34 research outputs found
Magnetic susceptibility of insulators from first principles
We present an {\it ab initio} approach for the computation of the magnetic
susceptibility of insulators. The approach is applied to compute
in diamond and in solid neon using density functional theory in the local
density approximation, obtaining good agreement with experimental data. In
solid neon, we predict an observable dependence of upon pressure.Comment: Revtex, to appear in Physical Review Lette
Optical potentials for the rare-isotope beam era
We review recent progress and motivate the need for further developments in
nuclear optical potentials that are widely used in the theoretical analysis of
nucleon elastic scattering and reaction cross sections. In regions of the
nuclear chart away from stability, which represent a frontier in nuclear
science over the coming decade and which will be probed at new rare-isotope
beam facilities worldwide, there is a targeted need to quantify and reduce
theoretical reaction model uncertainties, especially with respect to nuclear
optical potentials. We first describe the primary physics motivations for an
improved description of nuclear reactions involving short-lived isotopes,
focusing on its benefits for fundamental science discoveries and applications
to medicine, energy, and security. We then outline the various methods in use
today to build optical potentials starting from phenomenological, microscopic,
and ab initio methods, highlighting in particular the strengths and weaknesses
of each approach. We then discuss publicly-available tools and resources
facilitating the propagation of recent progresses in the field to
practitioners. Finally, we provide a set of open challenges and recommendations
for the field to advance the fundamental science goals of nuclear reaction
studies in the rare-isotope beam era.Comment: This paper is the outcome of the Facility for Rare Isotope Beams
Theory Alliance (FRIB - TA) topical program "Optical Potentials in Nuclear
Physics" held in March 2022 at FRIB. Its content is non-exhaustive, was
chosen by the participants and reflects their efforts related to optical
potential
Analysis of corrections to the eikonal approximation
Various corrections to the eikonal approximations are studied for two- and
three-body nuclear collisions with the goal to extend the range of validity of
this approximation to beam energies of 10 MeV/nucleon. Wallace's correction
does not improve much the elastic-scattering cross sections obtained at the
usual eikonal approximation. On the contrary, a semiclassical approximation
that substitutes the impact parameter by a complex distance of closest approach
computed with the projectile-target optical potential efficiently corrects the
eikonal approximation. This opens the possibility to analyze data measured down
to 10 MeV/nucleon within eikonal-like reaction models.Comment: 10 pages, 8 figure
Ab initio investigations of nuclei: scattering, deformation in He, radiative capture of protons on Be and Li and the X17 boson
International audienceWe apply the No-Core Shell Model with Continuum (NCSMC) that is capable of describing both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. The NCSMC can predict structure and dynamics of light nuclei and, by comparing to available experimental data, test the quality of chiral nuclear forces. We discuss applications of NCSMC to the scattering and the structure of Be, the p+Be and p+Li radiative capture and the production of the hypothetical X17 boson claimed in ATOMKI experiments. The Be(p,)B reaction plays a role in Solar nucleosynthesis and Solar neutrino physics and has been subject of numerous experimental investigations. We also highlight our investigation of the neutron rich exotic He that has been recently studied experimentally at TRIUMF with an unexpected deformation reported