The unit theorem for finite-dimensional algebras

The unit theorem that forms the subject of the present article, is a theorem from algebra that has a combinatorial flavour, and that originated in fact from algebraic combinatorics. Beyond a proof, we also address applications, one of which is a proof of the normal basis theorem from Galois theory.     

Algebraic prime subalgebras in simple Artinian algebras

We prove a Wedderburn-Artin type theorem for algebraic prime subalgebras in simple Artinian algebras, giving a generalized version of Yahaghi’s theorem [B.R. Yahaghi, On F-algebras of algebraic matrices over a subfield F of the center of a division ring, Linear Algebra Appl. 418 (2006) 599-613]. We also show that every semiprime left algebraic subring in a semiprime right Goldie ring must be a semiprime Artinian ring.     

Unconditionally τ-closed and τ-algebraic sets in groups

Families of unconditionally τ-closed and τ-algebraic sets in a group are defined, which are natural generalizations of unconditionally closed and algebraic sets defined by Markov. A sufficient condition for the coincidence of these families is found. In particular, it is proved that these families coincide in any group of cardinality at most τ. This result generalizes both Markov's theorem on the coincidence of unconditionally closed and algebraic sets in a countable group (as is known, they may be different in an uncountable group) and Podewski's theorem on the topologizability of any ungebunden group.     

Cayley's anticipation of a generalised Cayley-Hamilton theorem

The principal result of Cayley's famouus memoir on matrices of 1858 is his contribution to what is now known as ‘the Cayley-Hamilton theorem’. We discuss this theorem and show that prior to its publication Cayley was aware of a more general theorem, a result that he left unpublished. This theorem is associated with the binary algebraic form det (μP ? λQ) analogous to the standard characteristic polynomial det (A ? λI).     

The Fundamental Units of Algebraic Real Quadratic Function Fields

A general theorem on the fundamental unit of any algebraic quadraticfunction field K is given here; and then the fundamental unit isexhibited explicitly for sixteen types of four series of quadratic function fields K.     

Clean unital ℓ-groups

A ring with identity is said to be clean if every element can be written as a sum of a unit and an idempotent. The study of clean rings has been at the forefront of ring theory over the past decade. The theory of partially-ordered groups has a nice and long history and since there are several ways of relating a ring to a (unital) partially-ordered group it became apparent that there ought to be a notion of a clean partially-ordered group. In this article we define a clean unital lattice-ordered group; we state and prove a theorem which characterizes clean unital ?-groups. We mention the relationship of clean unital ?-groups to algebraic K-theory. In the last section of the article we generalize the notion of clean to the non-unital context and investigate this concept within the framework of W-objects, that is, archimedean ?-groups with distinguished weak order unit.     

不分明嵌入理论及其应用

本文讨论一类格上拓扑学中嵌入问题,确切说是讨论值域为fuzzy格的L不分明拓扑空间中嵌入理论及其应用.首先概述若干诸如不分明单位区间、重域构造以及格上保并映射类的代数运算等基础性成果.其次给出不分明完全正则的点式刻划与关于一致结构的著名Weil定理的不分明推广并从而建立了在不分明单位方体中一般性的嵌入定理.最后作为嵌入定理的应用,得到了不分明Urysohn度量化定理并完成了不分明Stone-Cech紧化的一般理论。     

Algebraic density property of Danilov–Gizatullin surfaces

A Danilov–Gizatullin surface is an affine surface V which is the complement of an ample section S for the ruling of a Hirzebruch surface. The remarkable theorem of Danilov and Gizatullin states that the isomorphism class of V depends only on the self-intersection number (S.S). In this paper we apply the theorem of Danilov–Gizatullin to prove that the Lie algebra generated by the complete algebraic vector fields on V coincides with the set of all algebraic vector fields of V.     

Algebraic <Emphasis Type="Italic">K</Emphasis>-theory of Gorenstein projective modules

We introduce the Gorenstein algebraic K-theory space and the Gorenstein algebraic K-group of a ring, and show the relation with the classical algebraic K-theory space, and also show the ‘resolution theorem’ in this context due to Quillen. We characterize the Gorenstein algebraic K-groups by two different algebraic K-groups and by the idempotent completeness of the Gorenstein singularity category of the ring. We compute the Gorenstein algebraic K-groups along a recollement of the bounded Gorenstein derived categories of CM-nite Gorenstein algebras.     

