The 0.03-10Mo mass function of young open clusters

We report the present day mass functions (PDMFs) of 3 young open clusters over a mass range from 30 Jupiter masses to 10~\msunn. The PDMFs of the 3 clusters are remarkably similar, suggesting little impact of specific conditions (stellar density, metallicity, early dynamical evolution) on the mass distribution. Functional forms are provided to allow quantitative comparison with MFs derived in other environments.Comment: 6 pages, to appear in "IMF@50", Corbelli, Palla, Zinnecker ed

SACY - a Search for Associations Containing Young stars

The scientific goal of the SACY (Search for Associations Containing Young-stars) was to identify possible associations of stars younger than the Pleiades Association among optical counterparts of the ROSAT X-ray bright sources. High-resolution spectra for possible optical counterparts later than G0 belonging to HIPPARCOS and/or TYCHO-2 catalogs were obtained in order to assess both the youth and the spatial motion of each target. More than 1000 ROSAT sources were observed, covering a large area in the Southern Hemisphere. The newly identified young stars present a patchy distribution in UVW and XYZ, revealing the existence of huge nearby young associations. Here we present the associations identified in this survey.Comment: 8 pages, 2 figures, to appear in the Proceedings of Open Issues in Local Formation and Early Stellar Evolution, Ouro Preto, Brazi

Legal determinants of external finance revisited : the inverse relationship between investor protection and societal well-being

This paper investigates relationships between corporate governance traditions and quality of life as measured by a number of widely reported indicators. It provides an empirical analysis of indicators of societal health in developed economies using a classification based on legal traditions. Arguably the most widely cited work in the corporate governance literature has been the collection of papers by La Porta et al. which has shown, inter alia, statistically significant relationships between legal traditions and various proxies for investor protection. We show statistically significant relationships between legal traditions and various proxies for societal health. Our comparative evidence suggests that the interests of investors may not be congruent with the interests of wider society, and that the criteria for judging the effectiveness of approaches to corporate governance should not be restricted to financial metrics

Coupling parameters and the form of the potential via Noether symmetry

We explore the conditions for the existence of Noether symmetries in the dynamics of FRW metric, non minimally coupled with a scalar field, in the most general situation, and with nonzero spatial curvature. When such symmetries are present we find general exact solution for the Einstein equations. We also show that non Noether symmetries can be found. Finally,we present an extension of the procedure to the Kantowski- Sachs metric which is particularly interesting in the case of degenerate Lagrangian.Comment: 13 pages, no figure

