Nuclear Theory·nucl-th

Wednesday·November 2, 2022

6 papers—4 primary·2 cross-listed

01
New developments in fission studies within the time-dependent density functional theory framework
Aurel Bulgac
We have extended significantly the microscopic description of the fission process by examining a larger set of observables. We extract neutron and proton numbers of fission fragments, their spins and fission fragment relative orbital angular momentum and their correlations, investigate neutrons emitted at or shortly after scission, excitation energy sharing mechanism, total kinetic energy of fission fragments, and the entanglement entropy. I will present a short overview of our simulations obtained with two independent nuclear energy density functionals.
nucl-thEPJ Web Conf.(2023)·6 citations
02
Microscopic formulation of the interacting boson model for reflection asymmetric nuclei
Kosuke Nomura
Reflection asymmetric, octupole shapes in nuclei are a prominent aspect of nuclear structure, and have been recurrently studied over the decades. Recent experiments using radioactive-ion beams have provided evidence for stable octupole shapes. A variety of nuclear models have been employed for the related theoretical analyses. We review recent studies on the nuclear octupole shapes and collective excitations within the interacting boson model. A special focus is placed on the microscopic formulation of this model by using the mean-field method that is based on the framework of nuclear density functional theory. As an illustrative example, a stable octupole deformation, and a shape phase transition as a function of nucleon number that involves both quadrupole and octupole degrees of freedom are shown to occur in light actinides. Systematic spectroscopic studies indicate enhancement of the octupole collectivity in a wide mass region. Couplings between the octupole and additional degrees of freedom are incorporated in a microscopic manner in the boson system, and shown to play a crucial role in the description of the related intriguing nuclear structure phenomena such as the shape coexistence.
nucl-thnucl-exIJMPE(2023)·6 citations
03
Ab initio no-core shell model description of $^{10 - 14}$ C isotopes
Priyanka Choudhary · Praveen C. Srivastava · Michael Gennari · Petr Navratil
We present a systematic study of the $^{10 - 14} C$ isotopes within the \textit{ab initio} no-core shell model theory. We apply four different realistic nucleon-nucleon (NN) interactions: (i) the charge-dependent Bonn 2000 (CDB2K) potential (ii) the inside non-local outside Yukawa (INOY) potential (iii) the next-to-next-to-next-to-leading order (N $^{3}$ LO) potential, and (iv) the optimized next-to-next-to-leading order (N $^{2}$ LO $_{o pt}$ ) potential. We report the low-lying energy spectra of both positive and negative parity states for the $^{10 - 14} C$ isotopes and investigate the level structures. We also calculate electromagnetic properties such as transition strengths, quadrupole and magnetic moments. The dependence of point-proton radii on the harmonic oscillator frequency and basis space is shown. We present calculations of the translation invariant one-body density matrix in the no-core shell model and discuss isotopic trends in the density distribution. The maximum basis space reached is $10ℏΩ$ for $^{10} C$ and $8ℏΩ$ for $^{11 - 14} C$ , with a maximum M-scheme dimension of $1.3 \times 1 0^{9}$ for $^{10} C$ . We found that while the INOY interaction gives the best description of the ground state energies, the N $^{3}$ LO interaction best reproduces the point-proton radii.
nucl-thnucl-exPRC(2023)·19 citations
04
Efficient few-body calculations in finite volume
S. König🇺🇸
Simulating quantum systems in a finite volume is a powerful theoretical tool to extract information about them. Real-world properties of the system are encoded in how its discrete energy levels change with the size of the volume. This approach is relevant not only for nuclear physics, where lattice methods for few- and many-nucleon states complement phenomenological shell-model descriptions and ab initio calculations of atomic nuclei based on harmonic oscillator expansions, but also for other fields such as simulations of cold atomic systems. This contribution presents recent progress concerning finite-volume simulations of few-body systems. In particular, it discusses details regarding the efficient numerical implementation of separable interactions and it presents eigenvector continuation as a method for performing robust and efficient volume extrapolations.
