used to model potential flows, which are idealized flows that are both incompressible and irrotational. In electromagnetism, these functions are used to model electrostatic and magnetostatic fields, where there are no sources or sinks of electric charge or magnetic field.

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