Gli uccelli delle isole circumsiciliane

Gli autori sintetizzano tutte le informazioni bibliografiche e inedite sulle specie che sino al 30 agosto 2015 sono state contattate almeno una volta nelle 14 isole circumsiciliane (Eolie, Ustica, Egadi, Pantelleria e Pelagie), confrontando alla fine la lista complessiva con quella delle isole Maltesi. In totale sono ad oggi note 434 specie (isole Maltesi incluse); molte di esse hanno mostrato nel corso dei secoli una notevole capacità di colonizzazione, fluttuando nel tempo o addirittura estinguendosi e ricolonizzando alcune isole. Questi piccoli territori in mezzo al mare rappresentano ottimi siti di controllo dell’andamento delle migrazioni nel corso dei decenni; alcune specie hanno chiaramente cambiato il loro status rispetto al passato, aumentando o diminuendo. Nel corso di circa 15 anni in alcune di queste isole (Ustica, Marettimo, Lampedusa e Linosa) sono stati condotti dei campi di inanellamento sia primaverili sia autunnali che hanno permesso di inanellare 102.208 uccelli, in gran parte Passeriformes; ciò ha consentito di raccogliere una notevole mole di dati sulle strategie migratorie, che vengono qui brevemente presentati. Le piccole isole sono davvero importanti per gli uccelli migratori transahariani, che devono sostare durante i loro lunghi viaggi per recuperare energie; la disponibilità di risorse sotto forma di frutti selvatici o di insetti (a seconda delle specie) consente a queste masse di migratori di continuare il loro viaggio. La conservazione degli uccelli è dettata dalla Direttiva Uccelli e l’istituzione delle Zone di Protezione Speciale ha proprio lo scopo di salvaguardare alcune specie in determinati territori. Questo è un impegno preso da parte di tutti i Paesi dell’Unione Europea, proprio perché le popolazioni di uccelli non conoscono confini amministrativi e la loro tutela va al di là delle competenze e degli interessi di un singolo Paese. Per quanto riguarda le specie nidificanti, è risultata un’elevata correlazione negativa (r=-0,746), altamente significativa (P=0,002) tra la capacità dispersiva media delle specie e la superficie in km2 delle isole. Le specie con minore capacità dispersiva hanno colonizzato le isole di maggiori dimensioni, ma non quelle più piccole; questo con molta probabilità dipende dalla eterogeneità ambientale, a sua volta legata alla dimensione delle isole ed alla loro posizione geografica. Nel caso delle isole circumsiciliane, sembra che non sia tanto la distanza dalla costa a determinare il numero di specie, quanto le condizioni ambientali e la posizione geografica; indubbiamente la posizione tirrenica delle isole settentrionali rappresenta un vantaggio per la presenza di habitat differenziati e la conseguente colonizzazione di specie ad essi legate, mentre la posizione meridionale, influenzata dall’aridità africana, riduce alcune possibilità colonizzatrici da parte di alcune specie di uccelli e rende altresì problematica la stessa esistenza di habitat diversificati. Il numero delle specie nidificanti in un’isola è variabile nel tempo, essendovi specie che vi nidificano in modo irregolare. La correlazione area/N° specie nelle isole circumsiciliane è pari a 0,58, ma se si esclude l’isola di Pantelleria, sale a 0,86; essa è pari a 0,92 per le sole isole settentrionali (Eolie, Ustica ed Egadi), mentre risulta 0,99 per le sole tre isole meridionali del Canale di Sicilia.Authors summarize all bibliographic and unpublished information on bird species that have been detected at least one time up to 30th August 2015 in the 14 circum-sicilian islands (Eolian, Ustica, Egadi, Pantelleria and Pelagian Is.). The Appendix 1 compares overall lists with that of the Maltese Is., also lying in the Sicilian waters. On the whole, 434 species are known till now (Maltese Is. included); many of them showed a high colonizing capacity along the centuries, fluctuating or even becoming extinct and re-colonising some islands. These small territories in the middle of the Mediterranean sea are very good check-control sites of long-term migration trend; compared to the past, some species changed their status, increasing or declining. Additionally, during the last 15 years in some of these islands (Ustica, Marettimo, Lampedusa and Linosa) bird ringing activity has been carried out, both in spring and in autumn; it allowed to ring 102,208 birds, mainly Passeriformes; this opportunity allowed to collect a remarkable amount of data on migration strategy, here presented. The small islands are very important stop-over sites for transsaharan migratory birds, that must rest during their long journey to recover fuel in the form of fat; the availability of natural resources, such as wild fruits or insects, allows these masses of migrant birds to continue their trip. The conservation of birds has been established by the Bird Directive and the institution of Zones of Special Protection has the aim to safeguard some species in some territories. This agreement was signed by all countries of the EU, because bird populations do not know administrative borders and their conservation lies beyond the interests and authorities of a single country. Concerning breeding birds, a high negative correlation (r=-0.746, P=0.002) has been found between the average dispersal power of species and the area in km2 of islands. Species with minor dispersal power colonized the biggest but not the smallest islands; this, very probably depended on habitat heterogeneity of islands, in turn linked to the size of them and to the geographical position, more than to the distance from the continental land. Tyrrhenian position of northern islands is certainly an advantage for the presence of diversified habitats and birds inhabiting them, whereas southern position of Pantelleria and Pelagian Is., as well as Maltese Is., affected by African dryness, decreases colonizing probabilities of some bird species and the same existence of diversified habitats. The number of breeding species in each island varied along the time and some species bred irregularly. The correlation area/No. species in the islands surrounding Sicily resulted to be 0.58, but if we exclude Pantelleria Is., it grows to 0.86; besides, it grows to 0.92 if we consider only northern islands (Eolian, Ustica and Egadi Is.), and to 0.99 if we consider only southern islands

