Nuclear Theory·nucl-th

Friday·June 16, 2023

23 papers—11 primary·12 cross-listed

01
Neutron star matter based on a parity doublet model including the $a_{0} (980)$ meson
Yuk Kei Kong🇯🇵 · Takuya Minamikawa🇯🇵 · Masayasu Harada🇯🇵
We study the effect of the isovector-scalar meson $a_{0}$ (980) on the properties of nuclear matter and the neutron star (NS) matter by constructing a parity doublet model with including the $a_{0}$ meson based on the chiral SU(2) $_{L} \times$ SU(2) $_{R}$ symmetry. We also include the $ω$ - $ρ$ mixing contribution to adjust the slope parameter at the saturation. We find that, when the chiral invariant mass of nucleon $m_{0}$ is smaller than about 800 MeV, the existence of $a_{0}$ (980) enlarges the symmetry energy by strengthening the repulsive $ρ$ meson coupling. On the other hand, for large $m_{0}$ where the Yukawa coupling of $a_{0}$ (980) to nucleon is small, the symmetry energy is reduced by the effect of $ω$ - $ρ$ mixing. We then construct the equation of state (EoS) of a neutron star matter to obtain the mass-radius relation of NS. We find that, in most choices of $m_{0}$ , the existence of $a_{0}$ (980) stiffens the EoS and makes the radius of NS larger. We then constrain the chiral invariant mass of nucleon from the observational data of NS, and find that $580 MeV ≲ m_{0} ≲ 860 MeV$ for $L_{0} = 57.7$ MeV.
nucl-thastro-ph.HEhep-phPRC(2023)·24 citations
02
Classical and Bayesian error analysis of the relativistic mean-field model for doubly magic nuclei
M. Imbrišak · K. Nomura
The information-geometric statistical analysis on the stability of model reductions, reported previously [Imbrišak and Nomura, Phys. Rev. C 107, 034304 (2023)] with a focus on the manifold boundary approximation method in the application to the nuclear density-dependent point-coupling model of infinite nuclear matter, is extended to the numerically more challenging case of finite nuclei. A simple procedure is presented for determining the binding energies of doubly magic nuclei within the relativistic mean-field framework using the Woods-Saxon potential. The proposed procedure, employing the Fisher information matrix combined with algorithmic differentiation, is shown to provide reliable estimates of parameter uncertainties of the nuclear energy density functional for finite nuclei, while reducing the time-consuming sampling of the parameter space, which would be required in the numerically more involved Bayesian statistical techniques.
nucl-thPRC(2023)·2 citations
03
Core States of Neutron Stars from Anatomizing their Scaled Structure Equations
Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸 · Zhen Zhang🇨🇳
Given an Equation of State (EOS) for neutron star (NS) matter, there is a unique mass-radius sequence characterized by a maximum mass $M_{NS}^{m a x}$ at radius $R_{m a x}$ . We first show analytically that the $M_{NS}^{m a x}$ and $R_{m a x}$ scale linearly with two different combinations of NS central pressure $P_{c}$ and energy density $ε_{c}$ by dissecting perturbatively the dimensionless Tolman-Oppenheimer-Volkoff (TOV) equations governing NS internal variables. The scaling relations are then verified via 87 widely used and rather diverse phenomenological as well as 17 microscopic NS EOSs with/without considering hadron-quark phase transitions and hyperons by solving numerically the original TOV equations. The EOS of densest NS matter allowed before it collapses into a black hole (BH) is then obtained. Using the universal $M_{NS}^{m a x}$ and $R_{m a x}$ scalings and NICER (Neutron Star Interior Composition Explorer) and XMM-Newton mass-radius observational data for PSR J0740+6620, a very narrow constraining band on the NS central EOS is extracted directly from the data for the first time without using any specific input EOS model.
nucl-thastro-ph.HEnucl-exApJ(2023)·24 citations
04
Generative deep-learning reveals collective variables of Fermionic systems
Raphaël-David Lasseri · David Regnier · Mikaël Frosini · Marc Verriere · Nicolas Schunck
Complex processes ranging from protein folding to nuclear fission often follow a low-dimension reaction path parameterized in terms of a few collective variables. In nuclear theory, variables related to the shape of the nuclear density in a mean-field picture are key to describing the large amplitude collective motion of the neutrons and protons. Exploring the adiabatic energy landscape spanned by these degrees of freedom reveals the possible reaction channels while simulating the dynamics in this reduced space yields their respective probabilities. Unfortunately, this theoretical framework breaks down whenever the systems encounters a quantum phase transition with respect to the collective variables. Here we propose a generative-deep-learning algorithm capable of building new collective variables highly representative of a nuclear process while ensuring a differentiable mapping to its Fermionic wave function. Within this collective space, the nucleus can evolve continuously from one of its adiabatic quantum phase to the other at the price of crossing a potential energy barrier. This approach applies to any Fermionic system described by a single Slater determinant, which encompasses electronic systems described within the density functional theory.
