Nuclear Theory·nucl-th

Friday·October 22, 2021

16 papers—7 primary·9 cross-listed

08
Thermal effects on tidal deformability of a coalescing binary neutron star system
A. Kanakis-Pegios · P.S. Koliogiannis · Ch.C. Moustakidis
The study of neutron star mergers by the detection of the emitted gravitational waves is one of the most promised tools to study the properties of dense nuclear matter at high densities. It is worth claiming that, at the moment, strong evidence that the temperature of the stars is zero during the last orbits before coalescing does not exist. Contrariwise, there are some theoretical predictions suggesting that the star's temperature might even be a few MeV. According to the main theory, the tides transfer mechanical energy and angular momentum to the star at the expense of the orbit, where friction within the star converts the mechanical energy into heat. During the inspiral these effects are potentially detectable. Different treatments have been used to estimate the transfer of the mechanical energy and the size of the tidal friction, leading to different conclusions about the importance of pre-merger tidal effects. The present work is dedicated to the study of the effect of temperature on the tidal deformability of neutron stars during the inspiral of a neutron star system just before the merger. We applied a class of hot equations of state originated from various nuclear models and found that even for low values of temperature ( $T < 1$ MeV) the effects on the basic ingredients of tidal deformability are not negligible. However, according to the main finding, the effect of the temperature on the tidal deformability is indistinguishable. The consequences of this unexpected result are discussed and analyzed.
↳ astro-ph.HEnucl-thBulg.J.Phys.(2021)·0 citations
09
Nuclear data evaluation with Bayesian networks
Georg Schnabel · Roberto Capote · Arjan Koning · David Brown
Bayesian networks are graphical models to represent the probabilistic relationships between variables in the Bayesian framework. The knowledge of all variables can be updated using new information about some of the variables. We show that relying on the Bayesian network interpretation enables large scale inference and gives flexibility in incorporating prior assumptions and constraints into the nuclear data evaluation process, such as sum rules and the non-negativity of cross sections. The latter constraint is accounted for by a non-linear transformation and therefore we also discuss inference in Bayesian networks with non-linear relationships. Using Bayesian networks, the evaluation process yields detailed information, such as posterior estimates and uncertainties of all statistical and systematic errors. We also elaborate on a sparse Gaussian process construction compatible with the Bayesian network framework that can for instance be used as prior on energy-dependent model parameters, model deficiencies and energy-dependent systematic errors of experiments. We present three proof-of-concept examples that emerged in the context of the neutron data standards project and in the ongoing international evaluation efforts of $^{56}$ Fe. In the first example we demonstrate the modelization and explicit estimation of relative energy-dependent error components of experimental datasets. Then we show an example evaluation using the outlined Gaussian process construction in an evaluation of $^{56}$ Fe in the energy range between one and two MeV, where R-Matrix and nuclear model fits are difficult. Finally, we present a model-based evaluation of $^{56}$ Fe between 5 MeV and 30 MeV with a sound treatment of model deficiencies. The R scripts to reproduce the Bayesian network examples and the nucdataBaynet package for Bayesian network modeling and inference have been made publicly available.
↳ physics.data-annucl-exnucl-th3 citations
10
Axial inverse magnetic catalysis
Yuanyuan Wang🇨🇳 · Shinya Matsuzaki🇨🇳
We find that the inverse magnetic catalysis for $U (1)$ axial symmetry (AIMC: axial inverse magnetic catalysis) can emerge around the chiral crossover regime in the thermomagnetic QCD with 2 + 1 flavors at physical point. This phenomenon can be correlated with the IMC for the chiral $S U (2)_{L} \times S U (2)_{R}$ symmetry (CIMC: chiral IMC). We explicitly observe the AIMC based on a Nambu-Jona-Lasinio model with 2 + 1 quark flavors, where introduced anomalous magnetic moments of the quarks play the essential role to drive both the CIMC and AIMC. Our finding is shortly testable on lattices. Possible phenomenological and cosmological implications are also briefly addressed.
