Cosmological interpretation of the color-magnitude diagrams of galaxy clusters

We investigate the color-magnitude diagram (CMD) of cluster galaxies in the hierarchical $\Lambda$-CDM cosmological scenario using both single stellar populations and simple galaxy models. First, we analyze the effect of bursts and mergers and companion chemical pollution and rejuvenation of the stellar content on the integrated light emitted by galaxies. The dispersion of the galaxy magnitudes and colors on the $M_V-(B-V)$ plane is mainly due to mixing of ages and metallicities of the stellar populations, with mergers weighting more than bursts of similar mass fractions. The analysis is made using the Monte-Carlo technique applied to ideal model galaxies reduced to single stellar populations with galaxy-size mass to evaluate mass, age and metallicity of each object. We show that separately determining the contributions by bursts and mergers leads to a better understanding of observed properties of CMD of cluster galaxies. Then we repeat the analysis using suitable chemo-photometric models of galaxies whose mass is derived from the cosmological predictions of the galaxy content of typical clusters. Using the halo mass function and the Monte-Carlo technique, we derive the formation redshift of each galaxy and its photometric history. These are used to simulate the CMD of the cluster galaxies. The main conclusion is that most massive galaxies have acquired the red color they show today in very early epochs and remained the same ever since. The simulations nicely reproduce the Red Sequence, the Green Valley and the Blue Cloud, the three main regions of the CMD in which galaxies crowd.Comment: Accepted for publication in Ap

What do we know about the proton spin structure?

A brief summary of the theoretical and experimental knowledge of the spin structure of the proton is presented. The helicity distributions of quark and gluons are discussed, together with their related sum rules. The transversity distribution is also introduced with possible strategies for its measurement. Novel spin dependent and \bfk_\perp unintegrated distribution and fragmentation functions are discussed, in connection with a new and rich phenomenology of transverse single spin asymmetries.Comment: 8 pages, 5 figures, talk delivered at GDH02, July 3-6 2002, Genova, Ital

IFLA Congress in Italy for the fourth time , Libraries create futures: building on cultural heritage : final programme, Milan, Italy, 23-27 August 2009

Welcome of the Chair of the Italian National Committee. IFLA Congress comes back to Italy for the fourth time: 1929, 1951, 1964, and now 2009. In June 1929, in the Marciana Library (Venice), Mr. Isak Collijn announced the name of the Library Federation, and the Italian librarian Vincenzo Fago read the Statute, dated "Florence, June 25, 1929": 1) The name of this organization shall be the International Federation of Library Associations. 2) The object of the Federation shall be to promote international library cooperation. One year after, in 1930, the Italian Library Association (AIB) was founded

Noncompensatory Consideration and Compensatory Choice : an Application to Stackelberg Competition

I would like to thank Ran Spiegler for his helpful suggestions. I am also grateful to Miguel Angel Ballester, Johannes Hoerner, Philippe Jehiel, Erika Magnago, Paola Manzini, Marco Mariotti, William Neilson, an anonymous referee, the editor Nicholas C. Yannelis, and the seminar audience at Aberdeen and UCL for their comments. Any error is my own responsibility.Peer reviewedPreprin