nucl-thquant-phPRC(2024)·5 citations
05
Manipulation of Giant Multipole Resonances via Vortex $γ$ Photons
Zhi-Wei Lu · Liang Guo · Zheng-Zheng Li · Mamutjan Ababekri · Fang-Qi Chen · Changbo Fu · Chong Lv · Ruirui Xu · Xiangjin Kong · Yi-Fei Niu · Jian-Xing Li
Traditional photonuclear reactions primarily excite giant dipole resonances, making the measurement of isovector giant resonances with higher multipolarties a great challenge. In this work, the manipulation of collective excitations of different multipole transitions in nuclei via vortex $γ$ photons has been investigated. We develop the calculation method for photonuclear cross sections induced by the vortex $γ$ photon beam using the fully self-consistent random-phase approximation plus particle-vibration coupling (RPA+PVC) model based on Skyrme density functional. We find that the electromagnetic transitions with multipolarity $J < m_{γ}$ are forbidden for vortex $γ$ photons due to the angular momentum conservation, with $m_{γ}$ being the projection of total angular momentum of $γ$ photon on its propagation direction. For instance, this allows for probing the isovector giant quadrupole resonance without interference from dipole transitions using vortex $γ$ photons with $m_{γ} = 2$ . The electromagnetic transitions with $J > m_{γ}$ are strongly suppressed compared with the plane-wave- $γ$ -photon case, and even vanish at specific polar angles. Therefore, the giant resonances with specific multipolarity can be extracted via vortex $γ$ photons. Moreover, the vortex properties of $γ$ photons can be meticulously diagnosed by measuring the nuclear photon-absorption cross section. Our method opens new avenues for photonuclear excitations, generation of coherent $γ$ photon laser and precise detection of vortex particles, and consequently, has significant impact on nuclear physics, nuclear astrophysics and strong laser physics.
nucl-thPRL(2023)·50 citations
06
Stochastic fluctuations in relativistic fluids: causality, stability, and the information current
Nicki Mullins (Illinois U., Urbana)🇺🇸 · Mauricio Hippert (Illinois U., Urbana)🇺🇸 · Jorge Noronha (Illinois U., Urbana)🇺🇸
We develop a general formalism for introducing stochastic fluctuations around thermodynamic equilibrium which takes into account, for the first time, recent developments on the causality and stability properties of relativistic hydrodynamic theories. The method is valid for any covariantly stable theory of relativistic viscous fluid dynamics derived from a covariant maximum entropy principle. We illustrate the formalism with some applications, showing how it could be used to consistently introduce fluctuations in a model of relativistic heat diffusion, and in conformally invariant Israel-Stewart theory in a general hydrodynamic frame. The latter example is used to study the hydrodynamic frame dependence of the symmetric two-point function of fluctuations of the energy-momentum tensor.
nucl-thhep-phhep-thPRD(2023)·25 citations
07
Bayesian parameter estimation with a new three-dimensional initial-conditions model for ultrarelativistic heavy-ion collisions
Derek Soeder🇺🇸 · Weiyao Ke🇺🇸 · J.-F. Paquet🇺🇸 · Steffen A. Bass🇺🇸
We extend the well-studied midrapidity TRENTo initial-conditions model to three dimensions, thus facilitating (3+1)D modeling and analysis of ultrarelativistic heavy-ion collisions at RHIC and LHC energies. TRENTo-3D is a fast, parametric model of the 3D initial-state geometry, capable of providing initial conditions for (3+1)D models of quark--gluon plasma formation and evolution. It builds on TRENTo's success at modeling the initial nuclear participant thicknesses, longitudinally extending the initial deposition to form a central fireball near midrapidity and two fragmentation regions at forward and backward rapidities. We validate the new model through a large-scale Bayesian calibration, utilizing as observables the rapidity distributions of charged hadrons. For computational efficiency the present effort employs a (1+1)D linearized approximation of ideal hydrodynamics as a stand-in for quark--gluon plasma dynamics. This calibration serves as model validation and paves the way for utilizing TRENTo-3D as an initial-conditions model for state-of-the-art simulation incorporating (3+1)D relativistic viscous hydrodynamics.
