We study deformations of the standard embedding of the Lie algebra $Vect(S^1)$ of smooth vector fields on the circle, into the Lie algebra of functions on the cotangent bundle $T^*S^1$ (with respect to the Poisson bracket). We consider two analogous but different problems: (a) formal deformations of the standard embedding of $Vect(S^1)$ into the

We present the results of applying a new chemo-evolutionary stellar population model, developed in a previous paper, to new high-quality observational data of the nuclear regions of two representative elliptical galaxies and the bulge of the Sombrero galaxy. Here we fit in detail ~20 absorption lines and six optical and near-infrared colors

We present new BV photometry for 6564 stars in the field of the globular cluster NGC 6366, using a wide field CCD camera at the prime focus of the Isaac Newton Telescope (INT 2.5m). The mean internal accuracy of the present V magnitudes and (B-V) colours ranges from 0.005mag for the stars at the top of the Red Giant Branch to 0.07mag for the

We have obtained near-infrared observations of some of the faintest objects so far known towards the Pleiades young stellar cluster, with the purpose of investigating the sequence that connects cluster very low-mass stars with substellar objects. We find that infrared data combined with optical magnitudes are a useful tool to discriminate cluster

We present a new, fast and easy to use NLTE line formation code for ``unified atmospheres'' with spherical extension and stellar winds, developed for the (routine) spectroscopic analysis of luminous blue stars, covering the spectral range from ``A'' to ``O'' and including central stars of planetary nebulae. The major features of our code are: Data

We present the results of applying a new chemo-evolutionary stellar population model, developed in a previous paper, to new high-quality observational data of the nuclear regions of two representative elliptical galaxies and the bulge of the Sombrero galaxy. Here we fit in detail ~20 absorption lines and six optical and near-infrared colors