Slow and fast dynamics in coupled systems: A time series analysis view

We study the dynamics of systems with different time scales, when access only to the slow variables is allowed. We use the concept of Finite Size Lyapunov Exponent (FSLE) and consider both the case when the equations of motion for the slow components are known, and the situation when a scalar time series of one of the slow variables has been measured. A discussion on the effects of parameterizing the fast dynamics is given. We show that, although the computation of the largest Lyapunov exponent can be practically infeasible in complex dynamical systems, the computation of the FSLE allows to extract information on the characteristic time and on the predictability of the large-scale, slow-time dynamics even with moderate statistics and unresolved small scales.Comment: 17 pages RevTeX, 6 PostScript figures, tarred, gzipped, uuencoded. Submitted to Physica

Generation of large-scale winds in horizontally anisotropic convection

We simulate three-dimensional, horizontally periodic Rayleigh-B\'enard convection between free-slip horizontal plates, rotating about a distant horizontal axis. When both the temperature difference between the plates and the rotation rate are sufficiently large, a strong horizontal wind is generated that is perpendicular to both the rotation vector and the gravity vector. The wind is turbulent, large-scale, and vertically sheared. Horizontal anisotropy, engendered here by rotation, appears necessary for such wind generation. Most of the kinetic energy of the flow resides in the wind, and the vertical turbulent heat flux is much lower on average than when there is no wind

MASS SEGREGATION IN DARK MATTER MODELS.

We use the moments of counts of neighbors as given by the Generalized Correlation Integrals, to study the clustering properties of Dark Matter Halos (DH) in Cold Dark Matter (CDM) and Cold+Hot Dark Matter (CHDM) models. We compare the results with those found in the CfA and SSRS galaxy catalogs. We show that if we apply the analysis in redshift space, both models reproduce equally well the observed clustering of galaxies. Mass segregation is also found in the models: more massive DHs are more clustered compared with less massive ones. In redshift space, this mass segregation is reduced by a factor 2-3 due to the peculiar velocities. Observational catalogs give an indication of luminosity and size segregation, which is consistent with the predictions of the models. Because the mass segregation is smaller in redshift space, it is suggestive that the real luminosity or size segregation of galaxies could be significantly larger than what it is found in redshift catalogs.Comment: 13 pages including 9 figures (220 KB) in uuencoded compressed Postscript format. To appear in The Astrophysical Journal, June 10. Latex file and figures available at ftp://astrohp.ft.uam.es/pub/preprints/masse

«Репетиции смерти» в стихотворениях “Блюз беженцев» У.Х. Одена и «Беженцы» Р. Джаррелла (к вопросу осмысления проблемы беженцев в американской поззии о второй мировой войне)

The article deals with the best American poems devoted to refugees of the world war II. The comparative analyses based on the thematic and stylistic similarity was carried out. Various forms of the main artistic device – repetition – were studied

Produttivita primaria dell' ecosistema marino, turbolenza oceanica e cicli biogeochimici globali

Il ciclo globale del carbonio e la concentrazione atmosferica di CO2 sono influenzati dai flussi biogeochimici fra oceano ed atmosfera. Questi flussi dipendono dal funzionamento dell’ecosistema marino; modifiche significative nella dinamica del plancton e nella produttività primaria possono avere rilevanti effetti sul clima. La dinamica del plancton, a sua volta, risente degli effetti di trasporto e rimescolamento indotti dalle strutture a mesoscala quali vortici e fronti, che per questo motivo sono uno degli attori sulla scena della dinamica del clim