Small cancellation theory with a weakened small cancellation hypothesis. III. The conjugacy problem

In [1] we introduced the small cancellation condition W(4) and developed the basic theory. In this article we solve the conjugacy problem for groups with a finite W(4) presentation. Incumbent of the Lilian and George Lyttle Career Development Chair in Perpetuity, Established by Mrs. Helen Kimmelman, New York.     

Small cancellation theory with a weakened small cancellation hypothesis. I. The basic theory

We introduce a new small cancellation condition, the condition W(4), which weakens the condition C(4) & T(4), and develop the corresponding small cancellation theory. In this paper we develop the basic theory and prove a version of Greendlinger’s Lemma. In the forthcoming papers with the same title we prove the word problem and the conjugacy problem for groups having a presentation which satisfies the condition W(4).     

On theT(q)-conditions of small cancellation theory

In this paper we give a graphical method which can be used to determine whether or not a group presentation satisfies the small cancellation conditionT(q). We use this method to determine all 2- and 3-generator presentations satisfyingT(4).     

Genus and cancellation

In [14] we established a relationship between genus and localization of finitely generated torsion-free abelian by finite groups aud grnus and localization integral representation theory. In this paper we strrcly the consequences of this relationship. We prove results about the genus of groups which are analogues to results in integral representaion theory. In particular we prove non-cancellation phenomena for finitely generated groups with finite commutator subgroups.     

Free subgroups of small cancellation groups

In this paper we give a simple proof of Collin’s theorem concerning free subgroups ofC(4),T(4) groups. Our proof actually shows that a slenderT(4) presentation 〈x ₁,x ₂, …,x _n ;r〉 has a free subgroup of rank 2 provided there is a subset {a, b, c} of {x ₁,x ₂, …,x _n } with the property that any non-empty freely reduced word ina, b, c equal to 1 inG has a subword of length 2 contained in an element ofr*.     

On the size of Edge-Chromatic critical graphs

A conjecture of V.G. Vizing states that if G is a Δ-critical graph of order ? and size m, thenm ≥ 1/2(n(Δ - 1) + 3). This conjecture has been verified for Δ ≤ 4 by I.T. Jakobsen, L.W. Beineke, S. Fiorini and H.P. Yap. In this paper, we prove the conjecture for Δ = 5.     

Generalized Schur-concave Functions and Eaton Triples

Motivated by Schur-concavity, we introduce the notion of G -concavity where G is a closed subgroup of the orthogonal group O ( V ) on a finite dimensional real inner product space V . The triple ( V , G , F ) is an Eaton triple if F ² V is a nonempty closed convex cone such that (A1) Gx 7 F is nonempty for each x ε V . (A2) max g ε G ( x,gy ) = ( x,gy ) for all x, y ε F . If W := span F and H := { g | W : g ε G , gW = W } ² O ( W ), and ( W , H , F ) is an Eaton triple, then ( W , H , F ) is called a reduced triple of the Eaton triple ( V , G , F ). In this event, a characterization of the G -concavity in terms of H -concavity is obtained. Some differential characterizations of G -concavity are then given. The results are applied to Lie groups. Various matrix examples are given.     

p-adic域,p-级数域的整环子群上微积分算子的Hardy空间有界性

Ｆ．Ｓｃｈｉｐｐ和Ｗ．Ｒ．Ｗａｄｅ在［１］中证明了单位方体上Ｄｙａｄｉｃ二元微积分算子的混合Ｈａｒｄｙ空间Ｈ＃（Ｉ×Ｉ）的弱型．本文证明了ｐ ａｄｉｃ域，ｐ 级数域的整环子群上一元和二元积分算子与微积分算子的Ｈｒ（Ｇ）与Ｈ＃（Ｇ×Ｇ）（０＜ｒ１）有界性．     

Isomorphisms of the Unitriangular Groups and Associated Lie Rings for the Exceptional Dimensions

Isomorphisms between finitary unitriangular groups and those of associated Lie rings are studied. In this paper we investigate exceptional cases. Mathematics Subject Classifications (2000) 16W20, 20H25.     

Cartan型模李超代数W的二阶上同调群H2(W,F)

本文研究了有限维广义Witt李超代数W的二阶上同调群H2(W,F),其中F是一个特征P＞2的代数封闭域.通过计算W到W*的导子,得到H2(W,F)是平凡的.应用此结果,我们可得W的中心扩张是平凡的.     

