Matroids with given restrictions and contractions

If M is a matroid on a set S and if X is a subset of S, then there are two matroids on X induced by M: namely, the restriction and the contraction of M onto X. Necessary and sufficient conditions are obtained for two matroids on the same set to be of this form and an analogous result is obtained when (X₁,…, X_t) is a partition of S. The corresponding results when all the matroids are binary are also obtained.     

Global restrictions on ramification in number fields

Let G be the Galois group of a number field extension. For each primep a map (p)H²(G,{±1}){±1} is defined. This local symbol has a global restriction: the product of (p) over all primes is trivial. This paper discusses how to compute (p) and gives an application to integer valued polynomials over certain quartic number fields.     

Imbedding problem with non-Abelian kernel of order p4

This paper considers the imbedding problem for numerical fields and p-groups with nonabelian kernel of order p⁴, two generators and , and defining relations =1, ^p=1, [,,]=1, and [,,]= 1. For p=2 and almost always for odd p, the Hasse principle is valid, and the problem is solvable if and only if all related local problems are solvable. Counterexamples in which the Hasse principle is not valid are constructed for some exceptional cases.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademii Nauk SSSR, Vol. 175, pp. 46–62, 1989.     

Imbedding problem with a noncommutative kernel of order p4. II

The problem of imbedding number fields is investigated for p-groups, where the kernel is a non-Abelian group of order p⁴ with two generators , and relationsIt is shown that the solvability of this problem is equivalent to the simultaneous solvability of all the collateral local problems and the collateral Abelian problem obtained by the factorization of the kernel by the derived group.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademiya Nauk SSSR, Vol. 191, pp. 101–113, 1991.     

On the m-capacitated peripatetic salesman problem with capacity restrictions

We consider a special case of the problem of finding m Hamiltonian cycles with capacity restrictions on the number of usages of the edges (m-Capacitated Peripatetic Salesman Problem or m-CPSP): the minimization and maximization 2-CPSP with edge weights chosen from an integer segment {1, q} with the edges capacities given as independent identically distributed random variables equal to 2 with probability p and 1 with probability (1 ? p). Some polynomial algorithms are proposed for 2-CPSP_min and 2-CPSP_max with average performance guarantees. In particular, when the edge weights are equal to 1 and 2, the algorithms have approximation ratios (19 ? 5p)/12 and (25 + 7p)/36 for the minimization and the maximization problem correspondingly.     

Embedding problems with ramification conditions

I want to thank Dr. J. Neukirch for his valuable remarks on an earlier version of this work and Dr. P. Bayer for her constant support during its realisation.     

LP based heuristics for the multiple knapsack problem with assignment restrictions

Starting with a problem in wireless telecommunication, we are led to study the multiple knapsack problem with assignment restrictions. This problem is NP-hard. We consider special cases and their computational complexity. We present both randomized and deterministic LP based algorithms, and show both theoretically and computationally their usefulness for large-scale problems.     

Extensions with Archimedean ramification points

A subgroup of the Galois group of an extension of an algebraic number field that is closed with respect to 2-extensions is considered. This subgroup is generated by the inertia sub-groups of the real points of the maximal real subfield. It is proved that this group is the free product of the Cantor set of cyclic groups of order 2 in the category of pro-2-groups.Translated from Matematicheskie Zametki, Vol. 14, No. 1, pp. 61–66, July, 1973.The author would like to thank L. V. Kuz'min for his guidance in this paper and E. S. Golod for his improving comments.     

Elasticity and ramification

Let A ? Bbe an extension of domains and Xbe an indeterminate over B. In this paper, we study the elasticity of atomic domains of the form A+ XB[X] where A ? Bis an integral extension. First, we study the case where A = Zand, show that, whatever B, this elasticity is infinite. Finally, we investigate the case where Ais a discrete valuation ring with quotient field Kand Bits integral closure in a finite extension of K.     

Imbedding a Filial Ring with Identity

We obtain that a uniformly bounded simple module over a high rank Virasoro algebra is a module of the intermediate series, and that a simple module with finite dimensional weight spaces is either a module of the intermediate series or a so-called GHW module.

     

Multiparameter inverse problem of approximation by functions with given supports

Let L _p (S), 0 < p < +∞, be a Lebesgue space of measurable functions on S with ordinary quasinorm ∥·∥ _p . For a system of sets {B _t |t ∈ [0, +∞) ⁿ } and a given function ψ: [0, +∞) ⁿ ↦ [ 0, +∞), we establish necessary and sufficient conditions for the existence of a function f ∈ L _p (S) such that inf {∥f − g∥ _p ^p g ∈ L _p (S), g = 0 almost everywhere on S\B _t } = ψ (t), t ∈ [0, +∞) ⁿ . As a consequence, we obtain a generalization and improvement of the Dzhrbashyan theorem on the inverse problem of approximation by functions of the exponential type in L ₂. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 8, pp. 1116–1127, August, 2006.     

Imbedding methods for integral equations with applications

During the last decade or two, significant progress has been made in the development of imbedding methods for the analytical and computational treatment of integral equations. These methods are now well known in radiative transfer, neutron transport, optimal filtering, and other fields. In this review paper, we describe the current status of imbedding methods for integral equations. The paper emphasizes new analytical and computational developments in control and filtering, multiple scattering, inverse problems of wave propagation, and solid and fluid mechanics. Efficient computer programs for the determination of complex eigenvalues of integral operators, analytical investigations of stability for significant underlying Riccati integrodifferential equations, and comparisons against other methods are described.     

On a problem of Katona on minimal completely separating systems with restrictions

Let S be a set of n elements, and k a fixed positive integer $\text{<}\text{1}\text{2}\text{n}$. Katona's problem is to determine the smallest integer m for which there exists a family $\text{A}$ = {A₁, …, A_m} of subsets of S with the following property: |_i| ? k (i = 1, …, m), and for any ordered pair x_i, x_i ∈ S (i ≠ j) there is A₁ ∈ $\text{A}$ such that x_i ∈ A₁, x_j ? A₁. It is given in this note that $\text{m = ?}\text{2n}\text{k}\text{?}\text{if}\text{1}\text{2}\text{k}{}^2\text{? 2}$.     

Efficient estimation under privacy restrictions in the disclosure problem

In the disclosure problem already collected data are disclosed only to such extent that the individual privacy is protected to at least a prescribed level. For this problem estimators are introduced which are both simple and efficient.     

Algorithms for the wafer probing scheduling problem with sequence-dependent set-up time and due date restrictions

In this paper, we consider the wafer probing scheduling problem (WPSP) to sequence families of jobs on identical parallel machines with due date restrictions. The machine set-up time is sequentially dependent on the product types of the jobs processed on the machine. The objective is to minimize the total machine workload without violating the machine capacity and job due date restrictions. The WPSP is a variation of the classical parallel-machine scheduling problem, that can be transformed into the vehicle-routing problem with time windows (VRPTW). One can therefore solve the WPSP efficiently using existing VRPTW algorithms. We apply four existing savings algorithms presented in the literature including sequential, parallel, generalized, and matching based savings, and develop three modifications called the modified sequential, the compound matching based, and the modified compound matching-based savings algorithms, to solve the WPSP. Based on the characteristics of the wafer probing process, a set of test problems is generated for testing purposes. Computational results show that the three proposed modified algorithms perform remarkably well.