Nuclear physics in core-collapse supernovae

Liebendörfer, M.; Fischer, Tobias; Fröhlich, C.; Hix, W. R.; Langanke, K.; Martı́nez-Pinedo, G.; Mezzacappa, Anthony; Scheidegger, Simon; Thielemann, Friedrich‐Karl; Whitehouse, Stuart C.

doi:10.1016/j.newar.2008.05.006

Cited by 6 publications

(46 citation statements)

References 39 publications

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“…8. The gradual increase of total strength with initial excitation corroborates the result for 28 Si (Fig. 3) and suggests it is a general feature of nuclei, at least in the sd shell.…”

Section: B 24 Mgsupporting

confidence: 85%

“…For the sake of connecting our 28 Si results with earlier work, we computed the GT strengths for 24 Mg. Frazier et al [58] examined total strength as a function of excitation and found results similar to ours, given in Fig. 8.…”

Section: B 24 Mgmentioning

confidence: 93%

“…The C i are dimensionless, and the other parameters are in units of MeV. 28 Si as a function of excitation energy. Each point corresponds to an individual state computed from the shell model, giving a GT sum rule for that state.…”

Section: A 28 Simentioning

confidence: 99%

“…To this end, we examined single-particle distribution as a function of nuclear excitation energy. Figure 7 shows the average singleparticle state occupations as functions of excitation energy for T = 0 states in 28 Si. The most salient features are that the 1d state occupations have a linear dependence on nuclear excitation with slopes of roughly 1 particle per 12 MeV (which is approximately the spin-orbit splitting energy + particle-hole repulsion energy in this subshell), while the 2s 1/2 occupation is independent of excitation; this is in contrast to FFNII [45], which assumed that the average occupations of all singleparticle states were independent of nuclear excitation energy.…”

Section: A 28 Simentioning

confidence: 99%

“…7 to be split proportionately between the valence protons and neutrons. In the case of 28 Si, then, the proton and neutron single-particle occupation numbers are each 1/2 the total occupation. This implies that the 1 particle per 12 MeV slope in Fig.…”

Section: A 28 Simentioning

confidence: 99%

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Modification of the Brink-Axel hypothesis for high-temperature nuclear weak interactions

2014

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We present shell-model calculations of electron capture strength distributions in A = 28 nuclei and computations of the corresponding capture rates in supernova core conditions. We find that in these nuclei the Brink-Axel hypothesis for the distribution of Gamow-Teller strength fails at low and moderate initial excitation energy but may be a valid tool at high excitation. The redistribution of GT strength at high initial excitation may affect capture rates during collapse. If these trends which we have found in lighter nuclei also apply for the heavier nuclei which provide the principal channels for neutronization during stellar collapse, then there could be two implications for supernova core electron capture physics. First, a modified Brink-Axel hypothesis could be a valid approximation for use in collapse codes. Second, the electron capture strength may be moved down significantly in transition energy, which would likely have the effect of increasing the overall electron capture rate during stellar collapse.

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“…8. The gradual increase of total strength with initial excitation corroborates the result for 28 Si (Fig. 3) and suggests it is a general feature of nuclei, at least in the sd shell.…”

Section: B 24 Mgsupporting

confidence: 85%

Section: B 24 Mgmentioning

confidence: 93%

Section: A 28 Simentioning

confidence: 99%

Section: A 28 Simentioning

confidence: 99%

Section: A 28 Simentioning

confidence: 99%

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Modification of the Brink-Axel hypothesis for high-temperature nuclear weak interactions

2014

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Modeling nuclear “pasta” and the transition to uniform nuclear matter with the 3D Skyrme-Hartree-Fock method at finite temperature: Core-collapse supernovae

2009

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The first results of a new three-dimensional, finite temperature Skyrme-Hartree-Fock+BCS study of the properties of inhomogeneous nuclear matter at densities and temperatures leading to the transition to uniform nuclear matter are presented. Calculations are carried out in a cubic box representing a unit cell of the locally periodic structure of the matter. A constraint is placed on the two independent components of the quadrupole moment of the neutron density in order to investigate the dependence of the total energy-density of matter on the geometry of the nuclear structure in the unit cell.This approach allows self-consistent modeling of effects such as (i) neutron drip, resulting in a neutron gas external to the nuclear structure, (ii) shell effects of bound and unbound nucleons, (iii) the variety of exotic nuclear shapes that emerge, collectively termed 'nuclear pasta' and (iv) the dissolution of these structures into uniform nuclear matter as density and/or temperature increase.In part I of this work the calculation of the properties of inhomogeneous nuclear matter in the core collapse of massive stars is reported. Emphasis is on exploring the effects of the numerical method on the results obtained; notably, the influence of the finite cell size on the nuclear shapes and energy-density obtained. Results for nuclear matter in beta-equilibrium in cold neutrons stars are subject of part II. The calculation of the band structure of unbound neutrons in neutron star matter, yielding thermal conductivity, specific heat and entrainment parameters, will be outlined in part III.Calculations are performed at baryon number densities of n b = 0.04 -0.12 fm −3 , a proton fraction of y p = 0.3 and temperatures in the range 0 -7.5 MeV. A wide variety of nuclear shapes are shown to emerge. It is suggested that thermodynamical properties change smoothly in the pasta regime up to the transition to uniform matter; at that transition, thermodynamic properties of the matter vary discontinuously, indicating a phase transition of first or second order. The calculations are carried out using the SkM * Skyrme parameterization; a comparison with calculations using Sly4 at n b = 0.08 fm −3 , T = 0 MeV is made.

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Neutrino-pair emission from hot nuclei during stellar collapse

2013

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We present shell-model calculations showing that residual interaction-induced configuration mixing enhances the rate of neutral current de-excitation of thermally excited nuclei into neutrinoantineutrino pairs. Though our calculations reinforce the conclusions of previous studies that this process is the dominant source of neutrino pairs near the onset of neutrino trapping during stellar collapse, our shell-model result has the effect of increasing the energy of these pairs, possibly altering their role in entropy transport in supernovae.

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Nuclear physics in core-collapse supernovae

Cited by 6 publications

References 39 publications

Modification of the Brink-Axel hypothesis for high-temperature nuclear weak interactions

Modification of the Brink-Axel hypothesis for high-temperature nuclear weak interactions

Modeling nuclear “pasta” and the transition to uniform nuclear matter with the 3D Skyrme-Hartree-Fock method at finite temperature: Core-collapse supernovae

Neutrino-pair emission from hot nuclei during stellar collapse

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