A NOTE ON 2IVm-p DESIGNS WITH THE MAXIMUM NUMBER OF CLEAR TWO-FACTOR INTERACTIONS

In this article, the authors obtain some theoretical results for 2_IV^m-p designsto have the maximum number of clear two-factor interactions by considering the number of two-factor interactions that are not clear. Several 2_IV^m-p designs with the maximum number of clear two-factor interactions, judged using these results, are provided for illustration.     

Deformation of Complete Intersections in the Plane

We study deformations of zero-dimensional complete intersectionsin the plane, and prove the following results. (1) Two complexnon-singular curves intersecting at r points with multiplicitiesd₁,...,d_r can be deformed into curves intersecting (at somepoints) with multiplicities d'₁,...,d'_s which are arbitraryprescribed partitions of the numbers d₁,...,d_r. (2) Two realcurves intersecting with multiplicity at most 2 at each of theirreal common points can be deformed so that all real multipleintersection points split into real simple intersection points.1991 Mathematics Subject Classification 14M10, 14P05.     

Generalized Ramsey Theory for Graphs V. the Ramsey Number of a Digraph

Continuing this series of papers on generalized Ramsey theoryfor graphs, we define the Ramsey number r(D_l, D₂) of two digraphsD₁ and D₂ as the minimum p such that every 2-colouring of thearcs (directed lines) of DK_P (the complete symmetric digraphof order p) contains a monochromatic D₁ or D₂. It is shown(Theorem1) that this number exists if and only if D₁ or D₂ is acyclic.Then r(D), the diagonal Ramsey number of a given acyclic digraphD, is defined as r(D, D). Notation: D' is the converse of D,GD is the underlying graph of D, DG is the symmetric digraphof G, and T_p is the transitive tournament of order p. Let r(m,n) be the traditional Ramsey number of the two complete graphsK_m and K_n. Finally, let S_n be the star with n arcs from onepoint u to n points v_i. Assuming the Ramsey numbers under discussionexist, we prove the following results: THEOREM 2. r(D₁, D₂) = r(D₁' D₂'). THEOREM 3. r(D₁, D₂) r(GD₁, GD₂). THEOREM 4. r(D₁, D₂) r(T_P1, T_P2) if both D₁ and D₂ (with p₁and p₂ points respectively) are acyclic. THEOREM 5. r(T_m, T_n) = r(m, n). THEOREM 6. r(m, ri) r(T_m, DK_n) r(2^m–1, n). THEOREM 7. r(S_m, S_n) = r(S_m, S_n') = m+n. Finally, we establish all Ramsey numbers r(D₁, D₂) for digraphswithout isolates and with less than four points, and all diagonalRamsey numbers r(D) of acyclic digraphs without isolates withless than five points.     

Properties of Some Generalized Hypergeometric Functions Governing Coupling at Transition Points

Understanding of wave propagation problems is enhanced by consideringgeneralizations to differential equations of order 2n. In particular,reflection and coupling of waves at transition points can involvecertain types of generalized hypergeometric functions. In thispaper, properties of _oF_2n-1 functions are considered systematically,when the parameters are specially chosen for application totransition points; a wide range of interesting properties unfolds,which recall the properties of Bessel functions when n = 1.     

A WKB analysis of the buckling condition for a cylindrical shell of arbitrary thickness subjected to an external pressure

We consider the plane-strain buckling of a cylindrical shellof arbitrary thickness which is made of a Varga material andis subjected to an external hydrostatic pressure on its outersurface. The WKB method is used to solve the eigenvalue problemthat results from the linear bifurcation analysis. We show thatthe circular cross-section buckles into a non-circular shapeat a value of µ₁ which depends on A₁/A₂ and a mode number,where A₁ and A₂ are the undeformed inner and outer radii, andµ₁ is the ratio of the deformed inner radius to A₁. Inthe large mode number limit, we find that the dependence ofµ₁ on A₁/A₂ has a boundary layer structure: it is constantover almost the entire region of 0 < A₁/A₂ < 1 and decreasessharply from this constant value to unity as A₁/A₂ tends tounity. Our asymptotic results for A₁ – 1 = O(1) and A₁– 1 = O(1/n) are shown to agree with the numerical resultsobtained by using the compound matrix method.     

On the denominators of rational points on elliptic curves

Let x(P) = A_P/B²_P denote the x-coordinate of the rational pointP on an elliptic curve in Weierstrass form. We consider whenB_P can be a perfect power or a prime. Using Faltings' theorem,we show that for a fixed f > 1, there are only finitely manyrational points P with B_P equal to an fth power. Where descentvia an isogeny is possible, we show that there are only finitelymany rational points P with B_P equal to a prime, that thesepoints are bounded in number in an explicit fashion, and thatthey are effectively computable. Finally, we prove a strongerversion of this result for curves in homogeneous form.     

