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Amber Stinson

Publications and source records attributed to Amber Stinson.

3 recordsLinked to original sources

Bayesian Inference of the Landau Parameter $G'_0$ from Joint Gamow-Teller Measurements

$G'_0$ is the leading-order Landau-Migdal parameter that characterizes the spin-isospin dependent nucleon-nucleon interaction. Consequently, the $G'_0$ is closely related to the Gamow-Teller resonance (GTR), the beta and double-beta decay rates of finite nuclei, the response of hot and dense nucleonic matter that modifies the neutrino-nucleon absorption rates in core-collapse supernovae (CCSNe) and binary neutron star (BNS) mergers, and finally the critical density for pion condensation in neutron stars. In this letter, for the first time, we report the $G'_0$ with quantified uncertainty in the framework of Bayesian inference, using a self-consistent standard Skyrme Random Phase Approximation (RPA) model and joint constraints from experimental GTR measurements on $^{208}\mathrm{Pb}$, $^{132}\mathrm{Sn}$, $^{90}\mathrm{Zr}$. Our extracted $G_0'$ at saturation density is $0.48\pm0.034$, which is close to the prediction of a few existing Skyrme models that consider spin-isospin observables but smaller than the traditional ones extracted from pion-exchange models. The reasons for this deviation, like the value of the nucleon effective mass $\frac{m^*}{m}$ and the density dependence of $G'_0$, are investigated. The density-dependent $G_0'$ values extracted in this work may guide the construction of new energy density functionals that aims to self-consistently describe the dense matter properties in the spin-isospin channel.

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Information content of the Gamow Teller Resonance: Bayesian inference with self-consistent Skyrme models

Many important charge-exchange weak processes, such as beta decays, double beta decays, and neutrino-nucleus and neutrino-nucleon reactions, are closely related to the spin- and isospin-dependent nuclear force, yet few of them can be precisely measured, or even observed, in terrestrial experiments. The Gamow-Teller resonance (GTR) in finite nuclei is one of the few experimental probes of this spin-isospin force. In a companion letter, we obtained the probability distribution of the Landau-Migdal parameter $G'_0$, which characterizes the main part of the spin-isospin force, from GTR measurements using Bayesian inference. In this follow-up work, we quantitatively study the correlations emerging from this Bayesian analysis. From the posterior, we identify two standard Skyrme parameterizations (nuSky*) that reproduce, in a unified manner, ground-state observables of finite nuclei, the salient features of the GTR, and the bulk properties of neutron-star matter. Since collective excitations in finite nuclei and in neutron-star matter are related, we use the Skyrme interactions sampled from the posterior to constrain the axial-current, charged-current neutrino-nucleon reaction rates in hot and dense compact-star matter, as the first astrophysical application of this study. The GTR-informed calculations substantially reduce the spread of the neutrino opacity; nevertheless, significant uncertainties remain due to the poorly constrained symmetry energy at sub-saturation densities. Constraining this quantity on top of a well-constrained spin-isospin interaction would pave the way towards a systematic determination of neutrino interactions in dense matter.

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Glassy quantum nuclear pasta in neutron star crusts

We investigate the nuclear pasta phases in neutron star crusts by conducting a large number of three-dimensional Hartree-Fock+BCS calculations at densities leading to the crust-core transition. We survey the shape parameter space of pasta at constant pressure. Spaghetti, waffles, lasagna, bi-continuous phases and cylindrical holes occupy local minima in the resulting Gibbs energy surfaces. The bi-continuous phase, in which both the neutron gas and nuclear matter extend continuously in all dimensions and therefore protons are delocalized, appears over a large range of depths. Our results support the idea that nuclear pasta is a glassy system. Multiple pasta configurations coexist in a given layer of the crust. At a characteristic temperature, of order $10^8$-$10^9$K, different phases become frozen into domains whose sizes we estimate to be 1-50 times the lattice spacing and over which the local density and electron fraction can vary. Above this temperature, there is very little long-range order and matter is an amorphous solid. Electron scattering off domain boundaries may contribute to the disorder resistivity of the pasta phases. Annealing of the domains may occur during cooling; repopulating of local minima during crustal heating might lead to temperature dependent transport properties in the deep layers of the crust. We identify 4 distinct regions: (1) nuclear pasta first appears as a local minima, but spherical nuclei are the ground state; (2) nuclear pasta become the absolute minimum, but spherical nuclei are still a local minimum (3) only nuclear pasta appears in local minima, and protons are still localized in at least one dimension (4) only pasta appears, and protons are delocalized. The whole pasta region can occupy up to 70% of the crust by mass and 40% by thickness, and the layer in which protons are delocalized could occupy 45% of the crust mass and 25% of its thickness.

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