Boundary Optimal Control for Triple Nonlinear Hyperbolic Boundary Value Problem with State Constraints

The paper is concerned with the state and proof of the solvability theorem of unique state vector solution (SVS) of triple nonlinear hyperbolic boundary value problem (TNLHBVP), via utilizing the Galerkin method (GAM) with the Aubin theorem (AUTH), when the boundary control vector (BCV) is known. Solvability theorem of a boundary optimal control vector (BOCV) with equality and inequality state vector constraints (EINESVC) is proved. We studied the solvability theorem of a unique solution for the adjoint triple boundary value problem (ATHBVP) associated with TNLHBVP. The directional derivation (DRD) of the "Hamiltonian"(DRDH) is deduced. Finally, the necessary theorem (necessary conditions "NCOs") and the sufficient theorem (sufficient conditions" SCOs"), together denoted as NSCOs, for the optimality (OP) of the state constrained problem (SCP) are stated and proved.

The Stieltjes condition and multidimensional $${\mathcal {K}}$$-moment problems

We prove a solvability theorem for the Stieltjes problem on $$\mathbb {R}^d$$ R d which is based on the multivariate Stieltjes condition $$\sum _{n=1}^\infty L(x_j^{n})^{-1/(2n)} =+\infty $$ ∑ n = 1 ∞ L ( x j n ) - 1 / ( 2 n ) = + ∞ , $$j=1,\dots ,d.$$ j = 1 , ⋯ , d . This result is applied to derive a new solvability theorem for the moment problem on unbounded semi-algebraic subsets of $$\mathbb {R}^d$$ R d .

To the orthogonal expansion theory of the solution to the Cauchy problem for second-order ordinary differential equations

Доказана теорема о разрешимости нелинейной системы уравнений относительно приближенных значений коэффициентов Чебышёва старшей производной, входящей в дифференциальное уравнение. Теорема является теоретическим обоснованием ранее предложенного приближенного метода интегрирования канонических систем обыкновенных дифференциальных уравнений второго порядка на основе ортогональных разложений с использованием многочленов Чебышёва первого рода. A solvability theorem is proved for a nonlinear system of equations with respect to the approximate Chebyshev coefficients of the highest derivative in an ordinary differential equation. This theorem is a theoretical substantiation for the previously proposed approximate method of solving canonical systems of second-order ordinary differential equations using orthogonal expansions on the basis of Chebyshev polynomials of the first kind.

Model of the Maxwell Compressible Fluid

A model of viscoelastic barotropic Maxwell fluid is investigated. The unique solvability theorem is proved for the corresponding initial-boundary value problem. The associated spectral problem is studied. We prove statements on localization of the spectrum, on the essential and discrete spectra, and on asymptotics of the spectrum.

On solvability of a nonlinear system of equations for the Fourier-Chebyshev coefficients in the problem of solving ordinary differential equations using Chebyshev series

Сформулирована и доказана теорема о разрешимости нелинейной системы уравнений относительно приближенных значений коэффициентов Фурье-Чебышёва. Теорема является теоретическим обоснованием ранее предложенного численно-аналитического метода интегрирования обыкновенных дифференциальных уравнений с использованием рядов Чебышёва. A solvability theorem for a nonlinear system of equations with respect to approximate values of Fourier-Chebyshev coefficients is formulated and proved. This theorem is a theoretical substantiation for the previously proposed numerical-analytical method of solving ordinary differential equations using Chebyshev series.

Selection in the monadic theory of a countable ordinal

A monadic formula ψ(Y) is a selector for a formula φ(Y) in a structure if there exists a unique subset P of which satisfies ψ and this P also satisfies φ. We show that for every ordinal α ≥ ωω there are formulas having no selector in the structure (α, <). For α ≤ ω1, we decide which formulas have a selector in (α, <) , and construct selectors for them. We deduce the impossibility of a full generalization of the Büchi-Landweber solvability theorem from (ω, <) to (ωω, <). We state a partial extension of that theorem to all countable ordinals. To each formula we assign a selection degree which measures “how difficult it is to select”. We show that in a countable ordinal all non-selectable formulas share the same degree.