↳ hep-phhep-latnucl-thPRD(2022)·6 citations
11
Analysis of two-nucleon transfer reactions in the 20Ne + 116Cd system at 306 MeV
D. Carbone🇮🇹 · J. L. Ferreira🇧🇷 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · M. Cavallaro🇮🇹 · A. Hacisalihoglu🇹🇷 · H. Lenske🇩🇪 · J. Lubian🇧🇷 · R. I. Magana Vsevolodovna🇮🇹 · E. Santopinto🇮🇹 · C. Agodi🇮🇹 · L. Acosta🇲🇽 and 37 other authors
Background: Heavy-ion induced two-nucleon transfer reactions are powerful tools to reveal peculiar aspects of the atomic nucleus, such as pairing correlations, single-particle and collective degrees of freedom, and more. Also, these processes are in competition with the direct meson exchange in the double charge exchange reactions, which have recently attracted great interest due to their possible connection to neutrinoless double-beta decay. In this framework, the exploration of two-nucleon transfer reactions in the 20Ne+116Cd collision at energies above the Coulomb barrier is particularly relevant since the 116Cd nucleus is a candidate for the double-beta decay. Methods: We measured the excitation energy spectra and absolute cross sections for the two reactions using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. We performed direct coupled reaction channels and sequential distorted wave Born approximation calculations using the double folding São Paulo potential to model the initial and final state interactions. The spectroscopic amplitudes for two- and singleparticle transitions were derived by different nuclear structure approaches: microscopic large-scale shell model, interacting boson model-2 and quasiparticle random phase approximation. Results: The calculations are able to reproduce the experimental cross sections for both two-neutron and twoproton transfer reactions. The role of couplings with the inelastic channels are found to be important in the two-proton transfer case. A competition between the direct and the sequential process is found in the reaction mechanism. For the two-proton transfer case, the inclusion of the 1g7/2 and 2d5/2 orbitals in the model space is crucial.
↳ nucl-exnucl-thPRC(2020)·54 citations
12
Study of one-proton transfer reaction for the $^{18}$ O + $^{48}$ Ti system at 275 MeV
O. Sgouros🇮🇹 · M. Cavallaro🇮🇹 · F. Cappuzzello🇮🇹 · D. Carbone🇮🇹 · C. Agodi🇮🇹 · A. Gargano🇮🇹 · G. De Gregorio🇮🇹 · C. Altana🇮🇹 · G. A. Brischetto🇮🇹 · S. Burrello🇫🇷 · S. Calabrese🇮🇹 · D. Calvo🇮🇹 and 29 other authors
Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction $^{48}$ Ti( $^{18}$ O, $^{19}$ F) $^{47}$ Sc at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the $^{19}$ F ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the São Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space.
↳ nucl-exnucl-thPRC(2021)·41 citations
13
Entanglement Structures in Quantum Field Theories: Negativity Cores and Bound Entanglement in the Vacuum
Natalie Klco🇺🇸 · D. H. Beck🇺🇸 · Martin J. Savage🇺🇸
The many-body entanglement between two finite (size- $d$ ) disjoint vacuum regions of non-interacting lattice scalar field theory in one spatial dimension -- a $(d_{A} \times d_{B})_{mixed}$ Gaussian continuous variable system -- is locally transformed into a tensor-product "core" of $(1_{A} \times 1_{B})_{mixed}$ entangled pairs. Accessible entanglement within these core pairs exhibits an exponential hierarchy, and as such identifies the structure of dominant region modes from which vacuum entanglement could be extracted into a spatially separated pair of quantum detectors. Beyond the core, remaining modes of the "halo" are determined to be AB-separable in isolation, as well as separable from the core. However, state preparation protocols that distribute entanglement in the form of $(1_{A} \times 1_{B})_{mixed}$ core pairs are found to require additional entanglement in the halo that is obscured by classical correlations. This inaccessible (bound) halo entanglement is found to mirror the accessible entanglement, but with a step behavior as the continuum is approached. It remains possible that alternate initialization protocols that do not utilize the exponential hierarchy of core-pair entanglement may require less inaccessible entanglement. Entanglement consolidation is expected to persist in higher dimensions and may aid classical and quantum simulations of asymptotically free gauge field theories, such as quantum chromodynamics.
