We have studied the sensitivity of s-process nucleosynthesis in massive stars to ±2σ variations in the rates of the triple-α and C(α, γ)O reactions. We simulated the evolution of massive stars from H-burning through Fe-core collapse, followed by a supernova explosion. We found that: the production factors of s-process nuclides between Fe and Zr change strongly with changes in the He burning rea...

The success of primordial nucleosynthesis imposes stringent bounds on the abundance of gravitational relics. This is particularly true for gravitinos, which for models with gravitationally mediated supersymmetry breaking are expected to have a mass below the TeV scale and thus to decay only after nucleosynthesis has concluded. We discuss the nonthermal production of gravitinos in models with se...

We study three processes that shape the nuclear composition of the fireballs in gamma-ray bursts (GRBs): (1) neutronization in the central engine, (2) nucleosynthesis in the fireball as it expands and cools, and (3) spallation of nuclei in subsequent internal shocks. The fireballs are shown to have a neutron excess and a marginally successful nucleosynthesis. They are composed of free nucleons,...

A Higgs doublet which has a positive mass squared term and Yukawa couplings to the quarks will acquire a vacuum expectation value typically of the order of 10eV or less, as a result of chiral symmetry breaking. We consider nucleosynthesis constraints on models which use this fact as a basis for understanding very small Dirac neutrino masses without requiring very small Yukawa couplings. The sim...

Intense fluxes of neutrinos are emitted by the hot neutron star produced in a supernova. The average supernova neutrino energies satisfy a robust hierarchy 〈Eνe〉 < 〈Eν̄e〉 < 〈Eνμ(τ)〉 ≈ 〈Eν̄μ(τ)〉. The νe and ν̄e capture reactions on neutrons and protons, respectively, provide heating to drive a wind from the hot neutron star. The same reactions also determine the neutron-richness of the wind materia...

We study the r-process nucleosynthesis in neutrino-driven winds of gravitational core collapse SNeII. Appropriate physical conditions are found for successful r-process nucleosynthesis, which meet with several features of heavy elements discovered recently in metal-deficient halo stars. We find also several difficulties which are not explained in the present wind models. We discuss quests for n...

Of the elements strictly synthesized in stars, oxygen is by far the most abundantly produced. We review the nucleosynthesis and Galactic chemical evolution of this important element. We then review its isotopic composition in presolar grains recovered from primitive meteorites and from interplanetary dust particles. As we describe, knowledge of these isotopic compositions provide important cons...

We review the Cosmology and Physics underlying Primordial Nucleosynthesis and survey current observational data in order to compare the predictions of Big Bang Nucleosynthesis with the inferred primordial abundances. From this comparison we report on the status of the consistency of the standard hot big bang model, we constrain the universal density of baryons (nucleons), and we set limits to t...

It is well known that thermally pulsing Asymptotic Giant Branch stars with low mass play a relevant role in the chemical evolution. They have synthesized about 30% of the galactic carbon and provide an important contribution to the nucleosynthesis of heavy elements (A>80). The relevant nucleosynthesis site is the He-rich intermediate zone (less than 10 M⊙), where α(2α, γ) C reactions and slow n...

Half of the heavy elements including all actinides are produced in r-process nucleosynthesis, whose sites and history remain a mystery. If continuously produced, the Interstellar Medium is expected to build-up a quasi-steady state of abundances of short-lived nuclides (with half-lives ≤100 My), including actinides produced in r-process nucleosynthesis. Their existence in today's interstellar me...