Nuclear Theory·nucl-th

Tuesday·June 13, 2023

12 papers—9 primary·3 cross-listed

01
[Submitted on 9 Jun 2023]
Isospin Equilibration in Neutron Star Mergers
Mark G. Alford🇺🇸 · Alexander Haber🇺🇸 · Ziyuan Zhang🇺🇸
We analyze the isospin equilibration properties of neutrinoless nuclear ( $n p e$ ) matter in the temperature and density range that is relevant to neutron star mergers. Our analysis incorporates neutrino-transparency corrections to the isospin (``beta'') equilibrium condition which become noticeable at $T ≳ 1$ MeV. We find that the isospin relaxation rate rises rapidly as temperature rises, and at $T \approx 5$ MeV it is comparable to the timescale of the density oscillations that occur immediately after the merger. This produces a resonant peak in the bulk viscosity at $T \approx 5$ MeV, which causes density oscillations to be damped on the timescale of the merger. Our calculations suggest that isospin relaxation dynamics may also be relevant when neutrinos are treated more accurately via neutrino transport schemes.
Comments:
12 pages, 5 figures v2: minor changes in wording, no changes to conclusions or results of v1, version published in PRC
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2306.06180 [pdf]
PRC(2024)·40 citations
02
[Submitted on 9 Jun 2023]
Evidence against a strong first-order phase transition in neutron star cores: impact of new data
Len Brandes🇩🇪 · Wolfram Weise🇩🇪 · Norbert Kaiser🇩🇪
With the aim of exploring the evidence for or against phase transitions in cold and dense baryonic matter, the inference of the sound speed and equation-of-state for dense matter in neutron stars is extended in view of recent new observational data. The impact of the heavy (2.35 $M_{⊙}$ ) black widow pulsar PSR J0952-0607 and of the unusually light supernova remnant HESS J1731-347 is inspected. In addition a detailed re-analysis is performed of the low-density constraint based on chiral effective field theory and of the perturbative QCD constraint at asymptotically high densities, in order to clarify the influence of these constraints on the inference procedure. The trace anomaly measure, $Δ = 1/3 - P / ε$ , is also computed and discussed. A systematic Bayes factor assessment quantifies the evidence (or non-evidence) of low averaged sound speeds $(c_{s}^{2} \leq 0.1)$ , a prerequisite for a phase transition, within the range of densities realized in the core of neutron stars. One of the consequences of including PSR J0952-0607 in the data base is a further stiffening of the equation-of-state, resulting for a 2.1 solar-mass neutron star in a reduced central density of less than five times the equilibrium density of normal nuclear matter at the 68\% level. The evidence against small sound speeds in neutron star cores is further strengthened. Within the inferred 68\% posterior credible bands, only a weak first-order phase transition with a coexistence density interval $Δ n / n ≲ 0.2$ would be compatible with the observed data.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2306.06218 [pdf]
PRD(2023)·92 citations
03
[Submitted on 10 Jun 2023]
Prediction of the neutron drip line in oxygen isotopes using quantum computation
Chandan Sarma🇮🇳 · Olivia Di Matteo🇨🇦 · Abhishek Abhishek🇨🇦 · Praveen C. Srivastava🇮🇳
In the noisy intermediate-scale quantum era, variational algorithms have become a standard approach to solving quantum many-body problems. Here, we present variational quantum eigensolver (VQE) results of selected oxygen isotopes within the shell model description. The aim of the present work is to locate the neutron drip line of the oxygen chain using unitary coupled cluster (UCC) type ansatze with different microscopic interactions (DJ16, JISP16, and N3LO), in addition to a phenomenological USDB interaction. While initially infeasible to execute on contemporary quantum hardware, the size of the problem is reduced significantly using qubit tapering techniques in conjunction with custom circuit design and optimization. The optimal values of ansatz parameters from classical simulation are taken for the DJ16 interaction, and the tapered circuits are run on IonQ's Aria, a trapped-ion quantum computer. After applying gate error mitigation for three isotopes, we reproduced exact ground state energies within a few percent error. The post-processed results from hardware also clearly show $^{24}$ O as the drip line nucleus of the oxygen chain. Future improvements in quantum hardware could make it possible to locate drip lines of heavier nuclei.
