JOHANSEN , Anders

We clarify the status of log-periodicity associated with speculative bubbles preceding financial crashes. In particular, we address Feigenbaum's [2001] criticism and show how it can be rebuked. Feigenbaum's main result is as follows: ``the hypothesis that the log-periodic component is present in the data cannot be rejected at the 95% confidence...

International audience

International audience

We analyze the ion concentration of groundwater issuing from deep wells located near the epicenter of the recent earthquake of magnitude 6.9 near Kobe, Japan, on January 17, 1995. These concentrations are well fitted by log-periodic modulations around a leading power law. The exponent (real and imaginary parts) is very close to those already...

At least 30% of main sequence stars host planets with sizes of between 1 and 4 Earth radii and orbital periods of less than 100 days. We use N -body simulations including a model for gas-assisted pebble accretion and disk–planet tidal interaction to study the formation of super-Earth systems. We show that the integrated pebble mass reservoir...

Giant planets migrate though the protoplanetary disc as they grow. We investigate how the formation of planetary systems depends on the radial flux of pebbles through the protoplanetary disc and on the planet migration rate. Our N-body simulations confirm previous findings that Jupiter-like planets in orbits outside the water ice line originate...

Previous simulations of planet formation utilizing single bodies including pebble accretion and planet migration imply that giant planets found in orbits exterior to 1 AU originate from the outer regions of protoplanetary discs (30-40 AU). Here we generalize such models to include the mutual gravity between a high number of growing planetary...

At least 30% of the FGK-type stars host "hot Super-Earths" with sizes between 1 and 4 Earth radii and orbital periods of less than 100 days. Here we use N-body simulations that simultaneously model gas-assisted pebble accretion and disk-planet tidal interaction to study the formation of hot super-Earths systems. Our results show that the...

Super-Earths are found in tighter orbits than the Earth's around more than one third of main sequence stars. It has been proposed that super-Earths are scaled-up terrestrial planets that formed similarly, through mutual accretion of planetary embryos, but in discs much denser than the solar protoplanetary disc. We argue instead that terrestrial...

Exoplanet surveys have discovered that a large fraction of planetary systems (perhaps, a third around Sun-like stars) possess super-Earth planets on orbits tighter than Earth's. These super-Earths with masses between that of Earth and Neptune are not found in the Solar System, however it has been proposed that they formed in a similar way to...