nucl-thJ.Phys.Conf.Ser.(2023)·6 citations
05
Bayesian analysis of neutron-star properties with parameterized equations of state: the role of the likelihood functions
Jin-Liang Jiang · Christian Ecker · Luciano Rezzolla
We have investigated the systematic differences introduced when performing a Bayesian-inference analysis of the equation of state of neutron stars employing either variable- or constant-likelihood functions. The former have the advantage that it retains the full information on the distributions of the measurements, making an exhaustive usage of the data. The latter, on the other hand, have the advantage of a much simpler implementation and reduced computational costs. In both approaches, the EOSs have identical priors and have been built using the sound-speed parameterization method so as to satisfy the constraints from X-ray and gravitational-waves observations, as well as those from Chiral Effective Theory and perturbative QCD. In all cases, the two approaches lead to very similar results and the $90%$ -confidence levels are essentially overlapping. Some differences do appear, but in regions where the probability density is extremely small and are mostly due to the sharp cutoff set on the binary tidal deformability $Λ ~ \leq 720$ employed in the constant-likelihood analysis. Our analysis has also produced two additional results. First, a clear inverse correlation between the normalized central number density of a maximally massive star, $n_{c, TOV} / n_{s}$ , and the radius of a maximally massive star, $R_{TOV}$ . Second, and most importantly, it has confirmed the relation between the chirp mass $M_{chirp}$ and the binary tidal deformability $Λ ~$ . The importance of this result is that it relates a quantity that is measured very accurately, $M_{chirp}$ , with a quantity that contains important information on the micro-physics, $Λ ~$ . Hence, once $M_{chirp}$ is measured in future detections, our relation has the potential of setting tight constraints on $Λ ~$ .
↳ gr-qcastro-ph.HEnucl-thApJ(2023)·72 citations
06
The Width of a Beta-decay-induced Antineutrino Wavepacket
B.J.P. Jones🇺🇸 · E. Marzec🇺🇸 · J. Spitz🇺🇸
The time evolution of a neutrino is dependent on its initial properties at creation including flavor, energy, and wavepacket size. There exists no solid theoretical prediction for the latter property in the context of nuclear beta decay, despite the importance of this process for the past, present, and future of neutrino experimentation. In this paper, we provide a quantitative prediction for the size of a beta-decay-induced electron antineutrino wavepacket by treating the parent nucleus decaying to an entangled antineutrino-recoil system using the formalism of open quantum systems. Of central importance is the delocalization scale of the parent particle. We construct a systematic description of the hierarchy of localizing entanglements that provides an unambiguous statement of the relevant localization scale, found to be closely related to the diameter of the parent nucleus (e.g. $\sim$ 5-6~fm for beta-decaying fission daughters) and as low as the typical nucleon-nucleon correlation distance ( $\sim$ 1~fm). Inside a nuclear reactor, for example, this translates to initial electron antineutrino wavepacket widths in the $σ_{ν, x} \sim 10 - 400$ ~pm range for $E_{ν_{e}} > 1.8$ ~MeV, with dependencies on decaying nucleus size, the emitted antineutrino energy, and the kinematics of the recoiling system. Wavepacket sizes in this envelope do not produce an observable effect on oscillation probability in foreseeable reactor experiments in the standard three-neutrino model, including JUNO which is expected to be sensitive to $σ_{ν, x} ≲ 3$ ~pm.
↳ hep-phhep-exnucl-thPRD(2023)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE

New developments in fission studies within the time-dependent density functional theory framework

Microscopic formulation of the interacting boson model for reflection asymmetric nuclei

Ab initio no-core shell model description of 10−14C isotopes

Efficient few-body calculations in finite volume

Bayesian analysis of neutron-star properties with parameterized equations of state: the role of the likelihood functions

The Width of a Beta-decay-induced Antineutrino Wavepacket

Affiliations

Ab initio no-core shell model description of $^{10 - 14}$ C isotopes