Sets of finite perimeter which do not contain any open ball
Some time ago, I wondered myself if I could find a very small ball included in a set of finite perimeter (see definition for set of finite perimeter here and here). It turns out, that the answer is no, there mustn’t be any open ball included in a set of finite perimeter. My teacher gave me the following nice example.
Example: Take , the unit ball in and denote
. Then, we can find a sequence of positive real numbers such that
Define .
Then has the desired property. Indeed, , and .
If would contain an open ball then that ball would intersect , which is not possible.
Categories: Geometry, shape optimization
shape optimization
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