Irreducible polynomials over finite fields. I

A function H_n(a₁, a₂, a₃) is found, computing the number of normalized irreducible polynomials of degree n over a finite field F_q, with the first three coefficients a₁, a₂, and a₃ fixed for n = 4. The function is expressed via some sums of characters admitting “good” estimates. In particular, the following theorem is proved: If q = 3m + 1, a ∈ k^*, and N (a) = H₄(0, 0, a), then $$N(a) = \frac{1}{4}(q - 2\operatorname{Re} [(\lambda (a) - \eta ( - 1)\bar \lambda (a/2))J(\lambda ,\lambda )] - \eta ( - 1)),$$ where η is a quadratic character of the field k = F_q, λ is a nontrivial cubic character, and J(λ, λ) is the known Jacobi sum.     

Irreducibility and Reduction Number of Ideals in a One Dimensional Analytically Irreducible Ring

Let R be a one dimensional analytically irreducible ring, and let I be an integral ideal of R. We study the irreducibility and the reduction number of I in relation with the corresponding semigroup ideal v(I) in v(R), where v(R) is the semigroup of values of R. It turns out that, if v(I) is irreducible, then I is irreducible, but the converse does not hold in general. We show also that the reduction number of I in R can assume any positive value less than the multiplicity of R and can be different from the reduction number of v(I).     

Free Algebras over Biregularizations of Varieties

Let : F N be a type of algebras, where F is a set of fundamental operation symbols and N is the set of nonnegative integers. An identity of type is called biregular if the sets of variables in and are identical and the sets of fundamental operation symbols in and are identical. If K is a variety of type , we denote by K_b the variety of type defined by all biregular identities from Id(K). K_b will be called the biregularization of K. In this paper we give a representation of free algebras over K_b by means of free algebras over K.     

Structure of Irreducible Homomorphisms to/from Free Modules

The primary goal of this paper is to investigate the structure of irreducible monomorphisms to and irreducible epimorphisms from finitely generated free modules over a noetherian local ring. Then we show that over such a ring, self-vanishing of Ext and Tor for a finitely generated module admitting such an irreducible homomorphism forces the ring to be regular.     

二次高斯和与有限域上方程的解数

设f∈F_q[x_1,…,x_n]是一个n元多项式,其中F_q为q元有限域.用N(f)表示方程f=0在F_q~n中解的个数.寻找N(f)的表达式在有限域研究中具有重要意义.利用二次特征与二次高斯和,给出了有限域上一类方程的解数公式.     

Irreducible modules over a Jordan plane over a field of characteristic zero

Irreducible modules over a Jordan plane over a field of characteristic zero are considered. All finite-dimensional modules are described. Examples of infinite-dimensional irreducible modules are constructed.     

有限域上一类不可约多项式（英文）

设F_q为q元有限域,其中q是素数p的幂,设n是一个正整数.F_q上一个n次首一多项式f(x)的迹定义为x~(n-1)的系数.令N_q(n,t)表示F_q上迹为t∈F_q的n次首一不可约多项式的个数.基于给定多项式的普通分解与其线性化q-相伴式的符号分解之间的关系,本文给出了一种计算N_q(n,t)的新途径.     

Error Bounds of Constrained Quadratic Functions and Piecewise Affine Inequality Systems

We consider the error bounds for a piecewise affine inequality system and present a necessary and sufficient condition for this system to have an error bound, which generalizes the Hoffman result. Moreover, we study the error bounds of the system determined by a quadratic function and an abstract constraint.     

Affine normability of partial sums of I.I.D. random vectors: A characterization

Summary Let X, X ₁,X ₂,... be i.i.d. d-dimensional random vectors with partial sums S _n . We identify the collection of random vectors X for which there exist non-singular linear operators T _n and vectors _n ^d such that {(T _n (S _n – _n )),n>=1} is tight and has only full weak subsequential limits. The proof is constructive, providing a specific sequence {T _n }. The random vector X is said to be in the generalized domain of attraction (GDOA) of a necessarily operator-stable law if there exist {T _n } and { _n } such that (T _n (S _n – _n )). We characterize the GDOA of every operator-stable law, thereby extending previous results of Hahn and Klass; Hudson, Mason, and Veeh; and Jurek. The characterization assumes a particularly nice form in the case of a stable limit. When is symmetric stable, all marginals of X must be in the domain of attraction of a stable law. However, if is a nonsymmetric stable law then X may be in the GDOA of even if no marginal is in the domain of attraction of any law.This paper was presented in the special session on Asymptotic Behavior of Sums at the Annual IMS Meeting in Cincinnati, August 18, 1982This research was supported in part by National Science Foundation Grants MCS-81-01895 and MCS-83-01326This research was supported in part by National Science Foundation Grants MCS-80-64022 and MCS-83-01793     

