Properties of discrete breathers in graphane from ab initio simulations

A density functional theory (DFT) study of the discrete breathers (DBs) in graphane (fully hydrogenated graphene) was performed. To the best of our knowledge, this is the first demonstration of the existence of DBs in a crystalline body from the first-principle simulations. It is found that the DB is a robust, highly localized vibrational mode with one hydrogen atom oscillating with a large amplitude along the direction normal to the graphane plane with all neighboring atoms having much smaller vibration amplitudes. DB frequency decreases with increase in its amplitude, and it can take any value within the phonon gap and can even enter the low-frequency phonon band. The concept of DB is then used to propose an explanation to the recent experimental results on the nontrivial kinetics of graphane dehydrogenation at elevated temperatures.Comment: 20.07.14 Submitted to PhysRev

Radio emission from satellite-Jupiter interactions (especially Ganymede)

Analyzing a database of 26 years of observations of Jupiter from the Nan\c{c}ay Decameter Array, we study the occurrence of Io-independent emissions as a function of the orbital phase of the other Galilean satellites and Amalthea. We identify unambiguously the emissions induced by Ganymede and characterize their intervals of occurrence in CML and Ganymede phase and longitude. We also find hints of emissions induced by Europa and, surprisingly, by Amalthea. The signature of Callisto-induced emissions is more tenuous.Comment: 14 pages, 7 figures, in "Planetary Radio Emissions VIII", G. Fischer, G. Mann, M. Panchenko and P. Zarka eds., Austrian Acad. Sci. Press, Vienna, in press, 201

Stability of Nonlinear Normal Modes in the FPU-β\beta Chain in the Thermodynamic Limit

All possible symmetry-determined nonlinear normal modes (also called by simple periodic orbits, one-mode solutions etc.) in both hard and soft Fermi-Pasta-Ulam-$\beta$ chains are discussed. A general method for studying their stability in the thermodynamic limit, as well as its application for each of the above nonlinear normal modes are presented

Jupiter radio emission induced by Ganymede and consequences for the radio detection of exoplanets

International audienceBy analysing a database of 26 yr of observations of Jupiter with the Nancay Decameter Array, we unambiguously identify the radio emissions caused by the Ganymede-Jupiter interaction. We study the energetics of these emissions via the distributions of their intensities, duration, and power, and compare them to the energetics of the Io-Jupiter radio emissions. This allows us to demonstrate that the average emitted radio power is proportional to the Poynting flux from the rotating Jupiter's magnetosphere intercepted by the obstacle. We then generalize this result to the radio-magnetic scaling law that appears to apply to all plasma interactions between a magnetized flow and an obstacle, magnetized or not. Extrapolating this scaling law to the parameter range corresponding to hot Jupiters, we predict large radio powers emitted by these objects, that should result in detectable radio flux with new-generation radiotelescopes. Comparing the distributions of the durations of Ganymede-Jupiter and Io-Jupiter emission events also suggests that while the latter results from quasi-permanent Alfven wave excitation by Io, the former likely results from sporadic reconnection between magnetic fields Ganymede and Jupiter, controlled by Jupiter's magnetic field geometry and modulated by its rotation