Recurrent relations for the solutions of an infinite system of linear algebraic equations

We obtain recurrent relations for bounded solutions of the system of equations $$X_k - \sum\limits_{n = 0}^\infty {\frac{{(k + n)!}}{{k!n!}}} \alpha ^{k + n + 1} x_n = f_{k,} k = 0,1,..., \alpha \in (0,1/2),$$ with right-hand sides {f _k } _k=0 ^∞ ={δ _kj } _k=0 ^∞ ,j=0,1,..., where δ _kj is the Kronecker symbol.     

Principles of the theory of two-dimensional infinite systems of algebraic equations

We investigate infinite systems of algebraic equations of the form

On solutions of an infinite system of singular integral equations

Using the classical Schauder fixed point principle we prove an existence result concerning an infinite system of singular integral equations. The obtained result is applied to establish the solvability of an infinite system of differential equations of fractional order.     

An infinite algebraic system in the irregular case

We obtain sufficient conditions for the nontrivial solvability of systems of the form $$ \phi _i = b_i + \lambda _i \sum\limits_{j = 0}^\infty {a_{i - j} \phi _j ,i \in \mathbb{Z}_ + \underline{\underline {def}} \{ 0,1,2...,n,...\} ,} $$ and of the corresponding homogeneous systems. It is assumed that the sequences b = (b ₀, b ₁, b ₂, …) and λ = (λ ₀, λ ₁, λ ₂, …) and the Toeplitz matrix A = (a _i?j ) satisfy the conditions $$ \begin{gathered} a_j \geqslant 0,j \in \mathbb{Z},\sum\limits_{j = - \infty }^\infty {a_j = 1,} \sum\limits_{j = - \infty }^\infty {|j|a_j < \infty ,\sum\limits_{j = - \infty }^\infty {ja_j < 0,} } \hfill \\ b_j \geqslant 0,j \in \mathbb{Z},\sum\limits_{j = 0}^\infty {b_j = \infty ,} 1 \leqslant \lambda _i \leqslant \left( {\sum\limits_{j = - \infty }^i {a_j } } \right)^{ - 1} ,i \in \mathbb{Z}_ + . \hfill \\ \end{gathered} $$ . Under these conditions, we construct bounded solutions of homogeneous and inhomogeneous systems of the form indicated above.     

Solution of polynomial equations in the field of algebraic numbers

A method of solving polynomial equations in a ring D[x] is described, where D is an arbitrary order of field ?(ω) and ω is an algebraic integer number.     

The optimal pursuit problem reduced to an infinite system of differential equations

The optimal game problem reduced to an infinite system of differential equations with integral constraints on the players’ controls is considered. The goal of the pursuer is to bring the system into the zeroth state, while the evader strives to prevent this. It is shown that Krasovskii's alternative is realized: the space of states is divided into two parts so that if the initial state lies in one part, completion of the pursuit is possible, and if it lies in the other part, evasion is possible. Constructive schemes for devising the optimal strategies of the players are proposed, and an explicit formula for the optimal pursuit time is derived.     

Solutions of the stationary Navier-Stokes system of equations with an infinite Dirichlet integral

In unbounded domains of the three-dimensional Euclidean space, having several exits _i at infinity of a sufficiently general form, one finds the solutions of the stationary Navier-Stokes system, equal to zero on the boundary of the domain , having arbitrary flow rates d_i through each exit _i, i=1,..., , and having an unbounded Dirichlet integral . One gives sufficient conditions for the existence of a solution.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 115, pp. 251–263, 1982.     

Operator part of infinite system of differential equations

Let T be a differential operator in a Hilbert space generated by a first-order infinite system of an ordinary linear differential expression, which is subject to infinitely many boundary conditions. We solve completely for y from Ty = g. The main tools involved are operator parts of closed linear manifolds, which are closely related to generalized inverses.     

Solution of general ordinary differential equations using the algebraic theory approach

The algebraic theory for numerical methods, as developed by Herrera [3–7], provides a broad theoretical framework for the development and analysis of numerical approximations. To this point, the technique has only been applied to ordinary differential equations with constant coefficients. The present work extends the theory by developing a methodology for equations with variable coefficients. Approximation of the coefficients by piecewise polynomials forms the foundation of the approach. Analysis of the method provides firm error estimates. Furthermore, the analysis points to particular procedures that produce optimal accuracy. Example calculations illustrate the computational procedure and verify the theoretical convergence rates.     

Differential–algebraic equations in multibody system modeling

Numerical methods for the efficient integration of both stiff and nonstiff equations of motion of multibody systems having the form of differential-algebraic equations (DAE) of index 3 are discussed. Linear multi-step ABM and BDF methods are considered for the non-iterational integration of nonstiff DAE. The Park method is proposed for integration of stiff equations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Well-posedness of an infinite system of partial differential equations modelling parasitic infection in an age-structured host

We study a deterministic model for the dynamics of a population infected by macroparasites. The model consists of an infinite system of partial differential equations, with initial and boundary conditions; the system is transformed in an abstract Cauchy problem on a suitable Banach space, and existence and uniqueness of the solution are obtained through multiplicative perturbation of a linear C₀-semigroup. Positivity and boundedness are proved using the specific form of the equations.     

Cluster algebraic interpretation of infinite friezes

Originally studied by Conway and Coxeter, friezes appeared in various recreational mathematics publications in the 1970s. More recently, in 2015, Baur, Parsons, and Tschabold constructed periodic infinite friezes and related them to matching numbers in the once-punctured disk and annulus. In this paper, we study such infinite friezes with an eye towards cluster algebras of type D and affine A, respectively. By examining infinite friezes with Laurent polynomial entries, we discover new symmetries and formulas relating the entries of this frieze to one another. Lastly, we also present a correspondence between Broline, Crowe and Isaacs’s classical matching tuples and combinatorial interpretations of elements of cluster algebras from surfaces.     

Solution of an algebraic equation using an irrational iteration function

It is proved that, for the choice z _n ^[n] = ?a ₁ of the initial approximation, the sequence of approximations z _n ^[i+1] = φ _n (z _n ^[i] ), [i] = 0, 1, 2, ..., of a solution of every canonical algebraic equation with real positive roots which is of the form $$P_n (z) = z^n + a_1 z^{n - 1} + a_2 z^{n - 2} + \ldots + a_n = 0, n = 1,2, \ldots ,$$ where the sequence is generated by the irrational iteration function φ _n (z) = (z ⁿ ? P _n (z))^1/n , converges to the largest root z _n . Examples of numerical realization of the method for the problem of determining the energy levels of electron systems of a molecule or a crystal are presented. The possibility of constructing similar irrational iteration functions in order to solve an algebraic equation of general form is considered.