Volume 12, Number 5
Volume 12, Number 5, 2007
On the 150th anniversary of A.M.Lyapunov
Moeckel R.
Abstract
A chaotic invariant set is constructed for the planar threebody problem. The orbits in the invariant set exhibit many close approaches to triple collision and also excursions near infinity. The existence proof is based on finding appropriate "windows" in the phase space which are stretched across one another by flowdefined Poincaré maps.

Pesin Y.
Abstract
This is a surveytype article whose goal is to review some recent results on existence of hyperbolic dynamical systems with discrete time on compact smooth manifolds and on coexistence of hyperbolic and nonhyperbolic behavior. It also discusses two approaches to the study of genericity of systems with nonzero Lyapunov exponents.

Sinai Y. G.
Abstract
We consider the recurrent equation
$\Lambda_p = \frac{1}{p1} \sum\limits_{p_1=1}^{p1} f (\frac{p1}{p}) \Lambda_{p_1} · \Lambda_{pp_1}$ which depends on the initial condition $\Lambda_1=x$. Under some conditions on $f$ we show that there exists the value of x for which $\Lambda_p$ tends to a constant as p tends to infinity. 
Seipel J., Holmes P. J.
Abstract
The springloaded inverted pendulum (SLIP) model describes well the steadystate centerofmass motions of a diverse range of walking and running animals and robots. Here we ask whether the SLIP model can also explain the dynamic stability of these gaits, and we find that it cannot do so in many physicallyrelevant parameter ranges. We develop an actuated, lossy, clocktorqued SLIP, or CTSLIP, with more realistic hipmotor torque inputs, that can capture the robust stability properties observed in most animals and some legged robots. Variations of CTSLIP at a similar level of detail and complexity may also be appropriate for capturing the wholesystem centerofmass dynamics of locomotion of legged animals and robots varying widely in size and morphology. This paper contributes to a broader program to develop mathematical models, at varied levels of detail, that capture the dynamics of integrated organismal systems exhibiting integrated wholebody motion.

Butta P., Negrini P.
Abstract
We investigate the problem of the existence of trajectories asymptotic to elliptic equilibria of Hamiltonian systems in the presence of resonances.

Borisov A. V., Kozlov V. V., Mamaev I. S.
Abstract
We consider two problems from the rigid body dynamics and use new methods of stability and asymptotic behavior analysis for their solution. The first problem deals with motion of a rigid body in an unbounded volume of ideal fluid with zero vorticity. The second problem, having similar asymptotic behavior, is concerned with motion of a sleigh on an inclined plane. The equations of motion for the second problem are nonholonomic and exhibit some new features not typical for Hamiltonian systems. A comprehensive survey of references is given and new problems connected with falling motion of heavy bodies in fluid are proposed.

Steklov V. A.
Abstract
The speech presented by Academician V.A. Steklov of the Russian Academy of Sciences to the public session of the Academy on May 3rd 1919.
