Nuclear Theory·nucl-th

Tuesday·April 27, 2021

14 papers—6 primary·8 cross-listed

01
Glassy quantum nuclear pasta in neutron star crusts
William G. Newton · Mark Alexander Kaltenborn · Sarah Cantu · Shuxi Wang · Amber Stinson · Jirina Rikovska Stone
We investigate the nuclear pasta phases in neutron star crusts by conducting a large number of three-dimensional Hartree-Fock+BCS calculations at densities leading to the crust-core transition. We survey the shape parameter space of pasta at constant pressure. Spaghetti, waffles, lasagna, bi-continuous phases and cylindrical holes occupy local minima in the resulting Gibbs energy surfaces. The bi-continuous phase, in which both the neutron gas and nuclear matter extend continuously in all dimensions and therefore protons are delocalized, appears over a large range of depths. Our results support the idea that nuclear pasta is a glassy system. Multiple pasta configurations coexist in a given layer of the crust. At a characteristic temperature, of order $1 0^{8}$ - $1 0^{9}$ K, different phases become frozen into domains whose sizes we estimate to be 1-50 times the lattice spacing and over which the local density and electron fraction can vary. Above this temperature, there is very little long-range order and matter is an amorphous solid. Electron scattering off domain boundaries may contribute to the disorder resistivity of the pasta phases. Annealing of the domains may occur during cooling; repopulating of local minima during crustal heating might lead to temperature dependent transport properties in the deep layers of the crust. We identify 4 distinct regions: (1) nuclear pasta first appears as a local minima, but spherical nuclei are the ground state; (2) nuclear pasta become the absolute minimum, but spherical nuclei are still a local minimum (3) only nuclear pasta appears in local minima, and protons are still localized in at least one dimension (4) only pasta appears, and protons are delocalized. The whole pasta region can occupy up to 70% of the crust by mass and 40% by thickness, and the layer in which protons are delocalized could occupy 45% of the crust mass and 25% of its thickness.
nucl-thastro-ph.HEastro-ph.SRPRC(2022)·37 citations
02
Symmetry energy extracted from the S $π$ RIT pion data in Sn+Sn systems
Gao-Chan Yong🇨🇳
With the improved particular Isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model (impIBUU) including the nucleon-nucleon short-range correlations, the ratios and yields of $π^{-}$ and $π^{+}$ in Sn+Sn systems with different asymmetries at 270 MeV/nucleon are studied. It is found that the yields of $π^{-}$ and $π^{+}$ and their ratios in Sn+Sn systems characterized by different neutron to proton ratios obtained from the very recent S $π$ RIT pion data, are quite well described by the model, especially when a soft symmetry energy with $L (ρ_{0})$ = 66.75 $\pm$ 24.75 MeV is used. The calculations also clearly demonstrate that the high-momentum tail of the nucleon initialization in momentum space strongly affects the yields and ratios of pion production in Sn+Sn systems with different asymmetries near or below threshold. In addition, given many insoluble theoretical uncertainties in transport models, multi-system experimental measurements with various N/Z asymmetries are proposed to extract the symmetry energy less model-dependently by using heavy-ion collisions.
nucl-thnucl-exPRC(2021)·24 citations
03
Relativistic resistive dissipative magnetohydrodynamics from the relaxation time approximation
Ankit Kumar Panda🇮🇳 · Ashutosh Dash🇮🇳 · Rajesh Biswas🇮🇳 · Victor Roy🇮🇳
Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution equations using the Boltzmann equation, thus extending our work from the previous paper \href{https://link.springer.com/article/10.1007/JHEP03(2021)216}{JHEP 03 (2021) 216} where we considered the non-resistive limit. We solve the Boltzmann equation for a system of particles and antiparticles using the relaxation time approximation and the Chapman-Enskog like gradient expansion for the off-equilibrium distribution function, truncating beyond second-order. In the first order, the bulk and shear stress are independent of the electromagnetic field, however, the diffusion current, shows a dependence on the electric field. In the first order, the transport coefficients~(shear and bulk stress) are shown to be independent of the electromagnetic field. The diffusion current, however, shows a dependence on the electric field. In the second-order, the new transport coefficients that couple electromagnetic field with the dissipative quantities appear, which are different from those obtained in the 14-moment approximation~\cite{Denicol:2019iyh} in the presence of the electromagnetic field. Also we found out the various components of conductivity in this case.
nucl-thhep-phphysics.flu-dynPRD(2021)·40 citations
04
Mapping Dirac--Hartree--Fock approach onto relativistic mean field model
S. Gmuca🇸🇰 · K. Petrik🇸🇰 · J. Leja🇸🇰
The exchange part of energy density of the linear Dirac--Hartree--Fock (DHF) model in symmetric nuclear matter is evaluated in a parameter--free closed form and expressed as density functional. After the rearranging terms the relativistic mean-field approach with density-dependent couplings may be recovered with density dependence coming from the Fock exchange. The formalism developed, is then extended to the nonlinear DHF approximation with field self-couplings allowed. The nonlinear self--interactions result in essential density dependence (medium modification) of effective couplings that are decoupled from the Fock ones.
nucl-thhep-thnucl-ex0 citations
05
From nuclei to neutron stars: simple binding energy computer modelling in the classroom (part 2)
A. Rios · A. Pastore · C. Diget · A. M. Romero · K. Leech · P. Stokoe