一类算子值解析函数族的极值点

设 H 是一个Hilbert空间. B(H) 表示所有H 到 H 的有界线性算子构成的Banach空间. 设 T= {f(z): f(z)=zI-∑^∞_n=2 zⁿA_n 在单位圆盘|z|<1上解析, 其中系数A_n是 H 到 H 的紧正Hermitian算子, I 表示 H 上的恒等算子, ∑^∞_n=2 n(A_n x, x) ≤1 对所有x ∈H, ∣|x∣∣=1 成立. 该文研究了函数族 T 的极值点.     

Energy Sharing in the Random Vibration of Non-linearly Coupled Modes

If small non-linear terms couple the (linear) modes of a multidegree-of-freedomsystem, energy can flow from one mode to another and vice versa.In this paper a perturbation method is used to calculate theaverage rate of energy transfer between nonlinearly coupledmodes. Each mode is assumed to be subjected to an independentsource of stationary, Gaussian, random excitation, and the couplingterms, which are conservative, are of the form x_rx_s, and x_r, where x_r and x_s are the normal co-ordinates of the linearizedsystem. The principal result is that, if the excitation is whitenoise, no flow of energy occurs when each mode has the sameenergy. Thus, as predicted by the results of statistical mechanics,the equilibrium state for white noise excitation is that ofequipartition of energy between the modes. When the modal energiesare not equal, energy flows from modes of higher energy to modesof lower energy, and the rate of energy transfer is greatestfor those modes whose natural frequencies satisfy internal resonancecombinations. An application of the results of the paper is in calculatingnoise transmission between connected structures, where vibrationalmodes may be coupled by small nonlinear terms. If the naturalfrequencies of the coupled modes are suitably related, it isshown that very small coupling may cause considerable excitationof otherwise dormant parts of a structure. The paper may alsobe of interest in the study of molecular reactions and biologicalrhythms, and of non-linear wave interactions in such areas asplasma dynamics, turbulence, and the theory of water waves.     

Weierstrass Points on X0(pM) and Supersingular j-Invariants

Weierstrass points are special points on a Riemann surface thatcarry a lot of information. Ogg studied such points on X₀(pM)(for M such that X₀(M) has genus zero and p prime with p M),and he proved that if Q is a Q-rational Weierstrass point onX₀(pM), then its reduction modulo p is supersingular. The papershows that, for square-free M on the list, all supersingularj-invariants are obtained in this way. Furthermore, for mostcases where M is prime, the explicit correspondence betweenWeierstrass points and supersingular j-invariants in characteristicp is described. Along the way, a useful formula of Rohrlichfor computing a certain Wronskian of modular forms modulo pis generalized.     

On Sets that Meet Every Hyperplane in n-Space in at Most n Points

A simple proof that no subset of the plane that meets everyline in precisely two points is an F-set in the plane is presented.It was claimed that this result can be generalized for setsthat meet every line in either one point or two points. No proofof this assertion is known, however. The main results in thispaper form a partial answer to the question of whether the claimis valid. In fact, it is shown that a set that meets every linein the plane in at least one but at most two points must bezero-dimensional, and that if it is -compact then it must bea nowhere dense G-set in the plane. Generalizations for similarsets in higher-dimensional Euclidean spaces are also presented.     

代数体函数的正规族定理

设F是定义在球面V的子集D上的一族代数体函数,若F中所有f的分支点之和为有限个，且存在三个固定的复值a₁,a₂,a₃使得对每个f都有∑³_k=1n(D,a_k, f)≤1,则F在D内正规.     

Extended Generalized Hexagons and the Suzuki Chain

Four extended generalized hexagons related to the simple groupsG₂(2)', PSU₄(3), HJ and Suz are characterized by the conditionthat any triple of points {x, y, z} is a clique of the pointgraph not in a circle of the extended hexagon if and only ifthe distance of y and z in the residue at x is 3.     

Conformal Versus Topological Conjugacy of Automorphisms on Compact Riemann Surfaces

We produce a family of algebraic curves (closed Riemann surfaces)S admitting two cyclic groups H₁ and H₂ of conformal automorphisms,which are topologically (but not conformally) conjugate andsuch that S/H_i is the Riemann sphere . The relevance of thisexample is that it shows that the subvarieties of moduli spaceconsisting of points parametrizing curves which occur as cycliccoverings (of a fixed topological type) of need not be normal.1991 Mathematics Subject Classification 14H10, 30F10.     

