Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session L12: Dense Matter in Nuclear AstrophysicsRecordings Available
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Sponsoring Units: DNP Chair: Sanjana Curtis, University of Amsterdam Room: Shubert |
Sunday, April 10, 2022 3:45PM - 3:57PM |
L12.00001: Effect of the Nuclear Equation of State on Relativistic-Turbulence Induced Core-Collapse Supernovae Luca Boccioli, Grant J Mathews, Evan P O'Connor, In-Saeng J Suh The nuclear equation of state is an important component in the evolution of core-collapse supernovae. In this talk, I will present a survey of various Equations of State (EoS) in the literature and analyze their effect on spherical core-collapse models in which the effect of three-dimensional turbulence is introduced using a general relativistic version of the Mixing-Length model STIR (Couch et al. 2020). The explosion is quite EoS-dependent and it best correlates with the early-time entropy per baryon at the center of the Proto-Neutron Star (PNS). This is true across all progenitors that develop an iron core. Equations of state that produce larger central entropies result in stronger explosions. In addition to that, they are also correlated with more vigorous PNS convection, with wider convective layers in models exhibiting stronger explosions. |
Sunday, April 10, 2022 3:57PM - 4:09PM |
L12.00002: Response function for hot and dense nuclear matter from chiral effective field theory Eunkyoung Shin, Jeremy W Holt, Ermal Rrapaj, Sanjay K Reddy Core-collapse supernovae dynamics are still only partially understood. The limitations are: The multi-dimensional simulations of core-collapse supernovae do not produce explosions properly under the condition we expect. There are still big uncertainties in the equations of state and neutrino scattering and reaction rates. Therefore, it is still worth it to devote ourselves. We have studied response function up to 1st order perturbation of mean-field correction and vertex correction. The nuclear potential is obtained from chiral effective theory. We verified the result by comparing it with the former works of others, such as static response function and dynamic structure functions. We also discuss the ratio of neutrino scattering, which is meaningful in physics. |
Sunday, April 10, 2022 4:09PM - 4:21PM |
L12.00003: Constructing an Equation of State from Pure Neutron Matter Calculations Liam Brodie, Alexander Haber, Mark Alford, Ingo Tews The equation of state (EoS) for dense, beta-equilibrated nuclear matter is a fundamental ingredient for simulations of binary neutron star mergers, calculation of cooling curves, and other transport properties. We construct a new EoS using a relativistic-mean-field theory (RMF). Typically, the couplings in an RMF are fit to isospin-symmetric nuclear matter data, but the matter in neutron stars is much closer in composition to pure neutron matter. In this work, along with reproducing isospin-symmetric nuclear matter data, we also fit our RMF to pure neutron matter calculations from chiral effective field theory. These calculations are needed because it is not possible to perform experiments on pure neutron matter on Earth. Our EoS agrees with current mass and radius measurements from NICER and LIGO. |
Sunday, April 10, 2022 4:21PM - 4:33PM |
L12.00004: Speed of Sound for Hadronic and Quark Phases in a Magentic Field Aric A Hackebill, Efrain J Ferrer It is well known that for a fermion system with an isotropic equation of state (EOS), the stiffness of the EOS and the square of the speed of sound (SOS2) are equivalent. However, in the presence of a magnetic field the EOS becomes anisotropic with two different pressures arising, one directed parallel to the field direction and one perpendicular to it, which in principle may generate an anisotropy in the SOS. We determine the sense in which the stiffness of the parallel and perpendicular EOS may be interpreted as SOS and investigate the degree to which the magnetic field induced anisotropy affects the SOS of hadrons and quarks respectively. We find that for the systems considered, the affects of the magnetic field on the SOS anisotropy are mild up to 1018G. Links to neutron star physics are discussed throughout. |
Sunday, April 10, 2022 4:33PM - 4:45PM |
L12.00005: The Effect of Charge, Isospin, and Strangeness in the QCD Phase Diagram Critical End Point krishna P aryal, Veronica Dexheimer In this work, we discuss the deconfinement phase transition to quark matter in hot/dense matter. We examine the effect that different charge fractions, isospin fractions, net strangeness, and chemical equilibrium with respect to leptons have on the position of the coexistence line between different phases. In particular, we investigate how different sets of conditions that describe matter in neutron stars and their mergers, or matter created in heavy-ion collisions affect the position of the critical endpoint, namely where the first-order phase transition becomes a crossover. We also present an introduction to the topic of critical points, including a review of recent advances concerning QCD critical points. |
