arXiv subjects
Publications and source records attributed to Stefan Rauch-Wojciechowski.
The dynamical equations for a gliding Lagrange top are not integrable. They have 5 dynamical variables and admit one integral of motion. We show that all solutions go to one of the two vertical spinning solutions and determine conditions of their stability. This means that solutions starting close to either of the spinning solutions go asymptotically to this solution.
The existing results about inversion of a tippe top (TT) establish stability of asymptotic solutions and prove inversion by using the LaSalle theorem. Dynamical behaviour of inverting solutions has only been explored numerically and with the use of certain perturbation techniques. The aim of this paper is to provide analytical arguments showing oscillatory behaviour of TT through the use of the main equation for the TT. The main equation describes time evolution of the inclination angle $θ(t)$ within an effective potential $V(\cosθ,D(t),λ)$ that is deforming during the inversion. We prove here that $V(\cosθ,D(t),λ)$ has only one minimum which (if Jellett's integral is above a threshold value $λ>λ_{\text{thres}}=\frac{\sqrt{mgR^3I_3α}(1+α)^2}{\sqrt{1+α-γ}}$ and $1-α^2<γ=\frac{I_1}{I_3}<1$ holds) moves during the inversion from a neighbourhood of $θ=0$ to a neighbourhood of $θ=π$. This allows us to conclude that $θ(t)$ is an oscillatory function. Estimates for a maximal value of the oscillation period of $θ(t)$ are given.
We study the relationship between numerical solutions for inverting Tippe Top and the structure of the dynamical equations. The numerical solutions confirm oscillatory behaviour of the inclination angle $θ(t)$ for the symmetry axis of the Tippe Top. They also reveal further fine features of the dynamics of inverting solutions defining the time of inversion. These features are partially understood on the basis of the underlying dynamical equations.
Equations of motion of an axially symmetric sphere rolling and sliding on a plane are usually taken as model of the tippe top. We study these equations in the nonsliding regime both in the vector notation and in the Euler angle variables when they admit three integrals of motion that are linear and quadratic in momenta. In the Euler angle variables $(θ,ϕ,ψ)$ these integrals give separation equations that have the same structure as the equations of the Lagrange top. It makes it possible to describe the whole space of solutions by representing them in the space of parameters $(D,λ,E)$ being constant values of the integrals of motion.
A conservative Newton system (d/dt)^2 q = -grad V(q) in R^n is called separable when the Hamilton--Jacobi equation for the natural Hamiltonian H = (1/2) p^2 + V(q) can be solved through separation of variables in some curvilinear coordinates. If these coordinates are orhogonal, the Newton system admits n first integrals, which all have separable Stackel form with quadratic dependence on p. We study here separability of the more general class of Newton systems (d/dt)^2 q = -cof G^(-1) grad W(q) that admit n quadratic first integrals. We prove that a related system with the same integrals can be transformed through a non-canonical transformation into a Stackel separable Hamiltonian system and solved by qudratures, providing a solution to the original system. The separation coordinates, which are defined as characteristic roots of a linear pencil (G - mu G~) of elliptic coordinates matrices, generalize the well known elliptic and parabolic coordinates. Examples of such new coordinates in two and three dimensions are given. These results extend, in a new direction, the classical separability theory for natural Hamiltonians developed in the works of Jacobi, Liouville, Stackel, Levi-Civita, Eisenhart, Benenti, Kalnins and Miller.
Systems of Newton equations of the form $\ddot{q}=-{1/2}A^{-1}(q)\nabla k$ with an integral of motion quadratic in velocities are studied. These equations generalize the potential case (when A=I, the identity matrix) and they admit a curious quasi-Lagrangian formulation which differs from the standard Lagrange equations by the plus sign between terms. A theory of such quasi-Lagrangian Newton (qLN) systems having two functionally independent integrals of motion is developed with focus on two-dimensional systems. Such systems admit a bi-Hamiltonian formulation and are proved to be completely integrable by embedding into five-dimensional integrable systems. They are characterized by a linear, second-order PDE which we call the fundamental equation. Fundamental equations are classified through linear pencils of matrices associated with qLN systems. The theory is illustrated by two classes of systems: separable potential systems and driven systems. New separation variables for driven systems are found. These variables are based on sets of non-confocal conics. An effective criterion for existence of a qLN formulation of a given system is formulated and applied to dynamical systems of the Henon-Heiles type.