Infinitesimal Lifting and Jacobi Criterion for Smoothness on Formal Schemes

This a first step to develop a theory of smooth, étale, and unramified morphisms between Noetherian formal schemes. Our main tool is the complete module of differentials, which is, a coherent sheaf whenever the map of formal schemes is of pseudofinite type. Among our results, we show that these infinitesimal properties of a map of usual schemes carry over into the completion with respect to suitable closed subsets. We characterize unramifiedness by the vanishing of the module of differentials. Also we see that a smooth morphism of Noetherian formal schemes is flat and its module of differentials is locally free. The article closes with a version of Zariski's Jacobian criterion.     

On Algorithmic Equi-Resolution and Stratification of Hilbert Schemes

Given an algorithm for resolution of singularities that satisfiescertain conditions (‘a good algorithm’), naturalnotions of simultaneous algorithmic resolution, and of equi-resolution,for families of embedded schemes (parametrized by a reducedscheme T) are defined. It is proved that these notions are equivalent.Something similar is done for families of sheaves of ideals,where the goal is algorithmic simultaneous principalization.A consequence is that given a family of embedded schemes overa reduced T, this parameter scheme can be naturally expressedas a disjoint union of locally closed sets T_j, such that theinduced family on each part T_j is equi-resolvable. In particular,this can be applied to the Hilbert scheme of a smooth projectivevariety; in fact, our result shows that, in characteristic zero,the underlying topological space of any Hilbert scheme parametrizingembedded schemes can be naturally stratified in equi-resolvablefamilies. 2000 Mathematics Subject Classification 14E15, 14D99.     

Morphisms of the Heat Equation

In this article we consider a certain class of mappings between Riemannian manifolds of the type M × R^{+ *}, which preserve two objects associated to the heat equation. First we show that maps which pull back local solutions of the heat equation to local solutions of the heat equation, called heat equation morphisms have to be the product of a homothetic submersion and an affine map of R^{+ *}. Then using the above characterisation, we study maps which pull back the heat kernel to the heat kernel. We call such maps heat kernel morphisms. We show in Theorem 3 that, in the case of compact manifolds, a map : M × M × R^{+ *} N × N × R^{+ *} of the form (x,y,t) = ( (x), (y),h(t)), with surjective, is a heat kernel morphism if and only if is a homothetic covering of N()-sheets and constant dilation such that N() = ^m (m = dim M) and h(t) = ²t. In particular, if is bijective then it must be an isometry and h(t) = t. A similar problem was considered from a different point of view in [6].     

Heart of Irreducible Morphisms of Bounded Complexes

In [9 Giraldo , H. , Merklen , H. ( 2009 ). Irreducible morphisms of categories of complexes . Journal of Algebra 321 : 2716 – 2736 .[Crossref], [Web of Science ®] , [Google Scholar]] Giraldo and Merklen studied irreducible morphisms in the categories 𝒞(𝒜) and D^?(Λ), where 𝒞(𝒜) is the category of complexes over an abelian Krull–Schmidt category 𝒜 and D^?(Λ) is the derived category of the bounded above complexes of finite generate left modules, over an Artin algebra Λ. In this work, we continue the study of irreducible morphism having one finite irreducible truncation.     

Characterization of Quasi-Coherent Modules that are Module Schemes

Let R be a commutative ring with unit, and let E be an R-module. We say the functor of R-modules E, defined by E(B) = E ? _R B, is a quasi-coherent R-module, and its dual E* is an R-module scheme. Both types of R-module functors are essential for the development of the theory of the linear representations of an affine R-group. We prove that a quasi-coherent R-module E is an R-module scheme if and only if E is a projective R-module of finite type, and, as a consequence, we also characterize finitely generated projective R-modules.     

关于群胚作用和李双代数胚态射

在这篇文章中，我们讨论了李双代数胚之间的态射，得到了一些李双代数胚之间态射的性质．研究了泊松群胚在泊松流形上的泊松作用，以及这个泊松作用与被作用流形的切李双代数胚到作用泊松群胚的切李双代数胚之间的态射的关系，得到了一些有用的结论。     

On the Composite of Three Irreducible Morphisms in the Fourth Power of the Radical

We study here the nonzero composite of three irreducible morphisms between indecomposable modules lying in the fourth power of the radical.     

某些Banach空间的有限阶光滑点和强光滑点（英）

本文给出l_∞(X)以及L(l₁(X),Y),L(X,l_∞(Y))和L(X,c₀(Y))的单位球的有限阶光滑点和强光滑点的充要条件，这里X和Y都是任意的Banach空间.特别地，本文给出这些空间的单位球的光滑点和强光滑点的充要条件.     

Weak Density of Smooth Maps in W 1, 1(M,N) for Non-Abelian π1(N)

We prove that smooth maps are dense in the sense of biting convergence in W ^{1, 1}(M, N) when M and Nare compact Riemannian manifolds and N is closed.     