Small cancellation groups and translation numbers

In this paper we prove that C(4)-T(4)-P, C(3)-T(6)-P and C(6)-P small cancellation groups are translation discrete in the strongest possible sense and that in these groups for any and any there is an algorithm deciding whether or not the equation has a solution. There is also an algorithm for calculating for each the maximum such that is an -th power of some element. We also note that these groups cannot contain isomorphic copies of the group of -adic fractions and so in particular of the group of rational numbers. Besides we show that for and groups all translation numbers are rational and have bounded denominators.

     

R4(C)中平均曲率方向平行的Bonnet曲面

本文利用[5]的方法,对R4(C)中平均曲率方向平行的Bonnet曲面引入了半测地等温 参数,并给出了一个分类结果.     

Pseudocompact groups: progress and problems

Several months ago the speaker and Jan van Mill gave a proof of this result [W.W. Comfort, J. van Mill, Extremal pseudocompact abelian groups are compact metrizable, Abstracts Amer. Math. Soc. 27 (2006) 78 (Abstract #1014-22-958); W.W. Comfort, J. van Mill, Extremal pseudocompact abelian groups are compact metrizable, Proc. Amer. Math. Soc. 135 (2007) 4039-4044]: A pseudocompact abelian group of uncountable weight admits both a proper dense pseudocompact subgroup and a strictly larger pseudocompact group topology.This presentation will describe both the necessary new details of the argument and the historical development (useful tools, special cases). Among those who contributed essentially are: K.A. Ross (1964, 1966); T. Soundararajan (1982); L.C. Robertson (1982, 1988); J. van Mill (1989); J. van Mill and H. Gladdines (1994); J. Galindo (2002).Several related unsolved problems will be cited.     

反超图的着色理论

反超图及其上色数概念是由 Ｖｉｔａｌｙ　Ｉ,Ｖｏｌｏｓｈｉｎ在文献［２］中提出来的．本文给出了点对图的概念,再将反超图的着色理论和图的连通性理论结合起来,给出了个正则反超图上色数为３的充要条件,并在此基础上得到了上色数为３的４－正则反起图的边数的一个下界．     

R4(C)中平均曲率方向平行的Bonnet曲面

本文利用[5]的方法,对R⁴(C)中平均曲率方向平行的Bonnet曲面引入了半测地等温 参数,并给出了一个分类结果.     

Ideal-Based k-Zero-Divisor Hypergraph of Commutative Rings

Let R be a commutative ring,I an ideal of R and k ≥ 2 a fixed integer.The ideal-based k-zero-divisor hypergraph HkI(R) of R has vertex set ZI(R,k),the set of all ideal-based k-zero-divisors of R,and for distinct elements x1,x2,…,xk in ZI(R,k),the set {x1,x2,…,xk} is an edge in HkI(R) if and only if x1x2…xk ∈ I and the product of the elements of any (k-1)-subset of {x1,x2,…,xk} is not in I.In this paper,we show that H3I(R) is connected with diameter at most 4 provided that x2 (∈) I for all ideal-based 3-zero-divisor hypergraphs.Moreover,we find the chromatic number of H3 (R) when R is a product of finite fields.Finally,we find some necessary conditions for a finite ring R and a nonzero ideal I of R to have H3I (R) planar.     

Cubulating small cancellation groups

We study the B(6) and B(4)-T(4) small cancellation groups. These classes include the usual C(1/6) and C(1/4)-T(4) metric small cancellation groups. We show that every finitely presented B(4)-T(4) or word-hyperbolic B(6) group acts properly discontinuously and cocompactly on a CAT(0) cube complex. We show that finitely generated infinite B(6) and B(4)-T(4) groups have codimension 1 subgroups and thus do not have property (T). We show that a finitely presented B(6) group is wordhyperbolic if and only if it contains no subgroup.     

弱闭T(N)-模的预零化子的等距映射

本文刻划了弱闭T(N)-模的预零化子间的等距映射.设u,W分别为由左连续序同态N→~N和N→~N所确定的弱闭T(N)-模, u(?),W(?)分别为u,W的预零化子,Φ为由u(?)到W(?)上的线性等距映射.若(0)*=(0)#=(0),dim(0)+≠1且min{dim(H(?)~H),dim(He(?)^H)}≥2,则存在酉算子Ui,Vi(i=1,2),使得Φ(A)=U1AV*1或Φ(A)=U2A*V2*.     

因子拟适当半群(英文)

In this paper,we investigate a class of factorisable IC quasi-adequate semigroups,so-called,factorisable IC quasi-adequate semigroups of type-（H,I）.Some characterizations of factorisable IC quasi-adequate semigroups of type-（H,I） are obtained.In particular,we prove that any IC quasi-adequate semigroup has a factorisable IC quasi-adequate subsemigroups of type-（H,I） and a band of cancellative monoids.