Correction: Abelian Varieties defined over their Fields of Moduli, I

Bull London Math. Soc, 4 (1972), 370–372. The proof of the theorem contains an error. Before giving acorrect proof, we state two lemmas. LEMMA 1. Let K/k be a cyclic Galois extension of degree m, let generate Gal (K/k), and let (A, I, ) be defined over K. Supposethat there exists an isomorphism :(A,I,) (A, I, ) over K suchthat v^m–1 ... = 1, where v is the canonical isomorphism(A^m, I^m, ^m) (A, I, ). Then (A, I, ) has a model over k, whichbecomes isomorphic to (A, I, ) over K. Proof. This follows easily from [7], as is essentially explainedon p. 371. LEMMA 2. Let G be an abelian pro-finite group and let : G Q/Z be a continuous character of G whose image has order p.Then either: (a) there exist subgroups G' and H of G such that H is cyclicof order p^m for some m, (G') = 0, and G = G' x H, or (b) for any m > 0 there exists a continuous character m ofG such that p^m _m = . Proof. If (b) is false for a given m, then there exists an element G, of order p^r for some r m, such that () ¦ 0. (Considerthe sequence dual to 0 Ker (p^m) G ^pm G). There exists an opensubgroup G_o of G such that (G₀) = 0 and has order p^r in G/G₀.Choose H to be the subgroup of G generated by , and then aneasy application to G/G₀ of the theory of finite abelian groupsshows the existence of G' (note that () ¦ 0 implies that is not a p-th. power in G). We now prove the theorem. The proof is correct up to the statement(iv) (except that (i) should read: F' k₁ F'ab). To removea minor ambiguity in the proof of (iv), choose to be an elementof Gal (F'_ab/k₂) whose image $$\stackrel{\¯}{\sigma}$$ in Gal (k₁/k₂) generates this last group. The error occursin the statement that the canonical map v : A^P A acts on pointsby sending a^p a; it, of course, sends a a. The proof is correct, however, in the case that it is possibleto choose so that ^p = 1 (in Gal (F'/k₂)). By applying Lemma 2 to G = Gal (F'_ab/k₂) and the map G Gal(k₁/k₂) one sees that only the following two cases have to beconsidered. (a) It is possible to choose so that ^pm = 1, for some m, andG = G' x H where G' acts trivially on k₁ and H is generatedby . (b) For any m > 0 there exists a field K, F'ab K k₁ k₂is a cyclic Galois extension of degree p^m. In the first case, we let K F'_ab be the fixed field of G'.Then (A, I, ), regarded as being defined over K, has a modelover k₂. Indeed, if m = 1, then this was observed above, butwhen m > 1 the same argument applies. In the second case, let : (A, I, ) (A$$\stackrel{\¯}{\sigma}$$, I$$\stackrel{\¯}{\sigma }$$, $$\stackrel{\¯}{\sigma}$$) be an isomorphism defined over k₁ and let v ... ^p–1 = µ(R). If is replaced by for some Aut_k1((A, I, )) then is replacedby ^P. Thus, as µ(R) is finite, we may assume that ^pm–1= 1 for some m. Choose K, as in (b), to be of degree p^m overk₂. Let _m be a generator of Gal (K/k₂) whose restriction tok₁ is $$\stackrel{\¯}{\sigma }$$. Then : (A, I, ) (A^{$$\stackrel{\¯}{\sigma }$$}, I^{$$\stackrel{\¯}{\sigma}$$}, ^{$$\stackrel{\¯}{\sigma }$$} = (A^{$$\stackrel{\¯}{\sigma}$$m}, I^{$$\stackrel{\¯}{\sigma }$$m}, ^{$$\stackrel{\¯}{\sigma}$$m} is an isomorphism defined over K and v ^mpm–1, ... ^m =^pm–1 = 1, and so, by) Lemma 1, (A, I, ) has a model overk₂ which becomes isomorphic to (A, I, over K. The proof may now be completed as before. Addendum: Professor Shimura has pointed out to me that the claimon lines 25 and 26 of p. 371, viz that µ(R) is a puresubgroup of _R^*t, does not hold for all rings R. Thus this condition,which appears to be essential for the validity of the theorem,should be included in the hypotheses. It holds, for example,if µ(R) is a direct summand of µ(F).     

Exact Free Surface Flows for Shallow Water Equations I: The Incompressible Case

A comprehensive exact treatment of free surface flows governed by shallow water equations (in sigma variables) is given. Several new families of exact solutions of the governing PDEs are found and are shown to embed the well-known self-similar or traveling wave solutions which themselves are governed by reduced ODEs. The classes of solutions found here are explicit in contrast to those found earlier in an implicit form. The height of the free surface for each family of solutions is found explicitly. For the traveling or simple wave, the free surface is governed by a nonlinear wave equation, but is arbitrary otherwise. For other types of solutions, the height of the free surface is constant either on lines of constant acceleration or on lines of constant speed; in another case, the free surface is a horizontal plane while the flow underneath is a sine wave. The existence of simple waves on shear flows is analytically proved. The interaction of large amplitude progressive waves with shear flow is also studied.     

唯一分解整环上多项式不可约的一个判别法

给出了唯一分解整环上多项式不可约的一个判别法.     

唯一分解整环R上不可约多项式的一个判别准则

本获得了一个判别唯一分解整环R及其商域Q上的n次（n＞2)多项式不可约的充分条件。     

QPECgen, a MATLAB Generator for Mathematical Programs with Quadratic Objectives and Affine Variational Inequality Constraints

We describe a technique for generating a special class, called QPEC, of mathematical programs with equilibrium constraints, MPEC. A QPEC is a quadratic MPEC, that is an optimization problem whose objective function is quadratic, first-level constraints are linear, and second-level (equilibrium) constraints are given by a parametric affine variational inequality or one of its specialisations. The generator, written in MATLAB, allows the user to control different properties of the QPEC and its solution. Options include the proportion of degenerate constraints in both the first and second level, ill-conditioning, convexity of the objective, monotonicity and symmetry of the second-level problem, and so on. We believe these properties may substantially effect efficiency of existing methods for MPEC, and illustrate this numerically by applying several methods to generator test problems. Documentation and relevant codes can be found by visiting http://www.ms.unimelb.edu.au/danny/qpecgendoc.html.