Abstract: Cosmic microwave background Stage-IV experiments and thirty-meter-class telescopes will come on line in the next decade. The convolution of these data sets will provide on order 1% precision for observables related to neutrino cosmology. Beyond Standard Model (BSM) physics could manifest itself in slight deviations from the standard predictions of quantities such as the neutrino energy density and the primordial abundances from Big Bang Nucleosynthesis (BBN). In this talk, I will argue for the need for precise and accurate numerical calculations of BBN. I will first show the detailed evolution of the neutrino spectra as they go out of equilibrium with the plasma. The spectra are important in changing the ratio of neutrons to protons. I will show how sensitive the primordial mass fraction of helium is to the weak interaction rates which evolve the neutron-to-proton ratio. Finally, I will present an example of how BSM physics can affect BBN by instituting an asymmetry between neutrinos and antineutrinos, commonly characterized by a lepton number.
Abstract: High-resolution spectrographic observations, combined with laboratory atomic physics data, have led to increasingly precise abundance determinations in stars. We have focused on elemental abundances in halo stars. These stars, among the oldest in our Galaxy, were seeded or \'polluted\' by the first generation of stars. We have extensively observed the n(eutron)-capture elements (synthesized in the slow or rapid process) and have recently initiated new studies of the iron-peak elements in the halo stars. To an observational limit, all of the halo stars show some evidence of n-capture elements. However, the r(apid)-process pattern varies (per star) with a complete r-process in some cases like CS 22892-052and only a weak or partial r-process pattern in other cases like HD 122563.Further, we see evidence of extensive n-capture elements in some stars in nearby dwarf galaxies. We find that several of the iron peak elements (Ti, V, Sc and Cr) show correlations. The observed elemental abundance ratios of these iron-peak elements can then be employed to explore the properties of explosive nucleosynthesis in, and to constrain models of, core-collapse supernovae.
Abstract: In nuclear astro-physics, the quantum simulation of large inhomogeneous dense systems as present in the crusts of neutron stars presents big challenges. The feasible number of particles in a simulation box with periodic boundary conditions is strongly limited due to the immense computational cost of the quantum methods. In this talk, we describe the techniques used to parallelize a state of the art density functional theory code that operates on an equidistant grid, and optimize its performance on distributed memory architectures. We also describe techniques to accelerate the compute-intensive matrix calculation part in this formalism. Presented techniques allow us to achieve good scaling and high performance on a large number of cores, as demonstrated through detailed performance analysis on Edison, a Cray XC30 supercomputer. Furthermore we show first applications simulating so called pasta phases with up to 6000 particles which was not possible without a highly parallelized code.
Abstract: Why not explore a career in the federal government? Most nuclear physicists are well aware of job opportunities in academia and national laboratories. But most do not consider a job in the federal government. Dr. Gillo will share her experiences as a member of the federal workforce, helping to manage the Nationâs Nuclear Physics Program. She will describe some of the challenges and excitements of being a federal employee, and describe how federal workers can make a contribution to nuclear physics.
Abstract: In my career as a historian, I wrote about one particularly sensitive subject: the choice of Weston, Illinois as the site for what came to be called Fermilab. This was a surprising and dismaying decision for many physicists, particularly those at the Lawrence Berkeley National Laboratory. After all, following in the tradition of Ernest Lawrence, managers and a world-class group of accelerator builders obtained initial funding and created the first design for the facility. To add further insult and injury, the loss of this particle physics laboratory signaled the end of the era when Berkeley housed the worldâs largest, most prestigious accelerators. When recently contemplating untold stories I would like to tell before retirement, I realized I am bothered by bits and pieces left out of my previously published work on the Fermilab decision, in particular what I discovered in my interactions with two key participants in that saga, Glenn Seaborg, then chairman of the Atomic Energy Commission, and Edwin McMillan, then director of Berkeley Lab. It is not that this missing information changes my published assessment or conclusions, which were shaped by dozens of interviews and a mountain of documents. Instead, I present this âin between the linesâ story of my experiences with Seaborg and McMillan to show case the job of a laboratory historian. In particular I want to share the scholarly as well as human joys and dilemmas encountered when doing this job, including the difficulty of dealing with and sorting through the emotions that arise when gathering information from history makers and the discomfort that comes with telling a story people donât want to hear. I also hope this account provides further insight into important history makers and the nuances of history-making.