How Tight Is the Bollobás-Komlós Conjecture?

The bipartite case of the Bollobás and Komlós conjecture states that for every j₀, %>0 there is an !=!(j₀, %) >0 such that the following statement holds: If G is any graph with minimum degree at least n$\displaystyle {n \over 2}+%n then G contains as subgraphs all n vertex bipartite graphs, H, satisfying¶H)hj₀ \quad {\rm and} \quad b(H)h!n.$j (H)hj₀ \quad {\rm and} \quad b(H)h!n.¶Here b(H), the bandwidth of H, is the smallest b such that the vertices of H can be ordered as v₁, …, v_n such that v_i~_Hv_j implies |imj|hb.¶ This conjecture has been proved in [1]. Answering a question of E. Szemerédi [6] we show that this conjecture is tight in the sense that as %̂ then !̂. More precisely, we show that for any 0 such that that !(j₀, %)Д %.     

How Fast can a Subharmonic Function Decay Along a Ray?

Much is known about the connection between the growth and decayof subharmonic functions. The results indicate that there isa general principle: asubharmonic function cannot decay ‘toofast’ relative to its growth.Three theorems are provedwhich, together with work previously published elsewhere, givea fairly complete account of how this principle works out fora subharmonic function having extremal decay along a ray. 1991Mathematics Subject Classification: 30D20, 31A05.     

How Fast Does It Diverge? Discrete Hedging Error with Transaction Costs

Acta Mathematicae Applicatae Sinica, English Series - In the present paper, we focus on the diverging behavior of discrecte hedging error with transaction costs. We added the hedging cost to the...     

Is the dying individual the oldest?

Consider a population in which the birth times are a Poisson process with rate γ lifetimes are independent and identically distributed and lifetimes are independent of the birth process. In the paper we provide methods for calculation of several quantities involving the oldest member (senior) of the population. In particular we study the senior's age process and the point process of seniors' deaths obtained by dependent thinning of a Poisson process.     

How Fast and in what Sense(s) Does the Calderón Reproducing Formula Converge?

We prove that a very general form of the Calderón reproducing formula converges in L ^p (w), for all 1<p<∞, whenever w belongs to the Muckenhoupt class A _p . We show that the formula converges whether we interpret its defining integral, in very natural senses, as a limit of L ^p (w)-valued Riemann or Lebesgue integrals. We give quantitative estimates on their rates of convergence (or, equivalently, on the speed at which the errors go to 0) in L ^p (w).     

How Common Is the Common Core? A Global Analysis of Math Teaching and Learning

The U.S. educational system is undergoing rapid and substantial changes with many states grappling with the adoption of the Common Core State Standards in Mathematics (CCSSM). Important research questions remain unanswered regarding the potential efficacy of the CCSSM to improve student math performance compared with students around the globe. This article utilized TIMSS 2007 8th‐grade math assessment results and curricular frameworks to (1) measure the degree of overlap between the CCSSM and TIMSS standards, and (2) use this finding to create a predictive model to determine the potential efficacy of the CCSSM in improving the U.S. 8th‐grade student math performance compared with six culturally matched, TIMSS‐assessed countries, provinces, and states. Comparisons of CCSSM and TIMSS‐assessed jurisdictions show that the CCSSM holds many items in common with TIMSS‐assessed jurisdictions, but lacks rigor in some key areas. The CCSSM deficiencies include algebraic knowledge and problem solving at the 8th‐grade level, and are a significant detractor from the CCSSM when compared with TIMSS.     

How does the core sit inside the mantle?

The k‐core, defined as the maximal subgraph of minimum degree at least k, of the random graph has been studied extensively. In a landmark paper Pittel, Wormald and Spencer [J Combin Theory Ser B 67 (1996), 111–151] determined the threshold d_k for the appearance of an extensive k‐core. The aim of the present paper is to describe how the k‐core is “embedded” into the random graph in the following sense. Let and fix . Colour each vertex that belongs to the k‐core of in black and all remaining vertices in white. Here we derive a multi‐type branching process that describes the local structure of this coloured random object as n tends to infinity. This generalises prior results on, e.g., the internal structure of the k‐core. In the physics literature it was suggested to characterize the core by means of a message passing algorithm called Warning Propagation. Ibrahimi, Kanoria, Kraning and Montanari [Ann Appl Probab 25 (2015), 2743–2808] used this characterization to describe the 2‐core of random hypergraphs. To derive our main result we use a similar approach. A key observation is that a bounded number of iterations of this algorithm is enough to give a good approximation of the k‐core. Based on this the study of the k‐core reduces to the analysis of Warning Propagation on a suitable Galton‐Watson tree. © 2017 Wiley Periodicals, Inc. Random Struct. Alg., 51, 459–482, 2017     

How old are the Platonic Solids?

