A counterexample concerning line-free groups and complete Erdos space

We present a weakly closed, one-dimensional, line-free subgroup of the separable Banach space that is not homeomorphic to complete Erdos space. The existence of this example disproves a conjecture of Dobrowolski, Grabowski, and Kawamura.

     

Decomposability of graph -algebras

We give conditions on an arbitrary directed graph for the associated Cuntz-Krieger algebra to be decomposable as a direct sum. We describe the direct summands as certain graph algebras.

     

Set-theoretic complete intersections in characteristic

We describe a class of toric varieties which are set-theoretic complete intersections only over fields of one positive characteristic .

     

Weak axioms of choice for metric spaces

In the framework of ZF, i.e., Zermelo-Fraenkel set theory without the axiom of choice AC, we show that if the family of all non-empty, closed subsets of a metric space has a choice function, then so does the family of all non-empty, open subsets of . In addition, we establish that the converse is not provable in ZF.

We also show that the statement ``every subspace of the real line with the standard topology has a choice function for its family of all closed, non-empty subsets" is equivalent to the weak choice form ``every continuum sized family of non-empty subsets of reals has a choice function".

     

一类局部定向完备集及其范畴的性质

本文给出了局部定向完备集的概念及其在此结构下的一种新的双小于关系，从而进一步给出了一种新的连续性概念，接着讨论了局部定向完备集，连续的局部定向完备集等对象的一些性质，最后考察了三种范畴的笛卡儿闭性，并证明了范畴LDCPO是范畴ALG的反射满子范畴．     

基于利率市场化的银行贷款竞争导向定价策略研究

本文着重对两个银行之间竞争导向定价策略博弈行为进行了分析，认为在利率管制条件下，银行难以运用利率杠杆在信贷市场进行有效竞争；利率市场化之后，监管者不再对利率进行约束，银行信贷竞争的广度和深度都会随之加大。因此价格竞争将是银行信贷市场竞争的常态。     

The Twin Domination Numb er of Strong Pro duct of Digraphs

Let γ*(D) denote the twin domination number of digraph D and let D_1  D_2 denote the strong product of D_1 and D_2. In this paper, we obtain that the twin domination number of strong product of two directed cycles of length at least 2.Furthermore, we give a lower bound of the twin domination number of strong product of two digraphs, and prove that the twin domination number of strong product of the complete digraph and any digraph D equals the twin domination number of D.     

Dominant regions in noncrystallographic hyperplane arrangements

For a crystallographic root system, dominant regions in the Catalan hyperplane arrangement are in bijection with antichains in a partial order on the positive roots. For a noncrystallographic root system, the analogous arrangement and regions have importance in the representation theory of an associated graded Hecke algebra. Since there is also an analogous root order, it is natural to hope that a similar bijection can be used to understand these regions. We show that such a bijection does hold for type H₃ and for type I₂(m), including arbitrary ratio of root lengths when m is even, but does not hold for type H₄. We give a criterion that explains this failure and a list of the 16 antichains in the H₄ root order which correspond to empty regions.     

Closed manifolds coming from Artinian complete intersections

We reformulate the integrality property of the Poincaré inner product in the middle dimension, for an arbitrary Poincaré -algebra, in classical terms (discriminant and local invariants). When the algebra is -connected, we show that this property is the only obstruction to realizing it by a smooth closed manifold, in dimension . We analyse the homogeneous artinian complete intersections over realized by smooth closed manifolds of dimension , and their signatures.

     

Toader型平均的算术与调和平均界

给出了Toader型平均T[A(a,b),G(a,b)]关于调和平均H(a,b)与算术平均A(a,b)组合的精确界.作为应用,发现了几个关于第二类完全椭圆积分的精确不等式.