Session SD: Nuclear Astrophysics VI

Covariant density functional theory input for r-process simulations in actinides and superheavy nuclei: the ground state and fission properties

The systematic investigation of the ground state and fission properties of even-even actinides and superheavy nuclei with $Z=90-120$ from the two-proton up to two-neutron drip lines with proper assessment of systematic theoretical uncertainties has been performed for the first time in the framework of covariant density functional theory (CDFT). These results provide a necessary theoretical input for the r-process modeling in heavy nuclei. Four state-of-the-art globally tested covariant energy density functionals (CEDFs), namely, DD-PC1, DD-ME2, NL3* and PC-PK1, representing the major classes of the CDFT models are employed in the present study. Theoretical uncertainties in the ground state deformations and fission barriers and their evolution as a function of proton and neutron numbers have been quantified and their major sources have been identified. Spherical shell closures at $Z=120$, $N=184$ and $N=258$ as well as nuclear matter properties of employed CEDFs are two major factors contributing into theoretical uncertainties.   

Hyperon Bulk Viscosity in Neutron Star Mergers

We present a complete computation of bulk viscosity due to hyperonic processes in matter at densities and temperatures typical of neutron star mergers. To deal with the high temperatures in this environment our rate calculations go beyond the Fermi surface approximation and evaluate the full phase space integral. We obtain the damping times for harmonic oscillations at the frequencies seen in merger simulations, and find that hyperon bulk viscosity can be highly relevant at densities around the onset of the first hyperon species and temperatures up to $T=5$ MeV, with damping times as low as $\tau_{\mathrm{damp}}\approx 9$ ms.   

Mirror Neutron Stars

The potential for the discovery of exotic compact objects using gravitational wave observatories motivates the investigation of Mirror Neutron Stars. Mirror matter can occur in many well-motivated particle physics models, can be a subcomponent of dark matter and can be very weakly interacting with Standard Model matter. The simplest realisation of mirror matter results in a scaling-up of the masses of the quarks and leptons, resulting in a dark QCD sector with a higher confinement scale and heavier bound states. We use a simple model of the nuclear equation of state for Mirror QCD and discuss observable characteristics of Mirror Neutron Stars, including their mass-radius relationship, I-Love-Q relations, etc. We show that our results and predictions for the properties of Mirror Neutron Stars are robust even given uncertainties concerning the nuclear equation of state. Given the future reach of gravitational   

New methods for the equation of state of neutron stars

The equation of state (EOS) of hot and dense matter is crucial for our understanding of neutron stars, neutron-star mergers, and core-collapse supernovae. In recent years, effective field theory methods have enabled systematic calculations of the low-density EOS with controlled uncertainties. Further, new constraints for the high-density EOS have been extracted from neutron-star observations and QCD computations. These advances make it possible to approach the construction of astrophysical equations of state as a constrained extrapolation problem (CEP). In this talk, we develop a new method for the CEP. We apply the method to the universal dilute Fermi gas with strong interactions and find that it yields accurate approximations that agree with exact results [1,2]. We then set up a CEP-type construction for the EOS for astrophysical applications, and develop new equations of state that are consistent with nuclear physics, observations and high-density QCD calculations [3]. [1] C. Wellenhofer, C. Drischler, A. Schwenk, Phys.Lett.B 802 (2020) [2] C. Wellenhofer, D.R. Phillips, A. Schwenk, arXiv:2006.01429 [3] S. Huth, C. Wellenhofer, A. Schwenk, in preparation   

Nuclear and neutron-star matter from local chiral interactions

The nuclear equation of state (EOS) is of great interest for nuclear physics and nuclear astrophysics. At different proton fractions, the EOS sets the bulk properties of atomic nuclei and the properties of neutron stars. The energy difference of nuclear matter at different proton fractions is governed by the nuclear symmetry energy. The nuclear symmetry energy is a fundamental quantity that affects a range of neutron-star properties and is deeply connected to properties of atomic nuclei. Understanding the properties of the nuclear EOS has recently become even more critical with the advent of gravitational-wave (GW) astronomy and the first-ever detection of GWs from a binary neutron-star merger. In this talk I will present the first quantum Monte Carlo calculation of the equation of state of symmetric nuclear matter using chiral effective field theory interactions. The empirical saturation properties are well reproduced within statistical and systematic uncertainties. The symmetry energy is in good agreement with available experimentally derived constraints at saturation and twice saturation density. The corresponding pressure is also in excellent agreement with recent constraints extracted from GWs of the neutron-star merger GW170817 by the LIGO-Virgo detection.   

Why correlated effective field theory uncertainties matter: nuclear symmetry energy

In this talk, I report on the BUQEYE collaboration's [1] recent statistical analysis of correlated truncation errors in the nuclear-matter equation of state (EOS) derived from chiral effective field theory (EFT) [2,3]. Gaussian Processes with physics-based hyperparameters allow us to efficiently quantify and propagate theoretical uncertainties of the EOS to derived quantities. Specifically, I will discuss the nuclear symmetry energy to emphasize the importance of correlations between different densities and observables for robust uncertainty quantification of the EOS. \begin{itemize} \item[1)] https://buqeye.github.io/ \item[2)] Drischler, Furnstahl, Melendez, and Phillips, arXiv:2004.07232 \item[3)] Drischler, Melendez, Furnstahl, and Phillips, arXiv:2004.07805 \end{itemize}   

Reaction Screening and Weak Interactions in Hot, Magnetized Astrophysical Plasmas

Effects from high temperatures and magnetic fields on astrophysical plasmas have been investigated. Coulomb screening and weak interaction rates are found to change significantly if the temperatures and magnetic fields are high enough. For high magnetic fields, the arrangement of electron transverse momentum into Landau levels will change the characteristic plasma screening length. High fields can result in increased $\beta$-decay rates. The results found here are compelling, as thermal and magnetic field effects can affect a large number of astrophysical sites. Effects studied will be presented, and results are applied to a number of representative nucleosynthesis models. In strong magnetic fields, changes in weak interaction rates, for example, can be significant. Deviations from an ideal Fermi gas can result in a significant reduction in the plasma screening length, producing an enhancement of charged-particle reaction rates. This can have significant effects on nucleosynthesis. In addition, galactic chemical evolution signatures of nucleosynthesis in high temperatures and magnetic fields will be presented. Available modifications to commonly-used nucleosynthesis codes will be presented.   

The Implications of Our Research on Alzheimer’s

The ever increasing size of the dynamic universe in Planck lengths must rapidly alter the probabilities of the brain particles’ interactions/entanglements, and the ON/OFF information they create per the applicable references in [1]. If the idea of a female monkey to train her babies to communicate could later result in the evolution of human RNA/DNA; such a process could cause the mutation of a new virus under favorable conditions. The book [2] refers old quantum gravity by Penrose, but does not refer [1] and/or string theory, despite [1] addressing Feynman’s view, raising questions if such books can ever reflect reality. The small (quantum) gears on the cover pages of [1, 2] drive the cosmic gears of gravity. [1] Goradia SG (2019) The Quantum Theory of Entanglement and Alzheimer’s. J Alzheimer’s Neurodegener Dis 5: 023. [2] Cobb M. (2020) THE IDEA OF THE BRAIN – the past and future of neuroscience, Basic Books, New York. Key words: Quantum Entanglement, Mutation.