Comments:
13 pages, 10 figures, 8 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex); Quantum Physics (quant-ph)
arXiv:
2306.06432 [pdf]
PRC(2023)·39 citations
04
[Submitted on 11 Jun 2023]
Continuum-discretized coupled-channel calculations for $^{6}$ Li fusion reactions with closed channels
Wendi Chen · D.Y. Pang · Hairui Guo · Ye Tao · Weili Sun · Yangjun Ying
Fusion reactions induced by the weakly bound nucleus $^{6}$ Li with targets $^{28}$ Si, $^{64}$ Ni, $^{144}$ Sm and $^{209}$ Bi at energies around the Coulomb barrier are investigated within a three-body model where $^{6}$ Li is described with an $α + d$ cluster model. The total fusion (TF) cross sections are calculated with the continuum-discretized coupled-channel (CDCC) method and the complete fusion (CF) cross sections are extracted through the sum-rule model. The calculations demonstrate that (i) for the TF cross section calculations, the continuum states up to 40 MeV are found to be necessary, which corresponds to the inclusion of closed channels for light and medium mass targets, such as $^{28}$ Si, $^{59}$ Co and $^{144}$ Sm, (ii) the converged CDCC results for TF cross section at energies above the Coulomb barrier are almost the same as single channel results in which the continuum coupling effect is neglected, and (iii) the continuum coupling strongly influences partial wave fusion cross sections and the closed channels play a significant role in the improvement of the description of the CF cross sections at energies below the Coulomb barrier for the $^{6}$ Li+ $^{28}$ Si, $^{59}$ Co and $^{144}$ Sm systems.
Comments:
15 pages; 23 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2306.06621 [pdf]
PRC(2023)·5 citations
05
[Submitted on 11 Jun 2023]
Complex valence-space effective operators for observables: the Gamow-Teller transition
Z. C. Xu · S. Zhang · J. G. Li · S. L. Jin · Q. Yuan · Z. H. Cheng · N. Michel · F. R. Xu
Nuclei in the vicinity of driplines have been receiving a lot of attention in nuclear structure studies. In the nuclei, the continuum coupling is crucial in reproducing weakly-bound and unbound phenomena. To calculate observables of the nuclei as open quantum systems, we have developed valence-space effective operators in the complex-energy Berggren basis using many-body perturbation theory. We focus on the Gamow-Teller $β$ decay in the {\it sd} shell. The two- plus three-nucleon force from the chiral effective field theory (EFT), named EM1.8/2.0, has been used. The Gamow shell model which takes the continuum coupling into account can properly reproduce experimental observations of weakly-bound and unbound states. The $β$ -decay isospin asymmetry between the dripline nucleus $^{22} Si$ and its mirror partner $^{22} O$ is reproduced, in which the $s_{1/2}$ continuum plays a key role. Significant Thomas-Ehrman shift is seen through mirror energy differences between the mirror daughters $^{22} Al$ and $^{22} F$ , in which the continuum effect plays an important role.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2306.06692 [pdf]
PRC(2023)·16 citations
06
[Submitted on 12 Jun 2023]
Correlation of density fluctuation in a magnetized QCD matter near the critical end point
Mahfuzur Rahaman🇮🇳 · Md Hasanujjaman🇮🇳 · Golam Sarwar🇮🇳 · Abhijit Bhattacharyya🇮🇳 · Jan-e Alam🇮🇳
The dynamical correlation of density fluctuation in quark gluon plasma with a critical end point has been investigated within the scope of the Müller-Israel-Stewart theory in the presence of static ultra-high external magnetic field. The dynamic structure factor of the density fluctuation exhibits three Lorentzian peaks in absence of external magnetic field- a central Rayleigh peak and two Brillouin peaks situated symmetrically on the opposite sides of the Rayleigh peak. The spectral structure displays five peaks in presence of the magnetic field due to the coupling of the magnetic field with the hydrodynamic fields in second-order hydrodynamics. The emergence of the extra peaks is due to the asymmetry in the pressure gradient caused by the external magnetic field in the system. Interestingly, it is observed that near the critical end point, all the Brillouin peaks disappear irrespective of the presence or absence of the external magnetic field.
