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

像金这样的重元素是在哪里合成的，以及在哪里合成的，是宇宙中的主要谜团之一。这些元素的合成方式与大质量恒星的生死周期以及它们内部发生的核反应密切相关。大质量恒星超新星的爆炸性死亡可能导致黑洞和中子星，中子星是一种主要由中子组成的非常致密的物体。在超新星爆炸期间，绝大多数能量以中微子的形式释放，中微子是相互作用很弱的粒子，它们可以在没有扰动的情况下传播到地球，在那里它们可以被探测到。其中一些中微子与爆炸期间喷出的物质相互作用，成为产生新元素的一连串核反应的一部分。也有可能两颗中子星相遇。在合并过程中，又一次发射出大量的中微子，可以合成新的富含中子的元素。在这些天体物理场景中，发生了几个反应，包括中微子吸收、聚变、裂变、β衰变和光子吸收。所有这一切都发生在数百种不同的同位素上。中微子决定了抛射出的物质中有多少中子和质子。然而，由于质量物体产生的强大引力场，这些中微子可能会被偏转或吸收。另一方面，不同的反应取决于数百种同位素的物理性质，其中许多还没有测量到，可能无法进行实验。*拟议研究计划的主要目标是：1)准确描述超新星、中子星合并和黑洞吸积盘产生的中微子通量，考虑这些天体产生的强大引力场；2)考虑贝塔衰变、中微子吸收和贝塔延迟中子发射等反应对富中子元素合成的影响；3)确定中子星地壳的结构和输运性质。*我们预计，通过更好地描述中微子通量，我们将减少重元素丰度模拟中的巨大不确定性。我们还希望建议测量关键原子核的物理性质，这与重元素的合成最相关。这一成果将使科学界受益，因为可以将努力集中在这些关键目标上。最后，对中子星外壳的更好理解将使我们能够解释在吸积中子星中观察到的X射线爆炸后的冷却时间，并将有助于解释推测起源于这些天体物理地点的富质子核的合成。

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.