An inverse spectral problem is studied for Sturm – Liouville operators on arbitrary compact graphs with standard matching conditions in internal vertices. A uniqueness theorem of recovering operator’s coefficients from spectra is proved.
This article considers finite closed n-loops of the extended hyperbolic plane H2. The paper deals with topological and metric properties of the finite closed 3(4)-loops. Pasha statement analogues have been also obtained. We proved the existence of two types 4-loops and convexity of the plain 4-loop.
For an optimal control problem with a linear differential equation in Hilbert space and quadratic criteria necessary and sufficient conditions of control functions optimality and approximate formulas of the expansions of these functions in eigenfunctions of the control system operator have been obtained.
An analogue of Jordan – Dirichlet theorem is established of convergence of the expansions in eigen functions of the operator Ly = αy′(x) − y′(1 − x) with the boundary condition U(y) = ay(0) + by(1) − (y,ϕ) = 0.
