A New Construction of Non-Extendable Intersecting Families of Sets
نویسنده
چکیده
In 1975, Lovász conjectured that any maximal intersecting family of k-sets has at most b(e− 1)k!c blocks, where e is the base of the natural logarithm. This conjecture was disproved in 1996 by Frankl and his co-authors. In this short note, we reprove the result of Frankl et al. using a vastly simplified construction of maximal intersecting families with many blocks. This construction yields a maximal intersecting family Gk of k-sets whose number of blocks is asymptotic to e(k2 ) k−1 as k →∞.
منابع مشابه
Regular bipartite graphs and intersecting families
In this paper we present a simple unifying approach to prove several statements about intersecting and cross-intersecting families, including the Erdős–Ko–Rado theorem, the Hilton–Milner theorem, a theorem due to Frankl concerning the size of intersecting families with bounded maximal degree, and versions of results on the sum of sizes of non-empty cross-intersecting families due to Frankl and ...
متن کاملCounting Intersecting and Pairs of Cross-Intersecting Families
A family of subsets of {1, . . . , n} is called intersecting if any two of its sets intersect. A classical result in extremal combinatorics due to Erdős, Ko, and Rado determines the maximum size of an intersecting family of k-subsets of {1, . . . , n}. In this paper we study the following problem: how many intersecting families of k-subsets of {1, . . . , n} are there? Improving a result of Bal...
متن کاملExtremal t-intersecting sub-families of hereditary families
A family A of sets is said to be t-intersecting if any two sets in A 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. For a finite family F , let F (s) be the family of s-element sets in F , and let μ(F) be the size of a smallest ...
متن کاملNon-trivial intersecting uniform sub-families of hereditary families
For a family F of sets, let μ(F) denote the size of a smallest set in F that is not a subset of any other set in F , and for any positive integer r, let F (r) denote the family of r-element sets in F . We say that a family A is of Hilton-Milner (HM ) type if for some A ∈ A, all sets in A\{A} have a common element x / ∈ A and intersect A. We show that if a hereditary family H is compressed and μ...
متن کاملCounting Families of Mutually Intersecting Sets
We determine the number of maximal intersecting families on a 9-set and find 423295099074735261880. We determine the number of independent sets of the Kneser graph K(9, 4) and find 366996244568643864340. Finally, we determine the number of intersecting families on an 8-set and find 14704022144627161780744368338695925293142507520.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Electr. J. Comb.
دوره 23 شماره
صفحات -
تاریخ انتشار 2016