Turán theorems for unavoidable patterns

نویسندگان

چکیده

Abstract We prove Turán-type theorems for two related Ramsey problems raised by Bollobás and Fox Sudakov. First, t ≥ 3, we show that any two-colouring of the complete graph on n vertices is δ -far from being monochromatic contains an unavoidable t-colouring when ≫ −1/ , where -colouring a clique order 2 in which one colour forms either or disjoint cliques . Next, tournament transitive t-tournament −1/[ /2] -tournament blow-up cyclic triangle obtained replacing each vertex Conditional well-known conjecture about bipartite Turán numbers, both our results are sharp up to implied constants hence determine magnitude corresponding off-diagonal numbers.

برای دانلود باید عضویت طلایی داشته باشید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

On Ramsey - Turán type theorems for hypergraphs

Let H’ be an r-uniform hypergraph. Let g=g(n; F) be the minimal integer so that any r-uniform hypergraph on n vertices and more than g edges contains a subgraph isomorphic to H’. Let e=f(n; H’, en) denote the minimal integer such that every r-uniform hypergraph on n vertices with more than e edges and with no independent set of .sn vertices contains a subgraph isomorphic to H’. We show that if ...

متن کامل

Unavoidable patterns

Let Fk denote the family of 2-edge-colored complete graphs on 2k vertices in which one color forms either a clique of order k or two disjoint cliques of order k. Bollobás conjectured that for every 2 > 0 and positive integer k there is an n(k, 2) such that every 2-edge-coloring of the complete graph of order n ≥ n(k, 2) which has at least 2n2 ) edges in each color contains a member of Fk. This ...

متن کامل

Turán theorems and convexity invariants for directed graphs

This paper is motivated by the desire to evaluate certain classical convexity invariants (specifically, the Helly and Radon numbers) in the context of transitive closure of arcs in the complete digraph. To do so, it is necessary to establish several new Turán type results for digraphs and characterize the associated extremal digraphs. In the case of the Radon number, we establish the following ...

متن کامل

More Turán-Type Theorems for Triangles in Convex Point Sets

We study the following family of problems: Given a set of n points in convex position, what is the maximum number triangles one can create having these points as vertices while avoiding certain sets of forbidden configurations. As forbidden configurations we consider all 8 ways in which a pair of triangles in such a point set can interact. This leads to 256 extremal Turán-type questions. We giv...

متن کامل

Strong Descent Numbers and Turán Type Theorems ( Extended Abstract )

For a permutation π in the symmetric group Sn let the total degree be its valency in the Hasse diagram of the strong Bruhat order on Sn, and let the down degree be the number of permutations which are covered by π in the strong Bruhat order. The maxima of the total degree and the down degree and their values at a random permutation are computed. Proofs involve variants of a classical theorem of...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

ژورنال

عنوان ژورنال: Mathematical proceedings of the Cambridge Philosophical Society

سال: 2021

ISSN: ['0305-0041', '1469-8064']

DOI: https://doi.org/10.1017/s030500412100027x