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Nuclear Theory·nucl-th

Monday·June 22, 2020

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    Probing the fission properties of neutron-rich actinides with the astrophysical process

    Nicole Vassh · Matthew R. Mumpower · Trevor M. Sprouse · Rebecca Surman · Ramona Vogt

    We review recent work examining the influence of fission in rapid neutron capture (-process) nucleosynthesis which can take place in astrophysical environments. We briefly discuss the impact of uncertain fission barriers and fission rates on the population of heavy actinide species. We demonstrate the influence of the fission fragment distributions for neutron-rich nuclei and discuss currently available treatments, including recent macroscopic-microscopic calculations. We conclude by comparing our nucleosynthesis results directly with stellar data for metal-poor stars rich in -process elements to consider whether fission plays a role in the so-called `universality' of -process abundances observed from star to star.

    nucl-thastro-ph.HEEPJ Web Conf.(2020)·3 citations
  2. 02

    Operator evolution from the similarity renormalization group and the Magnus expansion

    A.J. Tropiano🇺🇸 · S.K. Bogner🇺🇸 · R.J. Furnstahl🇺🇸

    The Magnus expansion is an efficient alternative to solving similarity renormalization group (SRG) flow equations with high-order, memory-intensive ordinary differential equation solvers. The numerical simplifications it offers for operator evolution are particularly valuable for in-medium SRG calculations, though challenges remain for difficult problems involving intruder states. Here we test the Magnus approach in an analogous but more accessible situation, which is the free-space SRG treatment of the spurious bound-states arising from a leading-order chiral effective field theory (EFT) potential with very high cutoffs. We show that the Magnus expansion passes these tests and then use the investigations as a springboard to address various aspects of operator evolution that have renewed relevance in the context of the scale and scheme dependence of nuclear processes. These aspects include SRG operator flow with band- versus block-diagonal generators, universality for chiral EFT Hamiltonians and associated operators with different regularization schemes, and the impact of factorization arising from scale separation. Implications for short-range correlations physics and the possibilities for reconciling high- and low-resolution treatments of nuclear structure and reactions are discussed.

    nucl-thhep-phnucl-exPRC(2020)·10 citations
  3. 03

    Alpha clustering and alpha-capture reaction rate from ab initio symmetry-adapted description of Ne

    A. C. Dreyfuss · K. D. Launey · J. E. Escher · G. H. Sargsyan · R. B. Baker · T. Dytrych · J. P. Draayer

    We introduce a new framework for studying clustering and for calculating alpha partial widths using ab initio wave functions. We demonstrate the formalism for Ne, by calculating the overlap between the O cluster configuration and states in Ne computed in the ab initio symmetry-adapted no-core shell model. We present spectroscopic amplitudes and spectroscopic factors, and compare those to no-core symplectic shell-model results in larger model spaces, to gain insight into the underlying physics that drives alpha-clustering. Specifically, we report on the alpha partial width of the lowest resonance in Ne, which is found to be in good agreement with experiment. We also present first no-core shell-model estimates for asymptotic normalization coefficients for the ground state, as well as for the first excited state in Ne that lies in a close proximity to the O threshold. This outcome highlights the importance of correlations for developing cluster structures and for describing alpha widths. The widths can then be used to calculate alpha-capture reaction rates for narrow resonances of interest to astrophysics. We explore the reaction rate for the alpha-capture reaction ONe at astrophysically relevant temperatures and determine its impact on simulated X-ray burst abundances.

    nucl-thastro-ph.SRPRC(2020)·47 citations

Affiliations

first authorsco-authorsvia INSPIRE