No Arabic abstract
Consider the equation $mathcal{E}: x_1+ cdots+x_{k-1} =x_{k}$ and let $k$ and $r$ be positive integers such that $rmid k$. The number $S_{mathfrak{z},2}(k;r)$ is defined to be the least positive integer $t$ such that for any 2-coloring $chi: [1, t] to {0, 1}$ there exists a solution $(hat{x}_1, hat{x}_2, ldots, hat{x}_k)$ to the equation $mathcal{E}$ satisfying $displaystyle sum_{i=1}^kchi(hat{x}_i) equiv 0pmod{r}$. In a recent paper, the first author posed the question of determining the exact value of $S_{mathfrak{z}, 2}(k;4)$. In this article, we solve this problem and show, more generally, that $S_{mathfrak{z}, 2}(k, r)=kr - 2r+1$ for all positive integers $k$ and $r$ with $k>r$ and $r mid k$.
The purpose of the article is to provide an unified way to formulate zero-sum invariants. Let $G$ be a finite additive abelian group. Let $B(G)$ denote the set consisting of all nonempty zero-sum sequences over G. For $Omega subset B(G$), let $d_{Omega}(G)$ be the smallest integer $t$ such that every sequence $S$ over $G$ of length $|S|geq t$ has a subsequence in $Omega$.We provide some first results and open problems on $d_{Omega}(G)$.
Given a $t$-$(v, k, lambda)$ design, $mathcal{D}=(X,mathcal{B})$, a zero-sum $n$-flow of $mathcal{D}$ is a map $f : mathcal{B}longrightarrow {pm1,ldots, pm(n-1)}$ such that for any point $xin X$, the sum of $f$ over all blocks incident with $x$ is zero. For a positive integer $k$, we find a zero-sum $k$-flow for an STS$(u w)$ and for an STS$(2v+7)$ for $vequiv 1~(mathrm{mod}~4)$, if there are STS$(u)$, STS$(w)$ and STS$(v)$ such that the STS$(u)$ and STS$(v)$ both have a zero-sum $k$-flow. In 2015, it was conjectured that for $v>7$ every STS$(v)$ admits a zero-sum $3$-flow. Here, it is shown that many cyclic STS$(v)$ have a zero-sum $3$-flow. Also, we investigate the existence of zero-sum flows for some Steiner quadruple systems.
In this work we propose a combinatorial model that generalizes the standard definition of permutation. Our model generalizes the degenerate Eulerian polynomials and numbers of Carlitz from 1979 and provides missing combinatorial proofs for some relations on the degenerate Eulerian numbers.
In this paper, we prove that a graph $G$ with no $K_{s,s}$-subgraph and twin-width $d$ has $r$-admissibility and $r$-coloring numbers bounded from above by an exponential function of $r$ and that we can construct graphs achieving such a dependency in $r$.
We study zero-sum stochastic differential games where the state dynamics of the two players is governed by a generalized McKean-Vlasov (or mean-field) stochastic differential equation in which the distribution of both state and controls of each player appears in the drift and diffusion coefficients, as well as in the running and terminal payoff functions. We prove the dynamic programming principle (DPP) in this general setting, which also includes the control case with only one player, where it is the first time that DPP is proved for open-loop controls. We also show that the upper and lower value functions are viscosity solutions to a corresponding upper and lower Master Bellman-Isaacs equation. Our results extend the seminal work of Fleming and Souganidis [15] to the McKean-Vlasov setting.