Sunday, April 10, 2022 4:45PM - 4:57PM |
L12.00006: Neutron Tunneling: A New Mechanism to Power Explosive Phenomena in Neutron Stars, Magnetars, and Neutron Star Mergers Carlos A Bertulani Neutron tunneling between neutron-rich nuclei in inhomogeneous dense matter encountered in neutron star crusts can release enormous energy on a short timescale to power explosive phenomena in neutron stars. In this work, we clarify aspects of this process that can occur in the outer regions of neutron stars when oscillations or cataclysmic events increase the ambient density. We use a time-dependent Hartree–Fock–Bogoliubov formalism to determine the rate of neutron diffusion and find that large amounts of energy can be released rapidly. The roles of nuclear binding, two-body interaction, and pairing in neutron diffusion times are investigated. We consider a one- dimensional quantum diffusion model and extend our analysis to study the impact of diffusion in three dimensions. We find that these novel neutron transfer reactions can generate energy huge amounts of energy under suitable conditions and assumptions. |
Sunday, April 10, 2022 4:57PM - 5:09PM |
L12.00007: Ejecta Composition Effects on Kilonova Parameter Inference Marko Ristic, Erika M Holmbeck, Ryan Wollaeger, Oleg Korobkin, Richard W O'Shaughnessy, Eve Chase, Chris Fryer, Chris J Fontes Kilonovae, one source of electromagnetic emission associated with neutron star mergers, are powered by the decay of radioactive isotopes in the neutron-rich merger ejecta. Variations in the elemental composition of the merger ejecta will affect the electromagnetic emission of a given kilonova and thus influence the model parameters inferred from such an event. In this work, we present an analysis comparing the mass-weighted elemental compositions of our radiative transfer simulations to the mass fractions of elements in the Sun. We explore how the overall abundance depends on the mass ejected through wind and dynamical mechanisms and identify those ejecta masses which best reproduce Solar abundances. We report the extent to which our parameter inference results depend on our assumed composition for the dynamical and wind ejecta and examine how the new results compare to previous work. |
Sunday, April 10, 2022 5:09PM - 5:21PM |
L12.00008: Using cosmic-ray positron and electron observations to probe the averaged properties of Milky Way pulsars and their time-evolution Ilias Cholis, Iason Krommydas Pulsars have long been studied in the electromagnetic spectrum. Their environments are rich in high-energy cosmic-ray electrons and positrons likely enriching the interstellar medium with such particles. In this work we use recent cosmic-ray observations from the AMS-02, CALET andDAMPE collaborations to study the averaged properties of the local Milky Way pulsar population. We perform simulations of the local Milky Way pulsar population, for interstellar medium assump- tions in agreement with a range of cosmic-ray nuclei measurements. Each such simulation contains $10^{4}$ pulsars of unique age, location, initial spin-down power and cosmic-ray electron/positron spectra. We produce more than $7 × 10^{3}$ such Milky Way pulsar simulations. We account for and study i) the pulsars' birth rates and the stochastic nature of their birth, ii) their initial spin-down power distribution, iii) their time evolution in terms of their braking index and characteristic spin- down timescale, iv) the fraction of spin-down power going to cosmic-ray electrons and positrons and v) their propagation through the interstellar medium and the Heliosphere. We find that middle aged pulsars have a braking index that on average has to be 3 or larger. Given that electromagnetic spectrum observations of young pulsars find braking indices lower than 3, our work provides strong hints that pulsars' braking index increases on average as they age, allowing them to retain some of their rotational energy. Moreover, we find that pulsars have relatively uniform properties as sources of cosmic-ray electrons and positrons in terms of the spectra they produce and likely release O$(10\%)$ of their rotational energy to cosmic-rays in the ISM. Finally, we find at about 12 GeV positrons a spectral feature that suggests a new subpopulation of positron sources contributing at these energies. |
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