45,909 research outputs found

    Stellar footprints of a variable G

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    Theories with varying gravitational constant GG have been studied since long time ago. Among them, the most promising candidates as alternatives of the standard General Relativity are known as scalar-tensor theories. They provide consistent descriptions of the observed universe and arise as the low energy limit of several pictures of unified interactions. Therefore, an increasing interest on the astrophysical consequences of such theories has been sparked over the last few years. In this essay we comment on two methodological approaches to study evolution of astrophysical objects within a varying-GG theory, and the particular results we have obtained for boson and white dwarf stars.Comment: This essay received Honorable Mention in the 1999 Essay Competition of the Gravity Research Foundatio

    A Daily Diary Investigation of Latino Ethnic Identity, Discrimination, and Depression

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    The objectives of the current study were to document the effects of discrimination on Latino mental health and to identify the circumstances by which ethnic identity serves a protective function. Instances of discrimination and depressive symptoms were measured every day for 13 days in a sample of Latino adults (N = 91). Multilevel random coefficient modeling showed a 1-day lagged effect in which increases in depression were observed the day following a discriminatory event. The findings also revealed differential effects of ethnic identity exploration and commitment. Whereas ethnic identity exploration was found to exacerbate the influence of daily discrimination on next-day depression, ethnic identity commitment operated as a stress buffer, influencing the intensity of and recovery from daily discrimination. The findings are discussed within a stress and coping perspective that identifies appropriate cultural resources for decreasing the psychological consequences associated with daily discrimination

    Modelling incomplete fusion dynamics of weakly-bound nuclei at near-barrier energies

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    The classical dynamical model for reactions induced by weakly-bound nuclei at near-barrier energies is developed further. It allows a quantitative study of the role and importance of incomplete fusion dynamics in asymptotic observables, such as the population of high-spin states in reaction products as well as the angular distribution of direct alpha-production. Model calculations indicate that incomplete fusion is an effective mechanism for populating high-spin states, and its contribution to the direct alpha production yield diminishes with decreasing energy towards the Coulomb barrier. It also becomes notably separated in angles from the contribution of no-capture breakup events. This should facilitate the experimental disentanglement of these competing reaction processes.Comment: 12 pages, 7 figures (for better resolution figures please contact the author), Accepted in Journal of Physics

    Quark matter equation of state and stellar properties

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    In this paper we study strange matter by investigating the stability window within the QMDD model at zero temperature and check that it can explain the very massive pulsar recently detected. We compare our results with the ones obtained from the MIT bag model and see that the QMDD model can explain larger masses, due to the stiffening of the equation of state
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