תאריך:
ג', 10/01/202318:00-19:00
מיקום:
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I’ll discuss Federer's characterization of finite perimeter sets, and a new lemma on Hausdorff content, which is related to it. This lemma gives new information on Hausdorff content, and can be used to obtain other well-known results, such as the mass transference principle of Beresnevich and Velani. The lemma states precisely the following fact: If a collection of balls satisfies, in a scale invariant way, a lower bound for the Hausdorff content of its union, then it also satisfies a lower bound for the Hausdorff content on its limit superior set. The union is in general much larger than the limit superior set, and thus this result is nontrivial. I will seek to explain the statement, and how it relates to the two results mentioned.