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We prove that the Ramsey number $R(5,5)$ is less than or equal to~$46$. The proof uses a combination of linear programming and checking a large number of cases by computer. All of the computations were independently implemented by both…

Combinatorics · Mathematics 2025-09-03 Vigleik Angeltveit , Brendan D. McKay

We establish new lower bounds for $28$ classical two and three color Ramsey numbers, and describe the heuristic search procedures we used. Several of the new three color bounds are derived from the two color constructions; specifically, we…

Combinatorics · Mathematics 2015-07-21 Geoffrey Exoo , Milos Tatarevic

The Ramsey number r(K_3,Q_n) is the smallest integer N such that every red-blue colouring of the edges of the complete graph K_N contains either a red n-dimensional hypercube, or a blue triangle. Almost thirty years ago, Burr and Erd\H{o}s…

Combinatorics · Mathematics 2013-02-18 Gonzalo Fiz Pontiveros , Simon Griffiths , Robert Morris , David Saxton , Jozef Skokan

This paper introduces Farey Recursive Functions and investigates their basic properties. Farey Recursive Functions are a special type of recursive function from the rationals to a commutative ring. The recursion of these functions is…

Geometric Topology · Mathematics 2021-07-28 Eric Chesebro , Cory Emlen , Kenton Ke , Denise LaFontaine , Kelly McKinnie , Catherine Rigby

A statistical inference for random coefficient first-order autoregressive model $[RCAR(1)]$ was investigated by P.M. ROBINSON (1978) in which the coefficients varying over individuals. In this paper we attempt to generalize this result to…

Statistics Theory · Mathematics 2008-11-13 A. Bouchemella , A. Bibi

We construct an edge-colored digraph analogous to Mathon's construction for undirected graphs. We show that this graph is connected to the $k$-th power Paley digraphs and we use this connection to produce improved lower bounds for…

Combinatorics · Mathematics 2024-08-13 Dermot McCarthy , Chris Monico

We present a unified approach to proving Ramsey-type theorems for graphs with a forbidden induced subgraph which can be used to extend and improve the earlier results of Rodl, Erdos-Hajnal, Promel-Rodl, Nikiforov, Chung-Graham, and…

Combinatorics · Mathematics 2007-12-27 Jacob Fox , Benny Sudakov

From the literature it is known that orthogonal polynomials as the Jacobi polynomials can be expressed by hypergeometric series. In this paper, the authors derive several contiguous relations for terminating multivariate hypergeometric…

Numerical Analysis · Mathematics 2023-10-05 Sven Beuchler , Tim Haubold , Veronika Pillwein

Gaitan and Clark [Phys. Rev. Lett. 108, 010501 (2012)] have recently presented a quantum algorithm for the computation of the Ramsey numbers R(m, n) using adiabatic quantum evolution. We consider that the two-color Ramsey numbers R(m, n; r)…

Quantum Physics · Physics 2013-02-21 Ri Qu , Yan-ru Bao

Chv\'atal, R\"odl, Szemer\'edi and Trotter proved that the Ramsey numbers of graphs of bounded maximum degree are linear in their order. We prove that the same holds for 3-uniform hypergraphs. The main new tool which we prove and use is an…

Combinatorics · Mathematics 2007-05-23 Oliver Cooley , Nikolaos Fountoulakis , Daniela Kühn , Deryk Osthus

One of the most popular and studied recursive series is the Fibonacci sequence. It is challenging to see how Fibonacci numbers can be used to generate other recursive sequences. In our article, we describe some families of integer…

Number Theory · Mathematics 2024-03-25 Kálmán Liptai , László Németh , Tamás Szakács , László Szalay

Heckman and Opdam introduced a non-symmetric analogue of Jack polynomials using Cherednik operators. In this paper, we derive a simple recursion formula for these polynomials and formulas relating the symmetric Jack polynomials with the…

q-alg · Mathematics 2008-02-03 Friedrich Knop , Siddhartha Sahi

We introduce the notion of reflexivity for combinatory algebras. Reflexivity can be thought of as an equational counterpart of the Meyer-Scott axiom of combinatory models, which indeed allows us to characterise an equationally definable…

Logic in Computer Science · Computer Science 2022-07-01 Marlou M. Gijzen , Hajime Ishihara , Tatsuji Kawai

It is well known that many theorems in recursion theory can be "relativized". This means that they remain true if partial recursive functions are replaced by functions that are partial recursive relative to some fixed oracle set. Uspensky…

Logic · Mathematics 2018-11-16 Alexander Shen

We initiate the study of Ramsey numbers of trails. Let $k \geq 2$ be a positive integer. The Ramsey number of trails with $k$ vertices is defined as the the smallest number $n$ such that for every graph $H$ with $n$ vertices, $H$ or the…

Discrete Mathematics · Computer Science 2022-09-14 Masatoshi Osumi

Let $Q(n)$ denote the number of integers $1 \leq q \leq n$ whose prime factorization $q= \prod^{t}_{i=1}p^{a_i}_i$ satisfies $a_1\geq a_2\geq \ldots \geq a_t$. Hardy and Ramanujan proved that $$ \log Q(n) \sim \frac{2\pi}{\sqrt{3}}…

Number Theory · Mathematics 2022-07-20 Asaf Cohen Antonir , Asaf Shapira

Let $K\_{[k,t]}$ be the complete graph on $k$ vertices from which a set of edges, induced by a clique of order $t$, has been dropped. In this note we give two explicit upper bounds for $R(K\_{[k\_1,t\_1]},\dots, K\_{[k\_r,t\_r]})$ (the…

Combinatorics · Mathematics 2014-12-15 Jonathan Chappelon , Luis Pedro Montejano , Jorge Luis Ramírez Alfonsín

We characterize the strength, in terms of Weihrauch degrees, of certain problems related to Ramsey-like theorems concerning colourings of the rationals and of the natural numbers. The theorems we are chiefly interested in assert the…

Logic in Computer Science · Computer Science 2023-12-05 Arno Pauly , Cécilia Pradic , Giovanni Solda

In this paper, the asymptotic formulas for Eulerian numbers, refined Eulerian numbers and the coefficients of descent polynomials are obtained directly from the spline interpretations of these numbers. Having related these numbers directly…

Combinatorics · Mathematics 2010-02-02 Renhong Wang , Yan Xu

The key tool of this paper is a new Carleman estimate for an arbitrary parabolic operator of the second order for the case of reversed time data. This estimate works on an arbitrary time interval. On the other hand, the previously known…

Analysis of PDEs · Mathematics 2020-01-08 Michael V. Klibanov , Anatoly G. Yagola