↳ quant-phhep-lathep-phhep-th+1PRA(2023)·35 citations
14
Accelerating quantum many-body configuration interaction with directives
Brandon Cook · Patrick J. Fasano · Pieter Maris · Chao Yang · Dossay Oryspayev
Many-Fermion Dynamics-nuclear, or MFDn, is a configuration interaction (CI) code for nuclear structure calculations. It is a platform-independent Fortran 90 code using a hybrid MPI+X programming model. For CPU platforms the application has a robust and optimized OpenMP implementation for shared memory parallelism. As part of the NESAP application readiness program for NERSC's latest Perlmutter system, MFDn has been updated to take advantage of accelerators. The current mainline GPU port is based on OpenACC. In this work we describe some of the key challenges of creating an efficient GPU implementation. Additionally, we compare the support of OpenMP and OpenACC on AMD and NVIDIA GPUs.
↳ cs.DCcs.CEcs.MScs.PF+11 citation
15
Analysis of two-proton transfer in the 40Ca(18O,20Ne)38Ar reaction at 270 MeV incident energy
J. L. Ferreira🇧🇷 · D. Carbone🇮🇹 · M. Cavallaro🇮🇹 · N. N. Deshmukh🇮🇹 · C. Agodi🇮🇹 · G. A. Brischetto🇮🇹 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · E. N. Cardozo🇧🇷 · I. Ciraldo🇮🇹 · M. Cutuli🇮🇹 · M. Fisichella🇮🇹 and 7 other authors
Two-nucleon transfer reactions are essential tools to investigate specific features of the nuclearstructure such as the correlation among valence particles in the transfer process. Besides, transfer reactions may be an important channel to take into account in charge exchange processes since they can represent a competing contribution to the final cross section. The two-proton pickup transfer reaction 40Ca(18O,20Ne)38Ar has been measured at 270 MeV and the angular distributions for transitions to different excited states extracted. This work shows the analysis of the data performed by finite range coupled reaction channel and coupled channel Born approximation methods. Extensive shell-model calculations are performed to derive the one- and two-proton spectroscopic amplitudesfor the projectile and target overlaps. The role of the simultaneous and sequential two-proton transfer mechanisms to populate the measured final states or groups of states, mainly characterized by ahigh collectivity, is also discussed.
↳ nucl-exnucl-thPRC(2021)·43 citations
16
Electron Captures and Stability of White Dwarfs
N. Chamel🇧🇪 · L. Perot🇧🇪 · A. F. Fantina🇫🇷 · D. Chatterjee🇮🇳 · S. Ghosh🇮🇳 · J. Novak🇫🇷 · M. Oertel🇫🇷
Electron captures by atomic nuclei in dense matter are among the most important processes governing the late evolution of stars, limiting in particular the stability of white dwarfs. Despite considerable progress in the determination of the equation of state of dense Coulomb plasmas, the threshold electron Fermi energies are still generally estimated from the corresponding $Q$ values in vacuum. Moreover, most studies have focused on nonmagnetized matter. However, some white dwarfs are endowed with magnetic fields reaching $1 0^{9}$ G. Even more extreme magnetic fields might exist in super Chandrasekhar white dwarfs, the progenitors of overluminous type Ia supernovae like SN 2006gz and SN 2009dc. The roles of the dense stellar medium and magnetic fields on the onset of electron captures and on the structure of white dwarfs are briefly reviewed. New analytical formulas are derived to evaluate the threshold density for the onset of electron captures for arbitrary magnetic fields. Their influence on the structure of white dwarfs is illustrated by simple analytical formulas and numerical calculations.
↳ astro-ph.SRastro-ph.HEnucl-thThe Sixteenth Marcel Grossmann Meeting, p…·1 citation

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first authorsco-authorsvia INSPIRE