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Nuclear Theory·nucl-th

Monday·February 19, 2018

6 papers—2 primary·4 cross-listed

All6Primary2Cross-lists4
  1. 03

    A MUSTA-FORCE algorithm for solving partial differential equations of relativistic hydrodynamics

    J. Porter-Sobieraj · M. Słodkowski · D. Kikoła · J. Sikorski · P. Aszklar

    Understanding event-by-event correlations and fluctuations is crucial for the comprehension of the dynamics of heavy ion collisions. Relativistic hydrodynamics is an elegant tool for modeling these phenomena; however, such simulations are time-consuming, and conventional CPU calculations are not suitable for event-by-event calculations. This work presents a feasibility study of a new hydrodynamic code that employs graphics processing units together with a general MUSTA-FORCE algorithm (Multi-Stage Riemann Algorithm - First Order Centered scheme) to deliver a high-performance yet universal tool for event-by-event hydrodynamic simulations. We also investigate the performance of selected slope limiters that reduce the amount of numeric oscillations and diffusion in the presence of strong discontinuities and shock waves. The numerical results are compared to the exact solutions to assess the code's accuracy.

    ↳ physics.comp-phnucl-thInt.J.Nonlin.Sci.Numer.Simul.(2017)·1 citation
  2. 04

    Impacts of nuclear-physics uncertainties in the s-process determined by Monte-Carlo variations

    N. Nishimura · G. Cescutti · R. Hirschi · T. Rauscher · J. den Hartogh · A. St. J. Murphy

    The s-process, a production mechanism based on slow-neutron capture during stellar evolution, is the origin of about half the elements heavier than iron. Abundance predictions for s-process nucleosynthesis depend strongly on the relevant neutron-capture and -decay rates, as well as on the details of the stellar model being considered. Here, we have used a Monte-Carlo approach to evaluate the nuclear uncertainty in s-process nucleosynthesis. We considered the helium burning of massive stars for the weak s-process and low-mass asymptotic-giant-branch stars for the main s-process. Our calculations include a realistic and general prescription for the temperature dependent uncertainty for the reaction cross sections. We find that the adopted uncertainty for () rates, tens of per cent on average, effects the production of s-process nuclei along the line of -stability, and that the uncertainties in -decay from excited state contributions, has the strongest impact on branching points.

    ↳ astro-ph.SRnucl-exnucl-thJAEA-Conf 2018-001·5 citations
  3. 05

    Sensitivity to neutron captures and beta-decays of the enhanced s-process in rotating massive stars at low metallicities

    N. Nishimura · R. Hirschi · T. Rauscher

    The s-process in massive stars, producing nuclei up to , has a different behaviour at low metallicity if stellar rotation is significant. This enhanced s-process is distinct from the s-process in massive stars around solar metallicity, and details of the nucleosynthesis are poorly known. We investigated nuclear physics uncertainties in the enhanced s-process in metal-poor stars within a Monte-Carlo framework. We applied temperature-dependent uncertainties of reaction rates, distinguishing contributions from the ground state and from excited states. We found that the final abundance of several isotopes shows uncertainties larger than a factor of 2, mostly due to the neutron capture uncertainties. A few nuclei around branching points are affected by uncertainties in the -decay.

    ↳ astro-ph.SRnucl-exnucl-thJ.Phys.Conf.Ser.(2018)·1 citation
  4. 06

    The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems

    Giancarlo Calvanese Strinati🇮🇹 · Pierbiagio Pieri🇮🇹 · Gerd Roepke🇩🇪 · Peter Schuck🇫🇷 · Michael Urban🇫🇷

    This report adresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. After an introduction to present the key concepts of the BCS-BEC crossover, this report discusses the mean-field treatment of the superfluid phase, both for homogeneous and inhomogeneous systems, as well as for symmetric (spin- or isospin-balanced) and asymmetric (spin- or isospin-imbalanced) matter. Pairing fluctuations in the normal phase are then considered, with their manifestations in thermodynamic and dynamic quantities. The last two Sections provide a more specialized discussion of the BCS-BEC crossover in ultra-cold Fermi gases and nuclear matter, respectively. The separate discussion in the two contexts aims at cross communicating to both communities topics and aspects which, albeit arising in one of the two fields, share a strong common interest.

    ↳ cond-mat.quant-gascond-mat.str-elcond-mat.supr-connucl-thPhys.Rept.(2018)·173 citations

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first authorsco-authorsvia INSPIRE