Comments:
Matches published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2306.06905 [pdf]
EPJC(2024)·2 citations
07
[Submitted on 12 Jun 2023]
Decoding Neutron Star Observations: Revealing Composition through Bayesian Neural Networks
Valéria Carvalho🇵🇹 · Márcio Ferreira🇵🇹 · Tuhin Malik🇵🇹 · Constança Providência🇵🇹
We exploit the great potential offered by Bayesian Neural Networks (BNNs) to directly decipher the internal composition of neutron stars (NSs) based on their macroscopic properties. By analyzing a set of simulated observations, namely NS radius and tidal deformability, we leverage BNNs as effective tools for inferring the proton fraction and sound speed within NS interiors. To achieve this, several BNNs models were developed upon a dataset of $\sim$ 25K nuclear EoS within a relativistic mean-field framework, obtained through Bayesian inference that adheres to minimal low-density constraints. Unlike conventional neural networks, BNNs possess an exceptional quality: they provide a prediction uncertainty measure. To simulate the inherent imperfections present in real-world observations, we have generated four distinct training and testing datasets that replicate specific observational uncertainties. Our initial results demonstrate that BNNs successfully recover the composition with reasonable levels of uncertainty. Furthermore, using mock data prepared with the DD2, a different class of relativistic mean-field model utilized during training, the BNN model effectively retrieves the proton fraction and speed of sound for neutron star matter.
Comments:
16 pages, 15 figures, published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2306.06929 [pdf]
PRD(2023)·28 citations
08
[Submitted on 12 Jun 2023]
$Λ$ hypernuclear potentials beyond linear density dependence
E. Friedman🇮🇱 · A. Gal🇮🇱
In a recent paper [PLB 837 (2023) 137669] we showed that all measured ( $1 s_{Λ}$ , $1 p_{Λ}$ ) pairs of $Λ$ binding energies in $Λ$ -hypernuclei across the periodic table, $12 \leq A \leq 208$ , can be obtained from a $Λ$ -nucleus optical potential with only two adjustable $Λ N$ and $Λ N N$ parameters, associated with leading linear and quadratic terms in the nuclear density, derived by fitting $_{Λ}^{16}$ N binding energies. Here we extend the previous analysis by performing least-squares fits to the full set of data points. Consequences of suppressing $Λ N N$ interactions between `core' nucleons and `excess' neutrons are studied and related predictions are made for ( $1 s_{Λ}$ , $1 p_{Λ}$ ) binding energies in $_{Λ}^{40, 48}$ K, obtainable from upcoming $^{40, 48}$ Ca( $e, e^{'} K^{+}$ ) JLab experiments. We find $Λ$ -nucleus partial potential depths of $D_{Λ}^{(2)} = - 38.6 \pm 0.8$ ~MeV ( $Λ N$ ) and $D_{Λ}^{(3)} = 11.3 \pm 1.4$ ~MeV ( $Λ N N$ ), with a total depth $D_{Λ} = - 27.3 \pm 0.6$ ~MeV at nuclear-matter density $ρ_{0}$ =0.17~fm $^{- 3}$ , consistently with our previous results. Extrapolation to higher nuclear densities and possible relevance to the `hyperon puzzle' in neutron-star matter are discussed.
Comments:
19 pages, 7 figures, 4 tables, minor changes, published in Nucl. Phys. A 1039 (2023) 122725; doi.org/10.1016/j.nuclphysa.2023.122725
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2306.06973 [pdf]
NPA(2023)·26 citations
09
[Submitted on 12 Jun 2023]
Derivation of transition density from the observed 4He(e,e')4He(0^+_2) form factor raising the alpha-particle monopole puzzle
Masayasu Kamimura
Recently, the monopole transition form factor of the electron-scattering excitation of the 0^+_2 state (E_x=20.21 MeV) of the 4He nucleus was observed over a broad momentum transfer range (0.5 < q^2 < 5.0 fm^-2) with dramatically improved preision compared with older sets of data; modern nuclear forces, including those derived from the chiral effective field theory, failed to reproduce the form factor, which is called the alpha-particle monopole puzzle. To resolve this puzzle by improving the study of spatial structure of the 0^+_2 state, we derive in this letter a possible 0^+_1 --> 0^+_2 transition density \rho_tr(r) for r > 1 fm from the observed form factor. The shape of the transition density is significantly different from that obtained theoretically in the literature
Comments:
13 pages, 6 figures, minor changes in descriptions, published virsion
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2306.07268 [pdf]
PTEP(2023)·2 citations
10
[Submitted on 26 May 2023] (cross-list from astro-ph.HE)
Pulsar as a Weber detector of gravitational waves and a probe to its internal phase transitions
Partha Bagchi🇮🇳 · Oindrila Ganguly🇮🇳 · Biswanath Layek🇮🇳 · Anjishnu Sarkar🇮🇳 · Ajit M. Srivastava🇮🇳
It is believed that cores of neutron stars provide a natural laboratory where exotic high baryon density QCD phases may exist.The theoretically well established {\it neutron superfluid phase} is also believed to be found only inside neutron stars. Focus on neutron stars has intensified in recent years with the direct detection of gravitational waves (GWs) from binary neutron star (BNS) merger, which has allowed the possibility of directly probing the properties of the interior of a neutron star. A remarkable phenomenon manifested by rapidly rotating neutron stars is in their {\it avatar} as {\it Pulsars}. The accuracy of pulsar timing allowed the first indirect detection of GWs from a BNS system and opened up a few exciting possibilities. Any pulsar deformation, even if incredibly tiny, can leave imprints on the pulses by introducing tiny perturbations of the moment of inertia (MI) tensor components. While the diagonal MI components of the perturbed MI tensor affect the pulse timings, the off-diagonal components lead to the pulsar's wobbling and affecting the pulse profile. This opens up an opportunity to explore various phase transitions inside a pulsar core by induced density fluctuations through the observable effects on the pulse timing and profile. Such perturbations also naturally induce a rapidly changing quadrupole moment of the star, thereby providing a new source of GW emission. Another remarkable possibility arises when we consider the effect of an external GW on a neutron star. With the possibility of detecting any minute changes in its configuration through pulse observations, the neutron star has the potential to perform as a Weber detector of GWs. This brief review focuses on these specific aspects of a pulsar, specifically on the type of physics that can be probed by utilizing the effect of changes in the MI tensor on pulse properties.
