Ramsey theory refers to questions of the form "how many objects are needed to guarantee that a given property of the collection holds?"

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Coloring of $K_{17}$

For any 3-coloring of $K_{17}$ I have to show there exists either a red, blue or green triangle. To start, can I use proof by contradiction with color red, blue, green? So $(0,0,136)$ means all 136 ...
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Mixed Tsirelson Norm

The following is a definition of a Banach space that is a generalization of the original Tsirelson space. Nowadays such a space is called a Mixed Tsirelson space; it was introduced by Argyros and ...
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Combinatorial Question using ramsey's theory or pigeonhole principle??

We are currently going over pigeonhole principle, ramsey's theorem (graphs and such). Stuck on this particular question: Within a group of an odd number of people, show that at least one person knows ...
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Two coloring questions and ramsays number

What is the smallest $n$ such that every 2-coloring of edges of $K_n$ contains a red or blue 4-cycle (not $K_4$)? I am given that $R(4,4) \le 18$ and $R(3,5) \le 14$ Any help is greatly appreciated!
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Graham's Number : Why so big?

Can someone give me an idea of how R.Graham reached Graham's Number as an upper bound on the solution of the related problem ? Thanks !
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van der Waerden's original proof

I am looking for a book/site which has the english translation of the proof of van der Waerden's theorem as presented by van der Waerden himself. In other words is the translation of the paper: ...
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number of potential couples

A potential couple is a pair of a man and a woman that like each other (assume that 'like' is a symmetric relation). Given a group of $M$ men and $W$ women, I want to know how many different ...
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Arbitrary ratio sequences on a partition of $\mathbb{R}$ (Partition regularity of fixed ratio sequences)

Background: This question arose purely recreationally and doesn't really fit into any context that I know of. Let $A \sqcup B = \mathbb{R}$ be a partition of the ...
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Conjectured Value of Ramsey Number $R(3,10)$

It is known that the value of the Ramsey number $R(3,10)$ is either 40, 41, or 42. Have any experts in the field offered a conjecture as to which it might be?
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The Erdős-Szekeres problem on points in convex position

The Erdős-Szekeres problem on points in convex position and its proof using Ramsey theorem are well know. The problem goes like this: For every natural number $k$ there exists a number $n(k)$ such ...
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History of Hindman's Theorem

At this blogpost about Hindman's Theorem, I read the following lines: 'I love the odd history so allow me to digress... etc. ' This sentence made me curious to know what this history looks ...
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Van der Waerden type numbers (for geometric progressions)

Van der Waerden theorem is true also for geometric progressions. Is there anything interesting in van der Waerden type numbers $ W'(r,k) $ derived from this version? ($ W'(r,k) $ is such that if the ...
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Questions on $R(K_l + \overline{K_t}, T_s) \le l(s-1)+t$

Following C. C. Rousseau and J. Sheehan "A class of ramsey problems involving trees" Journal of London Math. Soc. $1978$, I have some dudes about their proof for $R(K_l + \overline{K_t}, T_s) \le ...
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Van der Waerden number

The Van der Waerden number $w(l,k)$ is the least $n$ such that for every $k$-coloring of $[n]$ has a monochromatic $l$-term arithmetic progression. Prove that $w(l,k)>(lk^{l-1})^{1/2}$ Give some ...
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Ramsey (graph) theory question with tree and girth

Sorry for the abundance of questions I'm asking. Test is soon... Prove that for every tree $T$ and every $g \in \mathbb{N}$, exist $G$ with girth $g$, so that in any 2-edge-coloring of $G$ there is a ...
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Monochromatic degenerate triangles in a two-coloring of the plane

In a similar vein to a question I asked a few days ago: Do all two-colorings of $\mathbb{R}^2$ contain three points of the same color which form the vertices of a degenerate triangle of side-lengths ...
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Probability that a subset of a degree-regular graph shares at least a certain number of mutual connections

Consider a set of $n$ vertices of common degree $p$. What is the probability that some subset of $x$ vertices from $n$ share $q$ mutual connections within that group of size $x$? i.e. If we have ...
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Local Lemma on lower bounding R(k,k)

We aim to prove that if $k \ge 3$ and $e2^{1-\binom{k}{2}}\binom{n}{k-2} \le 1$ then $R(k,k) >n$ Now I understand that we colour the edges of $K_n$ red and black with probability 1/2. For each ...
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Link between Ramsey Theory, random graphs and spin glasses

As all three theories study the emergence of order, it would be natural if there were some links between: Ramsey theory; random graphs; spin glasses. Is there a textbook or an article that ...
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What was done to calculate the Ramsey numbers using a quantum computer?

I recently came across this paper titled Experimental determination of Ramsey numbers with quantum annealing I was wondering what exactly the gist of the paper, as I read it, it seems rather ...
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Hereditary and Pre-compact implies Compact

Lemma II.3.20 in the book Ramsey Methods in Analysis by Argyros and Todorcevic states that a pre-compact hereditary family $\mathcal{F}$ of finite subsets of $\mathbb{N}$ is compact. It is supposed to ...
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Some small (and probably easy) implication from combinatorics paper

I'm reading https://people.math.osu.edu/bergelson.1/PolSz.pdf . Question is about part from (1.7) on page 16. Why $ \lambda(\chi_{1})=\lambda(\chi_{1}) $? There's no problem if in 4-th verse ...
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2-colorings of arithmetic progression

Consider the following classical result: $\forall r \in \mathbb N : \exists N\in \mathbb N$ such that every 2-colored arithmetic progression of length N contains a monochromatic arithmetic ...
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proving an inequality by induction

Not sure how to proceed. I'm trying to prove that the following inequality is true. I know that $t_2 = 6$ and $t_3=17$ from the problem statement. The base case is obvious. $t_{r+1} \leq (r+1) (t_r ...