Reducibility of Punctual Hilbert Schemes of Cone Varieties

In this short note we show that for any pair of positive integers (d, n) with n > 2 and d > 1 or n = 2 and d > 4, there always exist projective varieties X ? ? ^N of dimension n and degree d and an integer s ₀ such that Hilb ^s (X) is reducible for all s ≥ s ₀. X will be a projective cone in ? ^N over an arbitrary projective variety Y ? ? ^N?1. In particular, we show that, opposite to the case of smooth surfaces, there exist projective surfaces with a single isolated singularity which have reducible Hilbert scheme of points.     

K—very Smooth Banach Spaces

We introduce the notion of K-very smoothness which is a generalization of very smoothness in Banach spaces. A necessary and sufficient condition for a Banach space to be K-very smooth is obtained. We also consider some relations between K-very smoothness and other geometrical notions.     

Cohomology of Noncommutative Hilbert Schemes

Noncommutative Hilbert schemes, introduced by M. V. Nori, parametrize left ideals of finite codimension in free algebras. More generally, parameter spaces of finite-codimensional submodules of free modules over free algebras are considered. Cell decompositions of these varieties are constructed, whose cells are parametrized by certain types of forests. Asymptotics for the corresponding Poincaré polynomials and properties of their generating functions are discussed. Presented by P. Littleman Mathematics Subject Classifications (2000) Primary: 16G20; secondary: 14D20.     

Secret Sharing Schemes with Detection of Cheaters for a General Access Structure

In a secret sharing scheme, some participants can lie about the value of their shares when reconstructing the secret in order to obtain some illicit benefit. We present in this paper two methods to modify any linear secret sharing scheme in order to obtain schemes that are unconditionally secure against that kind of attack. The schemes obtained by the first method are robust, that is, cheaters are detected with high probability even if they know the value of the secret. The second method provides secure schemes, in which cheaters that do not know the secret are detected with high probability. When applied to ideal linear secret sharing schemes, our methods provide robust and secure schemes whose relation between the probability of cheating and the information rate is almost optimal. Besides, those methods make it possible to construct robust and secure schemes for any access structure.     

Invariant hypercomplex structures and algebraic curves

We show that $U(k)$-invariant hypercomplex structures on (open subsets) of regular semisimple adjoint orbits in $\mathfrak{g}\mathfrak{l}(k,\mathbb{C})$ correspond to algebraic curves C of genus ${(k-1)}^2$, equipped with a flat projection $\pi :C\to {\mathbb{P}}^1$ of degree k, and an antiholomorphic involution $\sigma :C\to C$ covering the antipodal map on ${\mathbb{P}}^1$.     

On Prebox Module Topologies

Let R be a complete topological division ring whose topology is determined by a real-valued valuation, and let M be a vector space over R. It is proved that M admits a Hausdorff module topology preceding the box topology in the lattice of all module topologies if and only if the dimension of the vector space M over R is a measurable cardinal.     

同调光滑连通上链DG代数的一个注记

本文给出了有关同调光滑连通上链微分分次(简称DG)代数的两个重要结论.具体地说,当A是同调光滑连通上链DG代数且其同调分次代数H(A)是诺特分次代数时,证明D_(fg)(A)中的任意Koszul DG A-模都是紧致的.另外,当A是Kozul连通上链DG代数且其同调分次代数H(A)是有平衡对偶复形的诺特分次代数时,证明A的同调光滑性质等价于D_(fg)(A)=D~c(A).     

Fusion Relation in Products of Association Schemes

 Fusion relations between the association schemes obtained by direct product and wreath product are established via a study of their matrix representations. The character table of the scheme obtained by the wreath product is described and some algebraic properties of the products are derived. Received: May 7, 1999 Final version received: September 24, 1999 RID="*" ID="*" 1991 Mathematics Subject Classification. Primary 05E30; Secondary 05B99 RID="*" ID="*" Supported in part by Com ²MaC-KOSEF, POSTECH, Korea Acknowledgments. The author is indebted to an anonymous referee who provided the complete proof of Theorem 4.2.     

A Characterization of Association Schemes from Affine Spaces

We characterize theassociation schemes from affine spaces as the association schemesin which all relations are equivalence relations (when unitedwith the identity relation). The schemes from affine spaces ofdimension at least three are counterexamples of a conjectureof A. V. Ivanov [Problem 1.3]I on amorphic schemes.     

On a Class of Non-commutative Imprimitive Association Schemes of Rank 6

Many facts about group theory can be generalized to the context of the theory of association schemes. In particular, association schemes with fewer than 6 elements are all commutative. While there is a nonabelian group with 6 elements which is unique up to isomorphism, there are infinitely many isomorphism classes of non-commutative association schemes with 6 elements. All examples previously known to us are imprimitive, and fall into three classes which are reasonably well understood. In this paper, we construct a fourth class of noncommutative, imprimitive association schemes of rank 6.