Thu·Oct 13, 2011Thursday·October 13, 2011

1. 01*

   Ab-initio approach to effective single-particle energies in doubly closed shell nuclei

   T. Duguet🇫🇷 · G. Hagen🇺🇸

   The present work discusses, from an ab-initio standpoint, the definition, the meaning, and the usefulness of effective single-particle energies (ESPEs) in doubly closed shell nuclei. We perform coupled-cluster calculations to quantify to what extent selected closed-shell nuclei in the oxygen and calcium isotopic chains can effectively be mapped onto an effective independent-particle picture. To do so, we revisit in detail the notion of ESPEs in the context of strongly correlated many-nucleon systems and illustrate the necessity to extract ESPEs through the diagonalization of the centroid {\it matrix}, as originally argued by Baranger. For the purpose of illustration, we analyse the impact of correlations on observable one-nucleon separation energies and non-observable ESPEs in selected closed-shell oxygen and calcium isotopes. We then state and illustrate the non-observability of ESPEs. Similarly to spectroscopic factors, ESPEs can indeed be modified by a redefinition of inaccessible quantities while leaving actual observables unchanged. This leads to the absolute necessity to employ consistent structure and reaction models based on the same nuclear Hamiltonian to extract the shell structure in a meaningful fashion from experimental data.

   ↳ nucl-thcond-mat.quant-gasnucl-exquant-phPRC(2012)·64 citations
2. 02*

   Physical Degrees of Freedom for Gauge Fields and the Issue of Spin

   T. Goldman🇺🇸

   The conflict between the physical degrees of freedom of gauge bosons and the Lorentz group irreps naturally used to describe their couplings to matter fields are illustrated and discussed, and applied to issues of linear and angular momentum.

   ↳ hep-phhep-exnucl-exnucl-thAIP Conf.Proc.(2011)·6 citations
3. 03*

   Nuclear physics in the cosmos

   C.A. Bertulani🇺🇸

   We observe photons and neutrinos from stars. Based on these observations, complemented by measurements of cosmic rays energies and composition, we have been able to constrain several models for the Big Bang and for stellar evolution. But that is not enough. We also need to help this effort with laboratory experiments. We are still far from being able to reproduce stellar environments in a terrestrial laboratory. But in many cases we can obtain accurate nuclear reaction rates needed for modeling primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are difficult to measure directly in the laboratory at the small astrophysical energies. In recent years indirect reaction methods have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this short review.

   ↳ nucl-thastro-ph.SRnucl-exPoS(2011)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.