The 2-homeotoxal tilings of the plane and the 2-sphere

A complete enumeration is obtained of the finite tilings of the 2-sphere and of the infinite tilings of the plane which are normal and admit two transitivity classes of edges under topological automorphisms of the tiling. Every type is found to be representable by a tiling in which the edges form two transitivity classes under isometric symmetries of the tiling.     

Minimal 2-complexes and the D(2)-problem

We show that when there is a minimal algebraic -complex over the quaternion group which is not homotopy equivalent to the Cayley complex of the standard minimal presentation. This raises the possibility that Wall's D(2)-property might fail for .

     

A combinatorial approach to the 2D-Hermite and 2D-Laguerre polynomials

The first author has recently proved a Kibble–Slepian type formula for the 2D-Hermite polynomials $\{H_{m,n}(z,\overline{z})\}$ which extends the Poisson kernel for these polynomials. We provide a combinatorial proof of a closely related formula. The combinatorial structures involved are the so-called m-involutionary ℓ-graphs. They are enumerated in two different manners: first globally, then as the exponential of their connected components. We also give a combinatorial model for the 2D-Laguerre polynomials and study their linearization coefficients.     

Randomness of the square root of 2 and the giant leap,part 2

We prove that the “quadratic irrational rotation” exhibits a central limit theorem. More precisely, let α be an arbitrary real root of a quadratic equation with integer coefficients; say, \(\alpha = \sqrt 2\). Given any rational number 0 < x < 1 (say, x = 1/2) and any positive integer n, we count the number of elements of the sequence α, 2α, 3α, ..., nα modulo 1 that fall into the subinterval [0, x]. We prove that this counting number satisfies a central limit theorem in the following sense. First, we subtract the “expected number” nx from the counting number, and study the typical fluctuation of this difference as n runs in a long interval 1 ≤ n ≤ N. Depending on α and x, we may need an extra additive correction of constant times logarithm of N; furthermore, what we always need is a multiplicative correction: division by (another) constant times square root of logarithm of N. If N is large, the distribution of this renormalized counting number, as n runs in 1 ≤ n ≤ N, is very close to the standard normal distribution (bell shaped curve), and the corresponding error term tends to zero as N tends to infinity. This is the main result of the paper (see Theorem 1.1).     

关于Pell方程组X~2-3y~2=1与y~2-Dz~2=1的解

设D=2p_1…P_s(1≤s≤4),P_1…,P_s是互异的奇素数.证明了:Pell方程组x~2-3y~2=1,y~2-Dz~2=1除开D=2×7,2×3×5×7×13外,仅有平凡解(x,y,z)=(±2,±1,0).     

关于不定方程x~2-5ly~2=1与y~2-Dz~2=49的公解

设p_s(1≤s≤4)是互异的奇素数,D=2~tp_1~(a_1)p_2~(a_2)p_3~(a_4)p_4~(a_4)(a_i=0或1,1≤i≤4,t∈Z~+)时,不定方程x~2-51y~2=1与y~2-Dz~2=49仅当D=2~t×4999(t=1,3,5)时有非平凡公解(x,y,z)=(±50,±7,0).     

关于不定方程x~2-23y~2=1与y~2-Dz~2=25的公解

设p_s(1≤s≤4)是互异的奇素数,D=2~tp_1~α_1p_2~a_2p_3~a_3p_4~a_4(a_i=0或1,1≤i≤4,t∈Z~+)时,不定方程x~2-23y~2=1与y~2-Dz~2=25仅当D=2~t×1151(t=1,3,5,7,9)时有正整数解.     

关于丢番图方程x~2+y~2=p与x~2+2y~2=p的整数解

利用p次单位根e~((2πi)/p)作为原始材料,通过不同层次的组合,当p≡1(mod 4)时,给出了方程x~2+y~2=p的整数解.在此基础上,当p≡1(mod 8)时,进一步给出了x~2+2y~2=p的整数解.     

Exponentiation and the identity X2Y = (XY)2

Let G = SL(2,pⁿ ) with p odd. Let KG be the group algebra of G over an algebraically closed field K of characteristic p. In general, a finite dimensional basic algebra can be described by a quiver with relations. For KG, the quiver has been known. Namely the simple KG modules and their extensions determine it. The aim of this paper is to get the relations and describe the basic algebra of KG by the quiver with them.     

Combinatorial principles between RRT 2 2 and RT 2 2

We study the strength of some combinatorial principles weaker than Ramsey theorem for pairs over RCA0. First, we prove that Rainbow Ramsey theorem for pairs does not imply Thin Set theorem for pairs. Furthermore, we get some other related results on reverse mathematics using the same method. For instance, Rainbow Ramsey theorem for pairs is strictly weaker than ErdSs- Moser theorem under RCA0.     