具有缺项系数的几类解析函数族的性质

S*表示所有在单位圆盘 D 内解析且满足条件 f(0)=f′ (0)-1=0的星形函数族, K 表示所有在 D内解析且满足条件 f(0)=f′ (0)-1=0 的凸函数族, P 表示所有在 D 内解析且满足条件p(0)=1, Rep(z)>0 的函数族. 设P_n={p(z): p(z)=1+a_nzⁿ+a_n+1zⁿ⁺¹+…∈ P}, S*_n={f (z): f(z)=z+a_nzⁿ+a_n+1zⁿ⁺¹+…∈ S*}, K_n={f (z): f (z)=z+a_nzⁿ+a_n+1zⁿ⁺¹+…∈ K}. L_Sn*={g(z)=ln f(z)/z, f ∈ S_n*}, 其中对数函数取使得ln1=0的那个单值解析分支. 该文研究了函数族S_n^*, K_n和L_Sn*的性质, 找出了解析函数族L_Sn*的极值点与支撑点,并对S*_n与K_n的极值点和支撑点作了一些探讨.     

Arbitrary-norm hyperplane separation by variable neighbourhood search

^** Email: alejandro.karam{at}hec.ca^*** Email: gilles.caporossi{at}gerad.ca^**** Email: pierre.hansen{at}gerad.ca We consider the problem of separating two sets of points ina Euclidean space with a hyperplane that minimizes the sum ofp-norm distances to the plane of points lying on the ‘wrong’side of the plane. A variable neighbourhood search heuristicis used to determine the plane coefficients. For a set of exampleswith L₁-norm, L₂-norm and L-norm, for which the exact solutioncan be computed, we show that our algorithm finds it in mostcases and gets good approximations in the others. The use ofour heuristic solutions for problems in these norms can dramaticallyaccelerate exact algorithms. Our method can be applied on verylarge instances that are intractable by exact algorithms. Sincethe proposed approach works for truly arbitrary norms (otherthan the traditional 1, 2 and ), we can explore for the firsttime the effects of the choice of p on the generalization propertiesof p-norm hyperplane separation.     

Constructive analysis of Takens-Bogdanov points with Z2-symmetry

Assuming a 2-parameter-dependent family of smooth Z₂-equivariantvector fields, a symmetry-breaking Takens-Bogdanov point isconsidered as an isolated organizing centre. Two branches ofsymmetry-breaking and asymmetric Hopf bifurcation points aswell as one branch of Z₂-pitchforks which emanate from the organizingcentre are analyzed via asymptotic expansions. Leading termsof these expansions are calculated explicitly. The input dataare differentials (up to third order) of the mapping evaluatedat the organizing centre along specified directions.     

Some Properties and Applications of Simple Orthogonal Matrices

Conditions are found for a general transformation in the planeof two vectors u and v to be orthogonal. The results characterizea rotation in the (u, v)-plane by the angle ø betweenu and v and the angle of rotation. When ø = /2 the Jacobirotation matrix is a special case, but other choices of øare interesting. The rotation that maps a single vector x intoa vector y of the same size, by rotating in the (x, y)-plane,is found and this may be used in much the same way that Householdertransforms are used. If (x₁, y₁) and (x₂, y₂) are pairs of vectorscompatible in size and angle, the orthogonal matrix that rotatesin a suitably chosen plane so that x₁ x₂ and y₁ y₂ is found.This has applications in mapping two columns of a matrix toa simple form, similar to Householder operations on a singlecolumn.     

关于单位圆内解析系数的线性微分方程的复振荡理论

该文研究了线性微分方程L(f)=f^(k)+A_k-1(z)f^(k-1)+ ^… +A₀(z)f=F(z) (k∈ N)的复振荡理论, 其中系数A_j(z) (j=0, ^… , k-1)和F(z)是单位圆△={z:|z|<1}内的解析函数. 作者得到了几个关于微分方程解的超级, 零点的超收敛指数以及不动点的精确估计的定理.     

Recovering asymptotics of metrics from fixed energy scattering data

The problem of recovering the asymptotics of a short range perturbation of the Euclidean metric on Rⁿ from fixed energy scattering data is studied. It is shown that if two such metrics, g₁,g₂, have scattering data at some fixed energy which are equal up to smoothing, then there exists a diffeomorphism N 'fixing infinity' such that N^*g₁-g₂ is rapidly decreasing. Given the scattering matrix at two energies, it is shown that the asymptotics of a metric and a short range potential can be determined simultaneously. These results also hold for a wide class of scattering manifolds.