Cohen–Macaulay Modules and Holonomic Modules Over Filtered Rings

We study Gorenstein dimension and grade of a module M over a filtered ring whose associated graded ring is a commutative Noetherian ring. An equality or an inequality between these invariants of a filtered module and its associated graded module is the most valuable property for an investigation of filtered rings. We prove an inequality G?dim M ≤ G?dim gr M and an equality grade M = grade gr M, whenever Gorenstein dimension of gr M is finite (Theorems 2.3 and 2.8). We would say that the use of G-dimension adds a new viewpoint for studying filtered rings and modules. We apply these results to a filtered ring with a Cohen–Macaulay or Gorenstein associated graded ring and study a Cohen–Macaulay, perfect, or holonomic module.     

Castelnuovo–Mumford Regularity of Associated Graded Modules and Fiber Cones of Filtered Modules

We give bounds on the Castelnuovo–Mumford regularity of the associated graded module of an arbitrary good filtration and of its fiber cone. These bounds extend previous results of Rossi–Trung–Valla and Linh.     

Modules with Nakayama’s property

Modules M _A with Nakayama’s property are studied. In particular, for a right invariant ring A, it is proved that all right A-modules satisfy Nakayama’s property if and only if the ring A is right perfect.     

Young’s Seminormal Form and Simple Modules for S n in Characteristic p

We realize the integral Specht modules for the symmetric group S _n as induced modules from the subalgebra of the group algebra generated by the Jucys–Murphy elements. We deduce from this that the simple modules for ${{\mathbb F}_p} S_n $ are generated by reductions modulo p of the corresponding Jucys–Murphy idempotents.     

Relative Flatness,Mittag–Leffler Modules,and Endocoherence

Let M _R be a right R-module over a ring R with S = End(M _R ). We study the coherence of the left S-module _S M relative to a hereditary torsion theory for the category of right R-modules. Various results are developed, many extending known results.     

Marchaud’s Inequality for Multiple Modules of Continuity in Metric Spaces

Ukrainian Mathematical Journal - For periodic functions of one variable in the metric spaces LΨ [0, 2π], we establish an analog of Marchaud’s inequality for multiple modules of...     

Computing Final Polynomials and Final Syzygies Using Buchberger’s Gröbner Bases Method

Final polynomials and final syzygies provide an explicit representation of polynomial identities promised by Hilbert’s Nullstellensatz. Such representations have been studied independently by Bokowski [2,3,4] and Whiteley [23,24] to derive invariant algebraic proofs for statements in geometry. In the present paper we relate these methods to some recent developments in computational algebraic geometry. As the main new result we give an algorithm based on B. Buchberger’s Gröbner bases method for computing final polynomials and final syzygies over the complex numbers. Degree upper bound for final polynomials are derived from theorems of Lazard and Brownawell, and a topological criterion is proved for the existence of final syzygies. The second part of this paper is expository and discusses applications of our algorithm to real projective geometry, invariant theory and matrix theory.     

The Quality of Approximation of Brun’s Algorithm in Three Dimensions

 We show that for the three-dimensional multiplicative Brun’s algorithm, the exponent of convergence is , i.e. there is a such that for almost all ,

The Quality of Approximation of Brun’s Algorithm in Three Dimensions

 We show that for the three-dimensional multiplicative Brun’s algorithm, the exponent of convergence is , i.e. there is a such that for almost all ,

Hall’s and Kőnig’s theorem in graphs and hypergraphs

We investigate the relation between Hall’s theorem and K?nig’s theorem in graphs and hypergraphs. In particular, we characterize the graphs satisfying a deficiency version of Hall’s theorem, thereby showing that this class strictly contains all K?nig–Egerváry graphs. Furthermore, we give a generalization of Hall’s theorem to normal hypergraphs.     

Extension of Talenti’s Inequality and Maximum Values Relative to Rearrangement Classes

The article starts by revisiting and extending the Talenti’s inequality where the sharpness of the extended inequality is also addressed. The process leading to the extension comprises two steps. First, an observation that the Talenti’s inequality indeed can be formulated in terms of a rearrangement class. Second, proving that the inequality holds even when the rearrangement class is replaced by a much bigger (modulo trivial cases) set namely an appropriate closure of the class. The article then continues to introduce and explore a related maximization problem, associated to the classical Poisson equation, where the admissible set is the class of rearrangements of a given function. The article briefly explains the physical interest in this optimization problem. The existence of optimal solutions is proved and the optimality conditions they satisfy are explicitly derived. The particular case where the rearrangement class is built out of a characteristic function is also discussed.     

About Gordan’s Algorithm for Binary Forms

In this article, we present a modern viewpoint on the Gordan algorithm for binary forms. The symbolic method is recast in terms of \(\mathrm {SL}(2,{\mathbb {C}})\) equivariant homomorphisms. A graphical approach is used to define Gordan’s ideal, a central tool used to obtain an integrity basis for the covariant algebra of a binary form. To illustrate the power of this method, we compute for the first time a minimal integrity basis for the covariant algebra of \(\mathrm {S}_{6}\oplus \mathrm {S}_{4}\), \(\mathrm {S}_{6}\oplus \mathrm {S}_{4}\oplus \mathrm {S}_{2}\) and for the invariant algebra of \(\mathrm {S}_{8}\oplus \mathrm {S}_{4}\oplus \mathrm {S}_{4}\).     

Serre’s Reduction of Linear Functional Systems

Serre’s reduction aims at reducing the number of unknowns and equations of a linear functional system. Finding an equivalent presentation of a linear functional system containing fewer equations and fewer unknowns can generally simplify both the study of the structural properties of the linear functional system and of different numerical analysis issues, and it can sometimes help solving the linear functional system. The purpose of this paper is to present a constructive approach to Serre’s reduction for determined and underdetermined linear functional systems.     

A Generalization of Takegoshi’s Relative Vanishing Theorem

We present a generalization of Takegoshi’s relative version of the Grauert–Riemenschneider vanishing theorem. Under some natural assumptions, we extend Takegoshi’s vanishing theorem to the case of Nakano semi-positive coherent analytic sheaves on singular complex spaces. We also obtain some new results about proper modifications of torsion-free coherent analytic sheaves.     

Cohen–Macaulay Modules in Dimension >s and Results on Local Cohomology

Let (R,𝔪) be a local ring and s ≥ ?1. Using the notion of M-sequence in dimension > s, we introduce Cohen–Macaulay modules in dimension > s. Among other things concerning Cohen–Macaulay modules in dimension > s, some finiteness results of the support and the associated primes of local cohomology modules are investigated.     

The Categories of Yetter—Drinfel’d Modules, Doi—Hopf Modules and Two-sided Two-cosided Hopf Modules

We show that the two-sided two-cosided Hopf modules are in some case generalized Hopf modules in the sense of Doi. Then the equivalence between two-sided two-cosided Hopf modules and Yetter—Drinfeld modules, proved in [8], becomes an equivalence between categories of Doi—Hopf modules. This equivalence induces equivalences between the underlying categories of (co)modules. We study the relation between this equivalence and the one given by the induced functor.     

Faraday’s Form and Maxwell’s Equations in the Heisenberg Group

In this note we present a geometric formulation of Maxwell’s equations in Carnot groups (connected simply connected nilpotent Lie groups with stratified Lie algebra) in the setting of the intrinsic complex of differential forms defined by M. Rumin. Restricting ourselves to the first Heisenberg group \mathbbH¹{\mathbb{H}^{1}}, we show that these equations are invariant under the action of suitably defined Lorentz transformations, and we prove the equivalence of these equations with differential equations “in coordinates”. Moreover, we analyze the notion of “vector potential”, and we show that it satisfies a new class of 4th order evolution differential equations.