Relationships Between the 2-Metric Dimension and the 2-Adjacency Dimension in the Lexicographic Product of Graphs

Given a connected simple graph \(G=(V(G),E(G))\), a set \(S\subseteq V(G)\) is said to be a 2-metric generator for G if and only if for any pair of different vertices \(u,v\in V(G)\), there exist at least two vertices \(w_1,w_2\in S\) such that \(d_G(u,w_i)\ne d_G(v,w_i)\), for every \(i\in \{1,2\}\), where \(d_G(x,y)\) is the length of a shortest path between x and y. The minimum cardinality of a 2-metric generator is the 2-metric dimension of G, denoted by \(\dim _2(G)\). The metric \(d_{G,2}: V(G)\times V(G)\longmapsto {\mathbb {N}}\cup \{0\}\) is defined as \(d_{G,2}(x,y)=\min \{d_G(x,y),2\}\). Now, a set \(S\subseteq V(G)\) is a 2-adjacency generator for G, if for every two vertices \(x,y\in V(G)\) there exist at least two vertices \(w_1,w_2\in S\), such that \(d_{G,2}(x,w_i)\ne d_{G,2}(y,w_i)\) for every \(i\in \{1,2\}\). The minimum cardinality of a 2-adjacency generator is the 2-adjacency dimension of G, denoted by \({\mathrm {adim}}_2(G)\). In this article, we obtain closed formulae for the 2-metric dimension of the lexicographic product \(G\circ H\) of two graphs G and H. Specifically, we show that \(\dim _2(G\circ H)=n\cdot {\mathrm {adim}}_2(H)+f(G,H),\) where \(f(G,H)\ge 0\), and determine all the possible values of f(G, H).     

Carlitz and the general 3φ2

In a letter dated March 3, 1971, L. Carlitz defined a sequence of polynomials, Φ _n (a,b; x, y; z), generalizing the Al-Salam & Carlitz polynomials, but closely related thereto. He concluded the letter by stating: “It would be of interest to find properties of Φ _n (a, b; x, y; z) when all the parameters are free.” In this paper, we reproduce the Carlitz letter and show how a study of Carlitz’s polynomials leads to a clearer understanding of the general ₃Φ₂ (a, b, c; d; e; q, z). Dedicated to my friend, Richard Askey. 2000 Mathematics Subject Classification Primary—33D20. G. E. Andrews: Partially supported by National Science Foundation Grant DMS 0200047.     

FFTs for the 2-Sphere-Improvements and Variations

Earlier work by Driscoll and Healy has produced an efficient algorithm for computing the Fourier transform of band-limited functions on the 2-sphere. In this article we present a reformulation and variation of the original algorithm which results in a greatly improved inverse transform, and consequent improved convolution algorithm for such functions. All require at most O(N log² N) operations where N is the number of sample points. We also address implementation considerations and give heuristics for allowing reliable and computationally efficient floating point implementations of slightly modified algorithms. These claims are supported by extensive numerical experiments from our implementation in C on DEC, HP, SGI and Linux Pentium platforms. These results indicate that variations of the algorithm are both reliable and efficient for a large range of useful problem sizes. Performance appears to be architecture-dependent. The article concludes with a brief discussion of a few potential applications.     

G2-manifolds and the ADM formalism

In this paper we study a Hamiltonian function on the cotangent bundle of the space of Riemannian metrics on a 3-manifold M and prove the orbits of the constrained Hamiltonian dynamical system correspond to $G_2$-manifolds foliated by hypersurfaces diffeomorphic to $M\times \mathrm{SO}(3)$.     

Dense codense predicates and the NTP2

We show that if T is any geometric theory having the NTP₂ then the corresponding theories of lovely pairs of models of T and of H‐structures associated to T also have the NTP₂. We also prove that if T is strong then the same two expansions of T are also strong.     

Area-length duality and the characteristic 2-chain

Translated fromMatematicheskie Zametki, Vol. 58, No. 3, pp. 445–446, September, 1995.     

关于Pell方程x~2-30y~2=1与y~2-Dz~2=4的公解

设p_1,…,p_s(1≤s≤4)是互异的奇素数.利用同余、递归序列、Pell方程的解的性质等证明了:当D=2p1…p_s,1≤s≤4时除开D为2×241外,Pell方程x~2-30y~2=1与y~2-Dz~2=4仅有平凡解(x,y,z)=(±11,±2,0).