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Computational Nuclear Astrophysics at the Exascale

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Title: Computational Nuclear Astrophysics at the Exascale


1
Computational Nuclear Astrophysicsat the Exascale
  • Stony Brook Nuclear Astrophysics
  • Alan Calder
  • Jim Lattimer
  • Eric Myra
  • Doug Swesty
  • Mike Zingale

2
  • Nuclear Astrophysics as an e.g.
  • Exascale computing will allow unprecedented,
    high-resolution, multidimensional, multiphysics
    end-to-end simulations that address the
    large-scale science challenges of E3SGS.
  • A Cosmic Simulator would need as input a
    detailed understanding of presently unsolved
    problems. Requires exascale computing with
    complementary algorithm development and the
    associated microphysical theory.
  • Nuclear Astrophysics has demonstrated itself as a
    field embracing computational science and
    large-scale computing. Significant progress has
    been made in the last 10 years with extant
    computational resources taking simulations to
    unprecedented levels and in developing
    computational technology.
  • We argue that computational astrophysics furthers
    the goals of E3SGS by
  • addressing the requisite problems (Type Ia
    Supernovae as standard candles)
  • developing parallel technologies for large-scale
    multiphysics simulations (see Flash Code and
    other publicly available technologies)
  • addressing the basic physics necessary for
    predictive science (VV)
  • Exascale computing will allow addressing a
    variety of cosmic problems including
  • Type Ia Supernovae and other thermonuclear flash
    problems
  • Core Collapse Supernove
  • Binary compact object evolution
  • Fundamentals of astrophysical objects
  • Predictions of neutrino and gravitational
    radiation signals

3
  • Why nuclear astro?
  • Reactive, multi-physics problems.
  • Consider morning talk- radiation transport,
    hydrodynamics, .

4
  • Core Collapse Supernovae Hypernovae/GRBs
  • Exascale computing would allow high-resolution
    3-D Radiation-magnetohydrodynamic models with
    full Boltzmann neutrino transport
  • Multiple timescales require use of implicit
    methods
  • Neutrino radiation cooling timescale gtgt
    hydrodynamic
  • and energy/lepton exchange timescales
  • Exascale computing gives us the resolution we
    need in 3-D
  • A (256 zone) x (256 zone) x (20 Energy group) 2-D
  • diffusion model is tractable on
    Seaborg _at_ 9.1 Tflops
  • A (256 zone) x (256 zone) x (256 zone) x
  • (200 group) x (100 direction) 3-D
    Boltzmann RMHD
  • model is tractable _at_ 1 Eflops
  • Such energy/directional resolution would allow us
    to resolve phenomena
  • such as nuclear recoil during neutrino scattering
    for the first time

5
  • Type Ia SN
  • Evolution to Ignition in Type Ias
  • True scale of convective evolution is centuries
  • Currently can evolve for hours before ignition
  • Exascale plus algorithm advances would allow
    evolution for
    months prior to convection
  • Physical Re 1014
  • Currently can model Re 104
  • Increases in resolution would allow us to
    determine of there is a Re dependence of the
    convective flow
  • Algorithmic advances needed fast elliptic solves
    on exascale architectures
  • Exascale would also allow
  • Larger nuclide networks
  • Full 3-D rad-transfer during expansion phase
    (ties models to Ia observables cosmology)
  • Could also address WD-WD mergers as an alternate
    scenario for Type Ias

6
  • X-ray bursts Novae
  • Share many physical, computational, algorithmic
    concerns with Type Ias
  • The principal modeling challenge is the poorly
    understood period of convection up to ignition of
    the burning front.
  • Exascale capabilities could allow us to
    understand
  • Nucleosynthesis of rp-process elements (XRB)
  • Paired with observations could give radius/mass
    relationship for neutron stars (XRB)
  • Galactic chemical evolution (Novae)

7
  • Binary NS-NS Mergers
  • Exascale computing would allow
  • 3-D GR post-Newtonian models with
  • Prediction of gravitational wave signals
  • Could allow gravitational astronomy of neutron
    star structure, i.e. determination of mass-radius
    relationship and hence constraints on the EOS of
    dense matter
  • Prediction of nucleosynthetic yields
  • full nuclide networks (could make detailed
    predictions of r-process nucleosynthesis to
    compare with observations)
  • Inclusion of full neutrino transport (alters
    temperature structure of neutron stars prior to
    and during merger)
  • Inclusion of magnetic fields
  • Allows modeling of possible short GRB mechanism
  • Evolution for much longer timescales
  • Many (100s-1000s) orbits prior to coalescence
  • Would allow calculation of gravitational wave
    signal during chirp phase

8
  • Equation of State of Hot, Dense Matter
  • Neutron Star Structure
  • Exascale computing allows
  • 3-D GR hydro models of neutron star seismology
  • Including MHD effects superfluidity in crust
  • Could predict mode-dependence on mass and radius
  • Can be compared with observed oscillations of
    soft-gamma repeaters (SGRs)
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