Weak interactions, equations of state, and the synthesis of the elements

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How much and where heavy elements like Gold are synthesized is one of the major mysteries in the Universe. How these elements are synthesized is closely linked to the life and death cycle of massive stars as well as the nuclear reactions occurring in their interior.******The explosive death of a massive star, known as a Supernova, could have as an outcome a black hole with some matter accreting onto it, or a neutron star, a very compact object made mainly of neutrons. During a supernova explosion the vast majority of energy is released as neutrinos, weakly interacting particles, which can travel without perturbations and reach Earth where they can be detected. Some of these neutrinos interact with matter that has been ejected during the explosion and become part of a chain of nuclear reactions that produce new elements. It is also possible that two neutron stars encounter each other. During the merger, again huge numbers of neutrinos are emitted and new neutron-rich elements can be synthesized.******There are several reactions taking place in these astrophysical scenarios, including neutrino absorption, fusion, fission, beta decay, and photon absorption. All of this occurring on hundreds of different isotopes. Neutrinos determine how many neutrons vs protons are in the ejected material. However, due to the strong gravitational field caused by the massive object, these neutrinos could be deflected or absorbed. On the other hand, the different reactions depend on the physical properties of those hundreds of isotopes, many of them not yet measured and perhaps out of experimental reach. ******The main goals of the proposed research program are: 1) to accurately describe the neutrino fluxes emerging from Supernovae, neutron star mergers, and black hole accretion disks taking into account the strong gravitational field that these objects generate, 2) to account for the influence that reactions such as beta decay, neutrino absorption and beta delayed neutron emission have on the synthesis of neutron-rich elements, and 3) to determine the structure and transport properties of the neutron star crust.******We expect that with a better description of the neutrino fluxes we will reduce the large uncertainties in the modelling of the heavy elements abundances. We also expect to suggest measurements of the physical properties of key nuclei, which are the most relevant for the synthesis of heavy elements. This outcome will benefit the scientific community as efforts can be focus on these key targets. Finally, a better understanding of the neutron star crust will allow us to interpret the observed cooling times after x-ray explosions in accreting neutron stars, and will shed light on the synthesis of proton rich nuclei speculated to have their origin in these astrophysical sites.