有限子集系的Spernet系

１９８０年，Ｋｏ－Ｗｅｉ Ｌｉｈ提出如下猜想：如果Ｆ是由Ｂ＾ｎ中固定秩的不同元素生成的序理想，那么Ｆ是Ｓｐｅｒｎｅｔ系。本文证实了当Ｆ是由Ｘ的子集Ｙ的所有相同秩的元素生成的序理想，猜想是正确的。     

关于LIH KO-WEI猜想的证明

ＬｉｎＫｏ－Ｗｅｉ［１］提出猜想：如果Ｆ是由Ｂｎ中固定秩的不同元素生成的序理想,那么Ｆ是Ｓｐｅｒｎｅｒ系［１］,黄国泰就Ｆ是由Ｘ的子集Ｙ的所有相同秩的元素生成的序理想,证实了上述猜想［２］,本文完全证明了该猜想．本文使用的概念,符号见［２］．定理设ａ...     

关于Sperner性质一个猜想的注记

设P是有限偏序集,f是P上的秩函数。P_m表示P中秩为m的元素集合。若max|P_m|=max{|A|}:A是P中的反链},则称P有Spernet性质。设a_1,…,a_kν;∈P,记F=;υ{b:a_i≤b,b∈P},称F是由a_1,…,a_k生成的序滤子。本文我们考虑的偏序集是布尔代数B~N,秩函数f(x)=|x|.K.W.LIH提出了下面猜想     

一些多项式型的有限维对合系

In this paper, starting from the combination of two in volutive systems, we consider separately some systems of polynomial functions:{I_m⁽¹⁾=B_m+R_m}_m=0^∞, {I_m⁽²⁾=B_m+S_m}_m=0^∞, {I_m⁽³⁾=B_m+T_m}_m=0^∞ and so on; and analyse carefully the sufft cient and necessary conditions of the involution of three systems of functions {I_m⁽ⁱ⁾}_m=0^∞(1≤i≤3) with general coefficients.Furthermore,we present concrete forms of the involutive systems hidden in {I_m⁽ⁱ⁾}_m=0^∞(1≤i≤3);and thus obtain six kinds of nontrivial involutive systems of functions, which include a few involutive systems discussed inthe literature. Based upon these involutive systems, we can generate a lot of new finite-dimensional Hamiltonian systems which are completely integrable in the sense of Liouville.     

一类量子Koszul 代数的Hochschild 上同调

本文利用组合的方法, 详细地计算了一类量子Koszul 代数Λ_q (q ∈ k \{0}) 的各阶Hochschild 上同调空间的维数, 清晰地刻划了代数Λ_q 的Hochschild 上同调的cup 积, 确定了代数Λ_q 的Hochschild上同调环HH^*(Λ_q) 模去幂零元生成的理想N 的结构, 证明了当q 为单位根时, HH^*(Λ_q)/N 作为代数不是有限生成的, 从而为Snashall-Solberg 猜想(即HH^*(Λ)/N 作为代数是有限生成的) 提供了更多反例.     

与I-超滤相关的基数不变量

我们对自然数ω上的每一个理想I引入了一个新的基数不变量non^**(I). 我们证明相应的I-超滤的兼纳存在性可以用non^**(I)与连续统c的等式来刻画. 具体地, 我们有如下的结果:(1) 如果non^**(I)=c, 那么任何一个由小于c个集合生成的滤子都包含在某个I-超滤中.(2) 存在一个滤子刚好可以由non^**(I)个集合生成, 但不包含在任何一个I-超滤中.(3) 任何一个由小于non^**(I)个集合生成的超滤一定是I-超滤.以上的结果是相应的P-点和Ramsey超滤的经典结论的一个推广. 我们将对一些具体的理想, 确定non^**(I)的大小, 具体地, 我们得到了non^**(Fin×Fin)=∂, non^**(εD)=cov(M)以及对不满足Fin-BW性质的理想I, 都有non^**(I)>∂.     

一类循环系的平坦性

设Ｓ是幺半群,ｘ_１,ｘ₂,…∈Ｓ且满足ｘ_i+１ｘ_i＝ｘ_i,ｉ＝１,２……ｙ是S中的任意元素,记H={(yx_i,x_i)|i=1,2,…}.设ρ(H)是S的由Ｈ生成的最小右同余,本文证明了S／ρ（Ｈ）是平坦右Ｓ－系．     

群环上的幂自由模

本文证明了：设Ｒ为ｃｈａｒＲ≠０，Ｇ为有限生成的Ａｂｅｌ群，则：Ｐ∈Ｆ＝（ＲＧ）当且仅当ｓ＞０，使得Ｐ^ｓ∈Ｆ＝（ＲＧ）．     

强Θ类算子生成的C*-代数及其K-理论

本文研究由强类算子T生成的C^*-代数,证明了C^*(T)的换子理想I(T)是一列*同构于C₀(Z⁰)上n阶矩阵代数的n齐次代数和的闭包,特别当T完全非正常时,I(T)与C₀(Z₀)K(l²)*同构。本文第二部分得到完全非正常强类算子的谱与其近似点谱相等的一些等价条件,并计算了由该类算子生成的C^*-代数的一些K群。     

具有两个生成元的SL2(C)的可解子群构造及对Fuchs系统的应用

本文给出ＳＬ₂（Ｃ）中具有两个生成元的可解子群的结构定理,并由单值群的可解性定义一类环面Ｔ²上Ｆｕｃｈｓ系统的可积性,进而研究该系统的解的一些大范围性质．     

On the Hilbert series of ideals generated by generic forms

There is a longstanding conjecture by Fröberg about the Hilbert series of the ring R∕I, where R is a polynomial ring, and I an ideal generated by generic forms. We prove this conjecture true in the case when I is generated by a large number of forms, all of the same degree. We also conjecture that an ideal generated by m’th powers of generic forms of degree d≥2 gives the same Hilbert series as an ideal generated by generic forms of degree md. We verify this in several cases. This also gives a proof of the first conjecture in some new cases.     

