http://dspace.nbuv.gov.ua:80/handle/123456789/169301 Tue, 14 Apr 2026 20:29:48 GMT 2026-04-14T20:29:48Z http://dspace.nbuv.gov.ua:80/bitstream/id/505933/ http://dspace.nbuv.gov.ua:80/handle/123456789/169301 http://dspace.nbuv.gov.ua:80/handle/123456789/169404 Abstracts Mon, 01 Jan 2018 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/169404 2018-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/169403 Про моногенні функції, визначені в різних комутативних алгебрах Шпаківський, В.С. Встановлено відповідність між моногенною функцією в довільній скінченновимірній комутативній асоціативній алгебрі і скінченним набором моногенних функцій в спеціальній комутативній асоціативній алгебрі. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/169403 2018-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/169402 On geodesic bifurcations of product spaces Ryparova, L.; Mikes, J.; Sabykanov, A. The bifurcation is described as a situation where there exist at least two different geodesics going through the given point in the given direction. In the previous works, the examples of local and closed bifurcations are constructed. This paper is devoted to the further study of these bifurcations. We construct an example of n-dimensional (pseudo-) Riemannian and Kahlerian spaces which are product ones that admit a local bifurcation of geodesics and also a closed geodesic. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/169402 2018-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/169401 Approximate controllability of the wave equation with mixed boundary conditions Pestov, L.; Strelnikov, D. We consider initial boundary-value problem for acoustic equation in the time space cylinder Ω×(0, 2T) with unknown variable speed of sound, zero initial data, and mixed boundary conditions. We assume that (Neumann) controls are located at some part Σ × [0, T], Σ ⊂ ∂Ω of the lateral surface of the cylinder Ω × (0, T). The domain of observation is Σ × [0, 2T], and the pressure on another part (∂Ω\Σ) × [0, 2T]) is assumed to be zero for any control. We prove the approximate boundary controllability for functions from the subspace V ⊂ H¹(Ω) whose traces have vanished on Σ provided that the observation time is 2T more than two acoustic radii of the domain Ω. We give an explicit procedure for solving Boundary Control Problem (BCP) for smooth harmonic functions from V (i.e., we are looking for a boundary control f which generates a wave uf such that uf (., T) approximates any prescribed harmonic function from V ). Moreover, using the Friedrichs–Poincar´e inequality, we obtain a conditional estimate for this BCP. Note that, for solving BCP for these harmonic functions, we do not need the knowledge of the speed of sound. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/169401 2018-01-01T00:00:00Z