Unified View of Scaling Laws for River Networks

Scaling laws that describe the structure of river networks are shown to follow from three simple assumptions. These assumptions are: (1) river networks are structurally self-similar, (2) single channels are self-affine, and (3) overland flow into channels occurs over a characteristic distance (drainage density is uniform). We obtain a complete set of scaling relations connecting the exponents of these scaling laws and find that only two of these exponents are independent. We further demonstrate that the two predominant descriptions of network structure (Tokunaga's law and Horton's laws) are equivalent in the case of landscapes with uniform drainage density. The results are tested with data from both real landscapes and a special class of random networks.Comment: 14 pages, 9 figures, 4 tables (converted to Revtex4, PRE ref added

A New Association of Post-T Tauri Stars Near The Sun

Observing ROSAT sources in 20 x 25 deg centered at the high latitude active star ER Eri, we found evidences for a new young nearby association (~30Myr at~60pc), the Horologium Association (HorA), formed by at least 10 probable and 6 possible members, some being Post-T Tauri stars. We examine several requirements that characterize a young association and they, together, create a strong evidence for the reality of the HorA. In fact, the Li line intensities are between those of the oldest classical T Tauri stars and the ones of the Local Association stars. The space velocities of the HorA relative to the Sun, U= -9.5+/-1.0, V = -20.9 +/- 1.1, W = -2.1 +/- 1.9, are not far from those of the Local Association. We suggest that some hotter and non-X-ray active stars, with similar space velocities, could be massive members of the HorA, among them, the nearby Be star Achernar. The maximum of the mass distribution function of the HorA is around 0.8 solar masses. At its distance, the projected size of the HorA, ~50 pc, would be larger than our surveyed area and many other members could have been missed. We also observed 3 control regions, two at northern and southern galactic latitudes and a third one in the known TW Hya Association (TWA), and the properties and distribution of their young stars strengthen the reality of the HorA. Contrary to the TWA, the only known binaries in the HorA are 2 very wide systems. The HorA is much more isolated from clouds and older than the TWA and could give some clues about the lifetime of the disks around T Tauri stars. Actually, none of the proposed members is an IRAS source indicating an advanced stage of the evolution of their accreting disks. ER Eri itself was found to be a RS CVn-like system.Comment: 25 pages, 5 eps figures, to appear in Astron.

Overcharging a Black Hole and Cosmic Censorship

We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordstrom black hole by throwing in a charged particle, as long as the backreaction effects may be considered negligible. Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the backreaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. We also briefly comment on a number of possible extensions.Comment: 26 pages, 3 figures, LaTe

Extended Inflation with a Curvature-Coupled Inflaton

We examine extended inflation models enhanced by the addition of a coupling between the inflaton field and the space-time curvature. We examine two types of model, where the underlying inflaton potential takes on second-order and first-order form respectively. One aim is to provide models which satisfy the solar system constraints on the Brans--Dicke parameter $\omega$. This constraint has proven very problematic in previous extended inflation models, and we find circumstances where it can be successfully evaded, though the constraint must be carefully assessed in our model and can be much stronger than the usual $\omega > 500$. In the simplest versions of the model, one may avoid the need to introduce a mass for the Brans--Dicke field in order to ensure that it takes on the correct value at the present epoch, as seems to be required in hyperextended inflation. We also briefly discuss aspects of the formation of topological defects in the inflaton field itself.Comment: 24 pages, LaTeX (no figures), to appear, Physical Review D, mishandling of the solar system constraint on extended gravity theories corrected, SUSSEX-AST 93/6-

Double Field Inflation

We present an inflationary universe model which utilizes two coupled real scalar fields. The inflation field $\phi$ experiences a first order phase transition and its potential dominates the energy density of the Universe during the inflationary epoch. This field $\phi$ is initially trapped in its metastable minimum and must tunnel through a potential barrier to reach the true vacuum. The second auxiliary field $\psi$ couples to the inflaton field and serves as a catalyst to provide an abrupt end to the inflationary epoch; i.e., the $\psi$ field produces a time-dependent nucleation rate for bubbles of true $\phi$ vacuum. In this model, we find that bubbles of true vacuum can indeed percolate and we argue that thermalization of the interiors can more easily take place. The required degree of flatness (i.e., the fine tuning) in the potential of the $\psi$ field is comparable to that of other models which invoke slowly rolling fields. Pseudo Nambu-Goldstone bosons may naturally provide the flat potential for the rolling field.Comment: 18 pages, 2 figures, This early paper is being placed on the archive to make it more easily accessible in light of recent interest in reviving tunneling inflationary models and as its results are used in an accompanying submissio