On ideals generated by two generic quadratic forms in the exterior algebra

Based on the structure theory of pairs of skew-symmetric matrices, we give a conjecture for the Hilbert series of the exterior algebra modulo the ideal generated by two generic quadratic forms. We show that the conjectured series is an upper bound in the coefficient-wise sense, and we determine a majority of the coefficients. We also conjecture that the series is equal to the series of the squarefree polynomial ring modulo the ideal generated by the squares of two generic linear forms.     

The Gröbner ring conjecture in one variable

We prove that a valuation domain V has Krull dimension ≤ 1 if and only if for every finitely generated ideal I of V[X] the ideal generated by the leading terms of elements of I is also finitely generated. This proves the Gröbner ring conjecture in one variable. The proof we give is both simple and constructive. The same result is valid for semihereditary rings.     

Bidendriform bialgebras, trees, and free quasi-symmetric functions

We introduce bidendriform bialgebras, which are bialgebras such that both product and coproduct can be split into two parts satisfying good compatibilities. For example, the Malvenuto-Reutenauer Hopf algebra and the non-commutative Connes-Kreimer Hopf algebras of planar decorated rooted trees are bidendriform bialgebras. We prove that all connected bidendriform bialgebras are generated by their primitive elements as a dendriform algebra (bidendriform Milnor-Moore theorem) and then is isomorphic to a Connes-Kreimer Hopf algebra. As a corollary, the Hopf algebra of Malvenuto-Reutenauer is isomorphic to the Connes-Kreimer Hopf algebra of planar rooted trees decorated by a certain set. We deduce that the Lie algebra of its primitive elements is free in characteristic zero (G. Duchamp, F. Hivert and J.-Y. Thibon conjecture).     

Toric ideals of lattice path matroids and polymatroids

White has conjectured that the toric ideal of a matroid is generated by quadric binomials corresponding to symmetric basis exchanges. We prove a stronger version of this conjecture for lattice path polymatroids by constructing a monomial order under which these sets of quadrics form Gröbner bases. We then introduce a larger class of polymatroids for which an analogous theorem holds. Finally, we obtain the same result for lattice path matroids as a corollary.     

Archimedean ordered semigroups as ideal extensions

The main result of the paper is a structure theorem concerning the ideal extensions of archimedean ordered semigroups. We prove that an archimedean ordered semigroup which contains an idempotent is an ideal extension of a simple ordered semigroup containing an idempotent by a nil ordered semigroup. Conversely, if an ordered semigroup S is an ideal extension of a simple ordered semigroup by a nil ordered semigroup, then S is archimedean. As a consequence, an ordered semigroup is archimedean and contains an idempotent if and only if it is an ideal extension of a simple ordered semigroup containing an idempotent by a nil ordered semigroup.     

Generalization of the Arrow–Barankin–Blackwell Theorem in a Dual Space Setting

In this note, we provide general sufficient conditions under which, if F is a compact [resp. w*-compact] subset of the topological dual Y* of a nonreflexive normed space Y partially ordered by a closed convex pointed cone K, then the set of points in F that can be supported by strictly positive elements in the canonical embedding of Y in Y** is norm dense [resp. w*-dense] in the efficient [maximal] point set of F. This result gives an affirmative answer to the conjecture proposed by Gallagher (Ref. 19), and also generalizes the results stated in Ref. 19 and some space specific results given in Refs. 17, 18, and 11.     

Monomial Ideals of Forest Type

As a generalization of the facet ideal of a forest, we define monomial ideal of forest type and show that monomial ideals of forest type are pretty clean. As a consequence, we show that if I is a monomial ideal of forest type in the polynomial ring S, then Stanley's decomposition conjecture holds for S/I. The other main result of this article shows that a clutter is totally balanced if and only if it has the free vertex property, and which is also equivalent to say that its edge ideal is a monomial ideal of forest type or is generated by an M sequence.     

Maximal and Minimal Semilattices on Ordered Sets

The map which takes an element of an ordered set to its principal ideal is a natural embedding of that ordered set into its powerset, a semilattice. If attention is restricted to all finite intersections of the principal ideals of the original ordered set, then an embedding into a much smaller semilattice is obtained. In this paper the question is answered of when this construction is, in a certain arrow-theoretic sense, minimal. Specifically, a characterisation is given, in terms of ideals and filters, of those ordered sets which admit a so-called minimal embedding into a semilattice. Similarly, a candidate maximal semilattice on an ordered set can be constructed from the principal filters of its elements. A characterisation of those ordered sets that extend to a maximal semilattice is given. Finally, the notion of a free semilattice on an ordered set is given, and it is shown that the candidate maximal semilattice in the embedding-theoretic sense is the free object.     

Complete intersection points on affine varieties

This paper addresses the following problem: given a commutative ring A, what is the structure of the set of “CI points,” i.e., those maximal ideals generated by dim(A) elements? When A is finitely generated over an algebraically closed field, we conjecture that this set is a countable union of closed subsets of Max(A). When A is regular of dimension ? or 3, we verify this conjecture, as well as an analogous set-theoretic conjecture.