Cyclic cocycles on deformation quantizations and higher index theorems

We construct a nontrivial cyclic cocycle on the Weyl algebra of a symplectic vector space. Using this cyclic cocycle we construct an explicit, local, quasi-isomorphism from the complex of differential forms on a symplectic manifold to the complex of cyclic cochains of any formal deformation quantization thereof. We give a new proof of Nest-Tsygan's algebraic higher index theorem by computing the pairing between such cyclic cocycles and the K-theory of the formal deformation quantization. Furthermore, we extend this approach to derive an algebraic higher index theorem on a symplectic orbifold. As an application, we obtain the analytic higher index theorem of Connes-Moscovici and its extension to orbifolds.     

On the theorem and constants of H. Whitney

Whitney's famous theorem shows that the error of approximation to a functionf by algebraic polynomials of degree <n can be estimated by thenth order modulus of smoothness off. We show that the constants in this theorem can be taken independent ofn.     

Hyers–Ulam stability of derivations and linear functions

In this paper the following implication is verified for certain basic algebraic curves: if the additive real function f approximately (i.e., with a bounded error) satisfies the derivation rule along the graph of the algebraic curve in consideration, then f can be represented as the sum of a derivation and a linear function. When, instead of the additivity of f, it is assumed that, in addition, the Cauchy difference of f is bounded, a stability theorem is obtained for such characterizations of derivations.     

Algebraic extension of *-A operator

In this paper, we study various properties of algebraic extension of *-A operator. Specifically, we show that every algebraic extension of *-A operator has SVEP and is isoloid. And if T is an algebraic extension of *-A operator, then Weyl's theorem holds for f(T), where f is an analytic functions on some neighborhood of σ(T) and not constant on each of the components of its domain.     

The class number one problem for some totally complex quartic number fields

We prove that there are 95 non-isomorphic totally complex quartic fields whose rings of algebraic integers are generated by an algebraic unit and whose class numbers are equal to 1. Moreover, we prove Louboutin's Conjecture according to which a totally complex quartic unit εu generally generates the unit group of the quartic order Z[εu].     

Algebraic curves and the Gauss map of algebraic minimal surfaces

In this paper, we first establish a second main theorem for algebraic curves into the n-dimensional projective space. We then use it to study the ramified values for the Gauss map of the complete (regular) minimal surfaces in Rm with finite total curvature, as well as the uniqueness problem.     

Base independent algebraic cobordism

The purpose of this article is to show that the bivariant algebraic A-cobordism groups considered previously by the author are independent of the chosen base ring A. This result is proven by analyzing the bivariant ideal generated by the so called snc relations, and, while the alternative characterization we obtain for this ideal is interesting by itself because of its simplicity, perhaps more importantly it allows us to easily extend the definition of bivariant algebraic cobordism to divisorial Noetherian derived schemes of finite Krull dimension. As an interesting corollary, we define the corresponding homology theory called algebraic bordism. We also generalize projective bundle formula, the theory of Chern classes, the Conner–Floyd theorem and the Grothendieck–Riemann–Roch theorem to this setting. The general definitions of bivariant cobordism are based on the careful study of ample line bundles and quasi-projective morphisms of Noetherian derived schemes, also undertaken in this work.     

Elementary proofs of two fundamental theorems of B. Segre without using the Hasse-Weil theorem

An interesting bound on the number of points of a plane algebraic curve C of PG(2, q) is obtained, without using the deep theorem of Hasse-Weil. This bound is used to prove a well-known theorem by Segre on complete k arcs in PG(2, q), q even.     

The colorful Helly theorem and colorful resolutions of ideals

We demonstrate that the topological Helly theorem and the algebraic Auslander-Buchsbaum theorem may be viewed as different versions of the same phenomenon. Using this correspondence we show how the colorful Helly theorem of I. Barany and its generalizations by G. Kalai and R. Meshulam translate to the algebraic side. Our main results are algebraic generalizations of these translations, which in particular give a syzygetic version of Helly’s theorem.     

On the algebraic theory of scattering

Within the context of the algebraic theory for simple quantum mechanical potential scattering, we establish existence and completeness of generalized wave operators for a large class of long-range potential scattering problems. Our approach utilizes a priori knowledge of the spectral properties of the scattering Hamiltonian and an algebraic theorem on the uniqueness of a particular Euclidean group representation.     

S-unit points on analytic hypersurfaces

In analogy with algebraic equations with S-units, we shall deal with S-unit points in an analytic hypersurface, or more generally with values of analytic functions at S-unit points.After proving a general theorem, we shall give diophantine applications to certain problems of integral points on subvarieties of . Also, we shall prove an analogue of a theorem of Masser, important in Mahler's method for transcendence.In the course of the proofs we shall also develop a theory for those algebraic subgroups of whose Zariski closure in An contains the origin. Among others, we shall prove a structure theorem for the family of such subgroups contained in a given analytic hypersurface, obtaining conclusions similar to the case of algebraic varieties.