Extremal t-intersecting sub-families of hereditary families

摘要

A family 𒜠of sets is said to be t-intersecting if any two sets in 𒜠contain at least t common elements. A t-intersecting family is said to be trivial if there are at least t elements common to all its sets. A family ℋ is said to be hereditary if all subsets of any set in ℋ are in ℋ.