How to prove that cuboids are Lebesgue measurable?

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In summary, to prove that cuboids are measurable in the context of the Lebesgue measure, one can start with the definition of measure for an interval being equal to its length. Since a cuboid is just the 3D analog of an interval, measure equals volume can be used as well. Alternatively, 3 space can be defined as the direct product of 3 lines and expanded from there. The challenge arises when the cuboid is rotated, but this is not part of the construction of the measure. One must still prove that the measure is invariant under rotations. Additional resources such as "Lebesgue measure lecture notes" can be found on Google for further assistance.
  • #1
Maxi1995
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Hello,
how do I have to start to prove that cuboids are measurable in the context of the Lebesgue measure?
Best wishes
Maxi
 
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  • #2
Measure theory starts from the definition of measure of an interval is equal to its length. A cuboid is just the 3d analog of an interval. You can start with measure equals volume or you can define 3 space as the direct product of 3 lines and go on from there.
 
  • #3
mathman said:
Measure theory starts from the definition of measure of an interval is equal to its length. A cuboid is just the 3d analog of an interval. You can start with measure equals volume or you can define 3 space as the direct product of 3 lines and go on from there.
I think the subtlety comes when the cuboid is rotated.
 
  • #4
The coordinate system can be rotated with it.
 
  • #5
mathman said:
The coordinate system can be rotated with it.
Yes, but that is not part of the construction of the measure. One still needs to prove that it is invariant under rotations.
 
  • #6
Gooogle "Lebesgue measure lecture notes" - this will get you more answers.
 
  • #7
Thank you for yor answers, I'm going to think about it and give a sign in case of further needed help. :)
 

Related to How to prove that cuboids are Lebesgue measurable?

1. How do you define a cuboid in mathematics?

A cuboid is a three-dimensional geometric shape with six rectangular faces. It is also known as a rectangular prism.

2. What does it mean for a cuboid to be Lebesgue measurable?

A cuboid is considered Lebesgue measurable if its volume can be accurately measured using the Lebesgue measure, which is a mathematical tool used to measure the sizes of sets in n-dimensional space.

3. How can you prove that a cuboid is Lebesgue measurable?

To prove that a cuboid is Lebesgue measurable, one must show that the volume of the cuboid can be accurately measured using the Lebesgue measure. This can be done by dividing the cuboid into smaller measurable units and summing their volumes using the Lebesgue measure.

4. What are the properties of Lebesgue measurable cuboids?

Lebesgue measurable cuboids have the property of being able to be divided into smaller measurable units, and their volume can be accurately measured using the Lebesgue measure. They also have a well-defined surface area, which can be calculated using the Lebesgue measure.

5. Are all cuboids Lebesgue measurable?

No, not all cuboids are Lebesgue measurable. A cuboid must have a well-defined volume and surface area in order to be considered Lebesgue measurable. If the cuboid is infinitely large or has a fractal surface, it may not be possible to accurately measure its volume or surface area using the Lebesgue measure.

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