Consider analytical three-dimensional differential systems having a singular point at the origin such that its linear part is y∂x−λz∂z for some λ≠0. The restriction of to Center Manifold has nilpotent origin. We prove if restricted system analytic and center origin, with Andreev number 2, then admits formal inverse Jacobi multiplier. also centers systems, on manifolds, are limits Hopf-type cent...

It is proved that the solutions of Tikhonov systems, in addition to having property a limiting transition, are pseudoholomorphic under certain conditions additional A.N. Tikhonov’s theorem. At same time, number fast and slow variables can be anything. Both initial boundary value problems for systems this type considered.

Abstract Since in recent years most of the heavy tetraquarks are discovered by Belle, LHCb, BESIII, etc., it motivated us to study these exotic hadrons. To extent our knowledge about mass characteristics tetraquarks, we utilize spinless relativistic Bethe–Salpeter equation applying Cornell potential order calculate eigenvalue and tetraquarks. For this purpose, present an ansatz solution obtaine...