Comments:
Review article (revised), 31 pages, title changed, abstract reduced, fig.6 is corrected (larger fonts), references added, accepted for publication in Modern Physics Letters A (MPLA)
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2305.16850 [pdf]
Mod.Phys.Lett.A(2024)·5 citations
11
[Submitted on 9 Jun 2023] (cross-list from physics.comp-ph)
On the unimportance of memory for the time non-local components of the Kadanoff-Baym equations
Cian C. Reeves · Yuanran Zhu · Chao Yang · Vojtech Vlcek
The generalized Kadanoff-Baym ansatz (GKBA) is an approximation to the Kadanoff-Baym equations (KBE), that neglects certain memory effects that contribute to the Green's function at non-equal times. Here we present arguments and numerical results to demonstrate the practical insignificance of the quantities neglected when deriving the GKBA at conditions at which KBE and GKBA are appropriate. We provide a mathematical proof that places a scaling bound on the neglected terms, further reinforcing that these terms are typically small in comparison to terms that are kept in the GKBA. We perform calculations in a range of models, including different system sizes and filling fractions, as well as experimentally relevant non-equilibrium excitations. We find that both the GKBA and KBE capture the dynamics of interacting systems with moderate and even strong interactions well. We explicitly compute terms neglected in the GKBA approximation and show, in the scenarios tested here, that they are orders of magnitude smaller than the terms that are accounted for, i.e., they offer only a small correction when included in the full Kadanoff-Baym equations.
Comments:
14 pages, 3 figures, Supplemental information with 10 figures
Subjects:
Computational Physics (physics.comp-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2306.06225 [pdf]
PRB(2023)·4 citations
12
[Submitted on 12 Jun 2023] (cross-list from hep-lat)
Dynamics of the $O (4)$ critical point in QCD: critical pions and diffusion in Model G
Adrien Florio🇺🇸 · Eduardo Grossi🇮🇹 · Derek Teaney🇺🇸
We present a detailed study of the finite momentum dynamics of the $O (4)$ critical point of QCD, which lies in the dynamic universality class of Model G. The critical scaling of the model is analyzed in multiple dynamical channels. For instance, the finite momentum analysis allows us to precisely extract the pion dispersion curve below the critical point. The pion velocity is in striking agreement with the predictions relation and static universality. The pion damping rate and velocity are both consistent with the dynamical critical exponent $ζ = 3/2$ of Model G. Similarly, although the critical amplitude for the diffusion coefficient of the conserved $O (4)$ charges is small, it is clearly visible both in the restored phase and with finite explicit symmetry breaking, and its dynamical scaling is again consistent with $ζ = 3/2$ . We determine a new set of universal dynamical critical amplitude ratios relating the diffusion coefficient to a suitably defined order parameter relaxation time. We also show that in a finite volume simulation, the chiral condensate diffuses on the coset manifold in a manner consistent with dynamical scaling, and with a diffusion coefficient that is determined by the transport coefficients of hydrodynamic pions. Finally, the amplitude ratios (together with other non-universal amplitudes also reported here) compile all relevant information for further studies of Model G both in and out of equilibrium.
Comments:
34 pages, 13 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2306.06887 [pdf]
PRD(2024)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE