Bifurcation cascades and self-similarity of periodic orbits with analytical scaling constants in Henon-Heiles type potentials

We investigate the isochronous bifurcations of the straight-line librating orbit in the Henon-Heiles and related potentials. With increasing scaled energy e, they form a cascade of pitchfork bifurcations that cumulate at the critical saddle-point energy e=1. The stable and unstable orbits created at these bifurcations appear in two sequences whose self-similar properties possess an analytical scaling behavior. Different from the standard Feigenbaum scenario in area preserving two-dimensional maps, here the scaling constants \alpha and \beta corresponding to the two spatial directions are identical and equal to the root of the scaling constant \delta that describes the geometric progression of bifurcation energies e_n in the limit n --> infinity. The value of \delta is given analytically in terms of the potential parameters.Comment: 20 pages, 10 figures, LaTeX. Contribution to Festschrift "To Martin C. Gutzwiller on His Seventy-Fifth Birthday", eds. A. Inomata et al., final revised version (updated references, note added in proof

Semiclassical description of shell effects in finite fermion systems

Since its first appearance in 1971, Gutzwiller's trace formula has been extended to systems with continuous symmetries, in which not all periodic orbits are isolated. In order to avoid the divergences occurring in connection with symmetry breaking and orbit bifurcations (characteristic of systems with mixed classical dynamics), special uniform approximations have been developed. We first summarize some of the recent developments in this direction. Then we present applications of the extended trace formulae to describe prominent gross-shell effects of various finite fermion systems (atomic nuclei, metal clusters, and a mesoscopic device) in terms of the leading periodic orbits of their suitably modeled classical mean-field Hamiltonians.Comment: LaTeX, 12 pages, 9 figures; invited contribution to Symposium "30 Jahre Gutzwiller Spurformel" at DPG spring meeting, Hamburg, March 28, 2001. To appear in Advances in Solid State Physic

Analyzing shell structure from Babylonian and modern times

We investigate ``shell structure'' from Babylonian times: periodicities and beats in computer-simulated lunar data corresponding to those observed by Babylonian scribes some 2500 years ago. We discuss the mathematical similarity between the Babylonians' recently reconstructed method of determining one of the periods of the moon with modern Fourier analysis and the interpretation of shell structure in finite fermion systems (nuclei, metal clusters, quantum dots) in terms of classical closed or periodic orbits.Comment: LaTeX2e, 13pp, 8 figs; contribution to 10th Nuclear Physics Workshop "Marie and Pierre Curie", 24 - 28 Sept. 2003, Kazimierz Dolny (Poland); final version accepted for J. Mod. Phys.

Normal forms and uniform approximations for bridge orbit bifurcations

We discuss various bifurcation problems in which two isolated periodic orbits exchange periodic ``bridge'' orbit(s) between two successive bifurcations. We propose normal forms which locally describe the corresponding fixed point scenarios on the Poincar\'e surface of section. Uniform approximations for the density of states for an integrable Hamiltonian system with two degrees of freedom are derived and successfully reproduce the numerical quantum-mechanical results.Comment: 25 pages, 18 figures, version published in Journal of Physics A: Mathematical and Theoretica