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The main result of the paper is a theorem, using which a new proof of Roth’s theorem is obtained, a new solvability criterion for the matrix equation AX-YB = C is proved, a formula for a particular solution of the latter is derived, and the least of the orders of square nonsingular matrices containing a given rectangular matrix as a submatrix is determined. Bibliography: 5 titles. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a decidable case of the term semiunification problem. In our case, the arity of any functional symbol in terms equals one (with a possible exception for outer symbols of terms, for which no restrictions are imposed). We propose an algorithm constructing the most general solution of the semiunification problem. In addition, we prove an upper bound on the height of this solution; this upper bound is linear with respect to heights of terms in the initial problem. Our method reduces the problem for terms to a special system of equations in free semigroups and solves the latter system. Bibliography: 10 titles. [ABSTRACT FROM AUTHOR]

The article investigates the lower-order coefficients of parabolic equations' sufficient conditions which guarantee the stabilization of solutions of Cauchy problems in types of exponentially increasing functions. Here, the Cauchy problem is considered in the half-space.

The first and second one-dimensional boundary-value problems for parabolic equations are investigated in the case where the conjugation conditions for all required orders are not satisfied. The existence and uniqueness are proved. Estimates of solutions in classical and weighted Hölder spaces are obtained. We prove that the violation of conjugation for the given functions on the boundary of the domain at the initial-time moment causes the appearance of singular solutions. The order of singularity (as a power of t) is found for the singular solutions for t = 0. [ABSTRACT FROM AUTHOR]

The article presents estimates for degenerate elliptic differential equations. It can be divided into three parts; the first part contains auxiliary results; the second part proving priori estimates for the operator defined; and the third part being devoted to the construction of the Friedrichs extension.

The equations under consideration have the following structure: where 0 < x n < ∞, ( x 1, ..., x n−1) ∈ Ω, Ω is a bounded Lipschitz domain, $$f(0,x_n ) \equiv 0,\tfrac{{\partial f}}{{\partial u}}(0,x_n ) \equiv 0$$ is a function that is continuous and monotonic with respect to u, and all coefficients are bounded measurable functions. Asymptotic formulas are established for solutions of such equations as x n → + ∞; the solutions are assumed to satisfy zero Dirichlet or Neumann boundary conditions on ∂Ω. Previously, such formulas were obtained in the case of a ij, ai depending only on ( x 1, ..., x n−1). [ABSTRACT FROM AUTHOR]