On Browkin’s conjecture about the elements of order five in <Emphasis Type="Italic">K</Emphasis><Subscript>2</Subscript>(ℚ)

Based on the work of Lenstra, a succinct proof of Browkin’s conjecture about the elements of order five in K ₂(ℚ) is given. This work was supported by the National Natural Science Foundation of China (Grant No. 10371061).     

Neither G9（Q） nor G11（Q） Is a Subgroup of K2（Q）

It is proved that neither G9(Q) nor G11(Q) is a subgroup of K2(Q) which confirms two special cases of a conjecture proposed by Browkin, J. (Lecture Notes in Math., 966, Springer-Verlag, New York, Heidelberg, Berlin, 1982, 1-6).     

Some Elements of Finite Order in K2Q

Let K2 be the Milnor functor and let Фn （x）∈ Q[X] be the n-th cyclotomic polynomial. Let Gn（Q） denote a subset consisting of elements of the form {a, Фn（a）}, where a ∈ Q^＊ and {, } denotes the Steinberg symbol in K2Q. J. Browkin proved that Gn（Q） is a subgroup of K2Q if n = 1,2, 3, 4 or 6 and conjectured that Gn（Q） is not a group for any other values of n. This conjecture was confirmed for n =2^T 3S or n = p^r, where p ≥ 5 is a prime number such that h（Q（ζp）） is not divisible by p. In this paper we confirm the conjecture for some n, where n is not of the above forms, more precisely, for n = 15, 21,33, 35, 60 or 105.     

某些K_2O_F的结构(英文)

本文研究二次数域 Ｆ＝ 的 Ｋ２ＯＦ结构,其中 ｄ－３ ｍｏｄ ９和 ｄ ≠－３．找到了关于Ｆ＝的Ｋ２ＯＦ的３阶元和Ｆ＝的Ｋ２ＯＦ的生成元,推广Ｔ Ｂａｓｓ和 Ｔａｔｅ的一个定理和给出了 Ｆ＝ 的 Ｋ２ＯＦ的结构以及 ＳＬｎ（ＯＦ）（ｎ≥３）的表示关系．     

A conjecture on a class of elements of finite order in K2Fp

For a local field F the finite subgroups of K₂ F are expressed by a class of special elements of finite order, which makes a famous theorem built by Moore, Carroll, Tate and Merkurjev more explicit and also disproves a conjecture posed by Browkin.     

On K 2-group of a formal matrix ring

Let S be a formal matrix ring, T the subring consisting of all diagonal elements, I the set consisting of all off-diagonal elements. Then I is a split radical ideal under certain conditions. In this paper, we show that K2 (S)■K2 (T) ? K2 (S,I), and a presentation of K2 (S,I) is given.     

Q(6~(1/2))上的定幺模格的分类

利用推广的邻格方法,完成了Q(6~(1/2))上秩4的在一个阿基米德除子上正定,在另一阿基米德除子上负定的所有幺模格种的分类.     

On a conjecture about orders of products of elements in the symmetric group

For any $a,b,c,n\in \mathbb{N}$ with $1<a,b,c\le n?2$, then there exist $\alpha ,\beta \in S_n$ such that $o(\alpha )=a$, $o(\beta )=b$ and $o(\alpha \beta )=c$. This is a conjecture of Stefan Kohl and which is closely related to problem on covers of the complex projective line. In this note we prove the conjecture is true.     

On Jackson's theorem in the space ℓ2(ℤ 2 n )

Estimates of Jackson's constants in the space ℓ₂(ℤ ₂ ⁿ ) are given for the case of approximation by sums of subspaces on which irreducible representations of the isometry group of (ℤ ₂ ⁿ ) act and for the case in which the modulus of continuity is defined using generalized translations. Coding theory results on efficiency estimates for binaryd-codes with respect to the Hamming distance are used. Translated fromMatematicheskie Zametki, Vol. 60, No. 3, pp. 390–405, September, 1996.     

The order of elements in Sylow p-subgroups of the symmetric group

Define a random variable ξ_n by choosing a conjugacy class C of the Sylow p-subgroup of S_pn by random, and let ξ_n be the logarithm of the order of an element in C. We show that ξ_n has bounded variance and mean order log n /log p +O(1), which differs greatly from the average order of elements chosen with equal probability. This revised version was published online in June 2006 with corrections to the Cover Date.     

$H(2)$-Unknotting Number of a Knot

An $H(2)$-move is a local move of a knot which is performed by adding a half-twisted band. It is known an $H(2)$-move is an unknotting operation. We define the $H(2)$-unknotting number of a knot $K$ to be the minimum number of $H(2)$-moves needed to transform K into a trivial knot. We give several methods to estimate the $H(2)$-unknotting number of a knot. Then we give tables of $H(2)$-unknotting numbers of knots with up to 9 crossings.     

广义逆A_(T,S)~(2)的一种计算方法

本文给出了利用特征多项式求矩阵广义逆AT,S(2)的一种计算方法,并由此得到了加权M-P逆AM,N+、M-P逆A+、Drazin逆Ad及群逆A9的相应计算方法,推广了文献[2]的结果.     

Finite groups in which elements of the same order outside the center are conjugate

We prove that if G is a finite group in which the elements of the same order outside the center are conjugate,then either G is abelian or G(?)S_3.     

On (2, 3)-Generation of Low-Dimensional Symplectic Groups Over the Integers

We prove that the group Sp₈(?) is generated by an involution and an element of order 3, while Sp₆(?) is not.     

Deforming abelian SU(2)-representations of knot groups

The aim of this paper is to generalize a theorem of C. D. Frohman and E. P. Klassen ([FK91]) concerning deformations of abelian SU(2)-representations of knot groups into non-abelian representations. The proof of our main theorem makes use of a generalization of a result of X.-S. Lin ([Lin92]) which should be interesting in itself. Received: December 1, 1997