nucl-th28 citations
08
IMSRG-Net: A machine learning-based solver for In-Medium Similarity Renormalization Group
Sota Yoshida
We present a novel method, IMSRG-Net, which utilizes machine learning techniques as a solver for the in-medium Similarity Renormalization Group (IMSRG). The primary objective of IMSRG-Net is to approximate the Magnus operators $Ω (s)$ in the IMSRG flow equation, thereby offering an alternative to the computationally intensive part of IMSRG calculations. The key idea of IMSRG-Net is its design of the loss function inspired by physics-informed neural networks to encode the underlying {\it physics}, i.e., IMSRG flow equation, into the model. Through training on a dataset comprising ten data points with flow parameters up to $s = 20$ , capturing approximately one-eighth to one-quarter of the entire flow, IMSRG-Net exhibits remarkable accuracy in extrapolating the ground state energies and charge radii of $^{16}$ O and $^{40}$ Ca. Furthermore, this model demonstrates effectiveness in deriving effective interactions for a valence space.
nucl-thphysics.comp-phPRC(2023)·3 citations
09
Revisiting the extraction of charge radii of $^{40}$ Ca and $^{208}$ Pb with muonic atom spectroscopy
Hui Hui Xie🇨🇳 · Tomoya Naito🇯🇵 · Jian Li🇨🇳 · Haozhao Liang🇯🇵
The extractions of nuclear charge radii from muonic atom spectroscopy for $^{40}$ Ca and $^{208}$ Pb are revisited to analyze the model dependencies induced by employing a Fermi-type charge distribution. For that, the charge densities, together with the corresponding muonic transition energies, calculated by the covariant density functional theory are used as a benchmark. The root-mean-square deviation of transition energies is calculated to quantitatively investigate the sensitivities of transition energies to the details of the two-parameter Fermi distribution. It is found that the second and fourth moments of the charge distribution can be extracted accurately from the muonic atom spectroscopy without much model dependencies, whereas the obtained two-parameter Fermi distributions cannot reproduce the details of the benchmarking charge densities and, in particular, its surface-diffuseness parameter cannot be determined accurately with the present experimental uncertainties on the muonic transition energies.
nucl-thnucl-exPLB(2023)·10 citations
10
Robust universal relations in neutron star asteroseismology
Deepak Kumar🇮🇳 · Tuhin Malik🇵🇹 · Hiranmaya Mishra🇮🇳 · Constança Providência🇵🇹
The non-radial oscillations of the neutron stars (NSs) have been suggested as a useful tool to probe the composition of neutron star matter (NSM). With this scope in mind, we consider a large number of equations of states (EOSs) that are consistent with nuclear matter properties and pure neutron matter EOS based on a chiral effective field theory (chEFT) calculation for the low densities and perturbative QCD EOS at very high densities. This ensemble of EOSs is also consistent with astronomical observations, gravitational waves in GW170817, mass and radius measurements from Neutron star Interior Composition ExploreR (NICER). We analyze the robustness of known universal relations (URs) among the quadrupolar $f$ mode frequencies, masses and radii with such a large number of EOSs and we find a new UR that results from a strong correlation between the $f$ mode frequencies and the radii of NSs. Such a correlation is very useful in accurately determining the radius from a measurement of $f$ mode frequencies in the near future. We also show that the quadrupolar $f$ mode frequencies of NS of masses 2.0 M $_{⊙}$ and above lie in the range $\sim$ 2-3 kHz in this ensemble of physically realistic EOSs. A NS of mass 2M $_{⊙}$ with a low $f$ mode frequency may indicate the existence of non-nucleonic degrees of freedom.
nucl-thastro-ph.HEgr-qchep-thPRD(2023)·13 citations
11
Non-Gaussian transverse momentum fluctuations from impact parameter fluctuations
Rupam Samanta🇵🇱 · João Paulo Picchetti🇧🇷 · Matthew Luzum🇧🇷 · Jean-Yves Ollitrault🇫🇷
The transverse momentum per particle, $[p_{t}]$ , fluctuates event by event in ultrarelativistic nucleus-nucleus collisions, for a given multiplicity. These fluctuations are small and approximately Gaussian, but a non-zero skewness has been predicted on the basis of hydrodynamic calculations, and seen experimentally. We argue that the mechanism driving the skewness is that, if the system thermalizes, the mean transverse momentum increases with impact parameter for a fixed collision multiplicity. We postulate that fluctuations are Gaussian at fixed impact parameter, and that non-Gaussianities solely result from impact parameter fluctuations. Using recent data on the variance of $[p_{t}]$ fluctuations, we make quantitative predictions for their skewness and kurtosis as a function of the collision multiplicity. We predict in particular a spectacular increase of the skewness below the knee of the multiplicity distribution, followed by a fast decrease.
nucl-thhep-exhep-phnucl-exPRC(2023)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE