Universally concordant Galois extensions

A Galois extension is called universally concordant of period q, if for any imbedding problem of this extension whose kernel is an Abelian group of period q the concordance condition is satisifed. A necessary and sufficient condition is given for the imbeddability of one universally concordant extension into another. For a universally concordant extension of period of an algebraic number field containing no roots of 1 of degrees p₁, ..., p_m the solvability of any imbedding problem with solvable kernel of period q is proved.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 71, pp. 133–152, 1977.     

On the imbedding problem for local fields

The imbedding problem of local fields is considered for the case where the whole of the group is a p-group having as many generators as the Galois group of the extension and the extension consists of a primitive root of 1 of degree equal to the period of the kernel. It is proved that it is necessary and sufficient for the solvability of this problem that a concordance condition (and even a weaker condition) be satisfied (see [4]).Translated from Matematicheskie Zametki, Vol. 12, No. 1, pp. 91–94, July, 1972.The author is thankful to A. V. Yakovlev for his valuable advice.When this article was in press, the author proved that Theorem 1 is valid even without Condition IV. He has also found an example showing that Condition III cannot be discarded.     

Completely solvable imbedding problems with Abelian kernel for local fields

The imbedding problem for p-groups is considered in which the fields are assumed to be local and the kernel commutative. Additional conditions are investigated under which a solvable imbedding problem has a field as solution. Sufficient conditions are found for such solvability in the form of inequalities imposed on the number of generators of certain groups.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 75, pp. 67–73, 1978.     

The Brauer imbedding problem for commutative rings

The imbedding problem with Abelian kernel in the Galois theory of commutative rings is considered. A necessary and sufficient condition for the solvability of the Brauer imbedding problem for commutative rings is found. The group of equivalence classes of imbeddings for given Abelian kernel and the subgroup of semidirect imbeddings are studied.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 57, pp. 31–50, 1976.     

On Finite Markov Chain Imbedding and Its Applications

The finite Markov Chain Imbedding technique has been successfully applied in various fields for finding the exact or approximate distributions of runs and patterns under independent and identically distributed or Markov dependent trials. In this paper, we derive a new recursive equation for distribution of scan statistic using the finite Markov chain imbedding technique. We also address the problem of obtaining transition probabilities of the imbedded Markov chain by introducing a notion termed Double Finite Markov Chain Imbedding where transition probabilities are obtained by using the finite Markov chain imbedding technique again. Applications for random permutation model in chemistry and coupon collector’s problem are given to illustrate our idea.     

A case of imbedding problem with a solvable kernel

Journal of Mathematical Sciences - It is shown for the solution of the imbedding problem of algebraic number fields with a finite solvable kernel one can take a field if the orders of the kernel...     

Invariant imbedding and multiple shooting for the solution of unstable linear boundary value problems

Invariant imbedding has been used to solve unstable linear boundary value problems for a few years. First this method is derived using the theory of characteristics; there the boundary value problem has to be imbedded in a problem of double dimension. If the corresponding Riccati equation has a critical length, one has to repeat the algorithm. A relation between this repeated invariant imbedding and multiple shooting is shown. In examples invariant imbedding, repeated invariant imbedding, multiple shooting and the superposition principle are compared.     

A finite-element capacitance matrix method for exterior Helmholtz problems

Summary. We introduce an algorithm for the efficient numerical solution of exterior boundary value problems for the Helmholtz equation. The problem is reformulated as an equivalent one on a bounded domain using an exact non-local boundary condition on a circular artificial boundary. An FFT-based fast Helmholtz solver is then derived for a finite-element discretization on an annular domain. The exterior problem for domains of general shape are treated using an imbedding or capacitance matrix method. The imbedding is achieved in such a way that the resulting capacitance matrix has a favorable spectral distribution leading to mesh independent convergence rates when Krylov subspace methods are used to solve the capacitance matrix equation. Received May 2, 1995     

On the Eigen-value Problem for Elliptic Systems Under Natural Growth Condition: the Super Limit Cases

In this paper, we consider a quasilinear elliptic eigenvalue problem. For the unbounded coefficients, we allow the eigen exponent greater than the Sobolev imbedding critical exponent; for the equations, we also allow the coefficient of suitable smallness condition greater than 1.     

嵌入定理与代数数域上的大筛法

<正> 本文把数理方程研究中常用的嵌入定理稍作推广,应用到代数数域上来,并把[4]中第四章的定理4.2和[1,5]中的均值定理推广到代数数域上. 为此,先介绍一些符号与约定,基本上采自[2]. 设K为-n次代数数域,按通常的记号,记作n=r_1+2r_2.以Z_k表K中的整数环. 1.设为一理想,如α,β∈Z_k,|(α-β),则记α≡β(mod ).按此可把K中的整数分类,其类数为N.Z_k中与互素的整数在上述分类中占住类数为     

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.     

Imbedding problem with given localizations and ramification restrictions

For a solvable imbedding problem (L/K,G,A) of a number field with Abelian kernel A and a finite set of points S of the field K, a finite set T of points of the field K, is found which has the following property: for any solvable imbedding problem with given localizations, corresponding to the problem (L/K,G,A), there exists a solution which is unramified outside of SuT.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 57, pp. 85–99, 1976.     

Discrete invariant imbedding for singular boundary value problems with a regular singularity

We describe a discrete invariant imbedding method for solving a two point boundary value problem in the interval [0,b] for a linear second order ordinary differential equation with a singularity of the first kind at x = 0. By employing the series expansion on (0, δ], where δ is near the singularity, we first replace it by a regular problem on some interval [δ, b]. The discrete invariant imbedding method is then described to solve the problem over the reduced interval. The stability analysis of the method is discussed. Some model problems are solved, and the numerical results compared with those of other methods.     

A one-sweep method for linear elliptic equations over irregular domains

The determination of the configuration of equilibrium in a number of problems in mechanics and structures such as torsion, deflection of elastic membranes,etc., involve the solution of variational problems defined over irregular regions. This problem, in turn, may be reduced to the solution of elliptic differential equations subject to boundary conditions. In this paper, we study a method for the solution of such a problem when the region is of irregular shape. The method consists in solving the problem over a larger, imbedding, rectangular domain subject to appropriate constraints such as to satisfy the conditions of the original problem at the boundary. In this paper, we introduce the constraints by considering appropriate factors on the Green's function of the auxiliary problem. A conveniently discretized version of the problem is then treated by invariant imbedding, yielding some earlier results plus some new ones, namely, a direct one-sweep procedure that minimizes storage requirements. In addition, the present solution appears to be very convenient when the solution is required at a limited number of points. The derivations are specialized to Laplace's equation, but the method can be applied readily to general systems of second-order elliptic equations with no essential modifications. Finally, the existence of the necessary matrices in the imbedding equations is established.     

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。     

Approximate method for the numerical solution of singular perturbation problems

We present an approximate method for the numerical solution of linear singularly perturbed two point boundary value problems in ordinary differential equations with a boundary layer on the left end of the underlying interval. It is motivated by the asymptotic behavior of singular perturbation problems. The original problem is divided into inner and outer region problems. The reduced problem is solved to obtain the terminal boundary condition. Then, a new inner region problem is created and solved as a two point boundary value problem. In turn, the outer region problem is also modified and the resulting problem is efficiently treated by employing the trapezoidal formula coupled with discrete invariant imbedding algorithm. The proposed method is iterative on the terminal point. Some numerical experiments have been included to demonstrate its applicability.     

Factorization and imbedding for general linear boundary value problems

A new direction in the theory of general linear boundary value problems is explored. The starting point is an explicit Volterra factorization of the Green's matrix (and related kernels) associated with the problem. This result leads to (1) imbedding of the boundary value problems, (2) initial value algorithms for their solution, and (3) comparison theorems relating two different boundary value problems with a common boundary condition. Extensions and connections with earlier work in this area are presented.     

The unified approach in a semi-infinite atmosphere

The unified approach of invariant imbedding is extended to the case of a semi-infinite atmosphere. The integral equation satisfied by the reflection function from a semi-infinite atmosphere is derived by virtue of the approach. For stationary and non-stationary radiation fields, the equations obtained in this article coincide with those already obtained.