Recently a belief has spread that the set of five Platonic Solids has been known since prehistoric times, in the form of carved stone balls from Scotland, dating from the Neolithic period. A photograph of a group of these objects has even been claimed to show mathematical understanding of the regular solids, a millennium or so before Plato. I argue that this is not so. The archaeological and statistical evidence do not support this idea, and it has been shown that there are problems with the photograph. The high symmetry of many of these objects can readily be explained without supposing any particular mathematical understanding on the part of the creators, and there seems to be no reason to doubt that the discovery of the set of five regular solids is contemporary with Plato.     

How quadratic are the natural numbers?

Abstract. For natural numbers n we inspect all factorizations n = ab of n with a ￡ ba \le b in \Bbb N\Bbb N and denote by n=a_n b_nn=a_n b_n the most quadratic one, i.e. such that b_n - a_nb_n - a_n is minimal. Then the quotient k(n) : = a_n/b_n\kappa (n) := a_n/b_n is a measure for the quadraticity of n. The best general estimate for k(n)\kappa (n) is of course very poor: 1/n ￡ k(n) ￡ 11/n \le \kappa (n)\le 1. But a Theorem of Hall and Tenenbaum [1, p. 29], implies(logn)^-d-e ￡ k(n) ￡ (logn)^-d(\log n)^{-\delta -\varepsilon } \le \kappa (n) \le (\log n)^{-\delta } on average, with d = 1 - (1+log₂  2)/log2=0,08607 ?\delta = 1 - (1+\log _2 \,2)/\log 2=0,08607 \ldots and for every e > 0\varepsilon >0. Hence the natural numbers are fairly quadratic.¶k(n)\kappa (n) characterizes a specific optimal factorization of n. A quadraticity measure, which is more global with respect to the prime factorization of n, is k^*(n): = ?_{1 ￡ a ￡ b, ab=n} a/b\kappa ^*(n):= \textstyle\sum\limits \limits _{1\le a \le b, ab=n} a/b. We show k^*(n) ~ \frac 12\kappa ^*(n) \sim \frac {1}{2} on average, and k^*(n)=W(2^{\frac 12(1-e) log n/log ₂n})\kappa ^*(n)=\Omega (2^{\frac {1}{2}(1-\varepsilon ) {\log}\, n/{\log} _2n})for every e > 0\varepsilon>0.     

How to use the Limit Laws?

We used tables and graphs by using graphing-calculator to guess values of limits,however,we found methods we used don’t always lead to the correct answer.Theproperties of limits have been found.It iseasy to believe they are true.For example,iff(x)is close to Land g(x)is close to M,itis reasonable to get the result that f(x)+g     

How to prove the integral test?

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Bandit过程及其应用

本文有两个目的.第一,对Bandit过程这一学科的主要概念及结果作一次系统性的介绍.第二,综述Bandit过程的模型,计算与应用的最新发展.本文刻画了Bandit过程与马氏决策规划的关系.通过考虑理论上或方法论上的局限,实际中或计算上的困难,以及应用中的限制.我们讨论一些重要的争端和公开的问题.     

How to use the method of the improvising differentiation?

<正>We know the Substitution Rule,which is based on the following identity in differentiation.∫f(g(x))g′(x)dx=∫f(u)du(where u=g(x)).Now,we'll talk about how to use the method of the improvising differentiation,and give some examples by using basic     

Is the critical percolation probability local?

We show that the critical probability for percolation on a d-regular non-amenable graph of large girth is close to the critical probability for percolation on an infinite d-regular tree. We also prove a finite analogue of this statement, valid for expander graphs, without any girth assumption.     

Is the linearized Boltzmann-Enskog operator dissipative?

In this paper, it is shown that the linearized Boltzmann-Enskog collision operator cannot be dissipative in the L₂-space setting contrarily to the linearized Boltzmann operator. Some estimates useful for the spectral theory are given.