On the representation of the gravitational potential of several model bodiesVestnik St. Petersburg University, Mathematics - Tập 49 - Trang 290-298 - 2016
E. D. Kuznetsov, K. V. Kholshevnikov, V. Sh. Shaidulin
A Laplace series of spherical harmonics Y
n
(θ, λ) is the most common representation of the gravitational potential for a compact body T in outer space in spherical coordinates r, θ, λ. The Chebyshev norm estimate (the maximum modulus of the function on the sphere) is known for bodies of an irregular structure:〈Y
...... hiện toàn bộ
On one class of numerical methods for solving stiff systems of differential equationsVestnik St. Petersburg University, Mathematics - Tập 45 - Trang 1-6 - 2012
I. K. Daugavet
The paper is concerned with a modification of a Cowell-type method: at each step the solution is evaluated at several points and only some first of these values are retained. Stability of these methods is examined. In particular, among the methods of this group we single out one method that has the fourth order of accuracy and is stable for stiff systems with any choice of integration step.
On the frequency spectrum of free vibrations of membranes and plates in contact with a fluidVestnik St. Petersburg University, Mathematics - Tập 49 - Trang 68-76 - 2016
D. N. Ivanov, N. V. Naumova, V. S. Sabaneev, P. E. Tovstik, T. P. Tovstik
A parallelepiped-shaped container, which is completely filled with a perfect incompressible fluid, is considered. The container is covered with an elastic lid, which is modeled by a membrane or a constant-thickness plate. The other faces of the container are nondeformable. The frequency spectrum of small free vibrations of the lid has been obtained taking into account the apparent mass of the flui...... hiện toàn bộ
On the Density of Pre-Orbits under Linear Toral EndomorphismsVestnik St. Petersburg University, Mathematics - Tập 53 - Trang 243-247 - 2020
Saeed Azimi, Khosro Tajbakhsh
It is known that if each pre-orbit of a non-injective endomorphism is dense, the endomorphism is transitive (i.e., a dense orbit exists). However, it is still unknown whether the pre-orbits of an Anosov map are dense, and the conditions necessary for all pre-orbits to be dense are also unknown. Using the properties of integral lattices, we construct our proof by considering the pre-orbits of linea...... hiện toàn bộ
Stable equivalence classes of self-injective algebras of tree class D nVestnik St. Petersburg University, Mathematics - Tập 41 - Trang 9-14 - 2008
Yu. V. Volkov
A classification up to stable equivalence of representation-finite self-injective algebras with associated Dynkin diagram D
n
is suggested. In each stable equivalence class, a representative is chosen, and the representatives are partitioned into five families of algebras, which are described in terms of quivers with relations.
Stability of Periodic Points of Diffeomorphisms of Multidimensional SpaceVestnik St. Petersburg University, Mathematics - Tập 51 - Trang 204-212 - 2018
E. V. Vasil’eva
We study the diffeomorphism of a multidimensional space into itself with a hyperbolic fixed point at the origin and a nontransversal homoclinic point. From the works of Sh. Newhouse, B.F. Ivanov, L.P. Shilnikov, and other authors, it follows that there is a method of tangency for the stable and unstable manifold such that the neighborhood of a nontransversal homoclinic point can contain an infinit...... hiện toàn bộ
Global stability conditions of a system with hysteresis nonlinearityVestnik St. Petersburg University, Mathematics - Tập 50 - Trang 138-144 - 2017
V. A. Pliss, T. E. Zviagintceva
The paper discusses a two-dimensional automatic control system that contains a single hysteresis element of the general form. Systems of this type are mathematical models of real control systems and have been considered in many papers on this subject. In this paper, a system phase space, which is a manifold with a boundary, is constructed. The conditions under which the system is globally stable i...... hiện toàn bộ
#Analysis