We introduce two simple online activities to explore the physics of neutron stars. These provide an introduction to the basic properties of compact objects, like their masses and radii, for secondary school students. The first activity explores the idea of the minimum mass of a neutron star. It is directly linked to the concept of binding energy and follows on from our previous activities. The second activity focuses on the maximum mass of neutron stars using a solvable model of the neutron star interior. The activities are based on spreadsheets, provided as Supplementary Material, and can be easily adapted to different levels, age groups and discussion topics. In particular, these activities can naturally lead towards discussions on extrapolations and limits of theoretical models.
nucl-thastro-ph.HEphysics.ed-ph0 citations
06
Hydrodynamic Attractor in a Hubble Expansion
Zhiwei Du🇨🇳 · Xu-Guang Huang🇨🇳 · Hidetoshi Taya🇯🇵
We analytically investigate hydrodynamic attractor solutions in both Müller-Israel-Stewart (MIS) and kinetic theories in a viscous fluid system undergoing a Hubble expansion with a fixed expansion rate. We show that the gradient expansion for the MIS theory and the Chapman-Enskog expansion for the Boltzmann equation within the relaxation time approximation are factorially divergent and obtain hydrodynamic attractor solutions by applying the Borel resummation technique to those asymptotic divergent series. In both theories, we find that the hydrodynamic attractor solutions are globally attractive and only the first-order non-hydrodynamic mode exists. We also find that the hydrodynamic attractor solutions in the two theories disagree with each other when gradients become large, and that the speed of the attraction is different. Similarities and differences from hydrodynamic attractors in the Bjorken and Gubser flows are also discussed. Our results push the idea of far-from-equilibrium hydrodynamics in systems undergoing a Hubble expansion.
nucl-thgr-qchep-phhep-thPRD(2021)·17 citations
07
Helicity Evolution at Small $x$ : the Single-Logarithmic Contribution
Yuri V. Kovchegov🇺🇸 · Andrey Tarasov🇺🇸 · Yossathorn Tawabutr🇺🇸
We calculate single-logarithmic corrections to the small- $x$ flavor-singlet helicity evolution equations derived recently in the double-logarithmic approximation. The new single-logarithmic part of the evolution kernel sums up powers of $α_{s} ln (1/ x)$ , which are an important correction to the dominant powers of $α_{s} ln^{2} (1/ x)$ summed up by the double-logarithmic kernel at small values of Bjorken $x$ and with $α_{s}$ the strong coupling constant. The single-logarithmic terms arise separately from either the longitudinal or transverse momentum integrals. Consequently, the evolution equations we derive employing the light-cone perturbation theory simultaneously include the small- $x$ evolution kernel and the leading-order polarized DGLAP splitting functions. We further enhance the equations by calculating the running coupling corrections to the kernel.
↳ hep-phhep-exnucl-exnucl-thJHEP(2022)·53 citations
08
White dwarfs and generalized uncertainty principle
Idrus Husin Belfaqih🇮🇩 · Harris Maulana🇮🇩 · Anto Sulaksono🇮🇩
This work is motivated by the sign problem in a logarithmic parameter of black hole entropy and the existing more massive white dwarfs than the Chandrasekhar mass limit. We examine the quadratic, linear, and linear-quadratic generalized uncertainty principle (GUP) models within the virtue of recent masses and radii of white dwarfs. We consider the modification generated by introducing the minimal length proposal on the degenerate Fermi gas equation of state (EOS) and on the hydrostatic equation. For the latter, we applied Verlinde's proposal regarding entropic gravity to derived the quantum corrected Newtonian gravity which in turn responsible for modifying the hydrostatic equation. Through the chi-square analysis of the models, we have found that the observation data favor the quadratic dan linear GUP models without mass limit. However, for the quadratic-linear GUP model, we can obtain the positive value of the free parameter $γ_{0}$ as well as we can get mass limit more massive than the Chandrasekhar mass limit. In the linear-quadratic GUP model, the formation of stable massive white dwarfs than the Chandrasekhar limit is possible only if both parameters are not equal.
↳ gr-qcnucl-thInt.J.Mod.Phys.D(2021)·29 citations
09
Viscous control of minimum uncertainty state in hydrodynamics
T. Koide🇧🇷
A minimum uncertainty state for position and momentum of a fluid element is obtained. We consider a general fluid described by the Navier-Stokes-Korteweg (NSK) equation, which reproduces the behaviors of a standard viscous fluid, a fluid with the capillary action and a quantum fluid, with the proper choice of parameters. When the parameters of the NSK equation is adjusted to reproduce Madelung's hydrodynamic representation of the Schreodinger equation, the uncertainty relation of a fluid element reproduces the Kennard and the Robertson-Schreodinger inequalities in quantum mechanics. The derived minimum uncertainty state is the generalization of the coherent state and its uncertainty is given by a function of the shear viscosity. The viscous uncertainty can be smaller than the inviscid minimum value when the shear viscosity is smaller than a critical value which is similar in magnitude to the Kovtun-Son-Starinets (KSS) bound. This uncertainty reflects the information of the fluctuating microscopic degrees of freedom in the fluid and will modify the standard hydrodynamic scenario, for example, in heavy-ion collisions.
↳ quant-phhep-thnucl-thJ.Stat.Mech.(2022)·4 citations
10
Poisson bracket operator
T. Koide🇧🇷
We introduce the Poisson bracket operator which is an alternative quantum counterpart of the Poisson bracket. This operator is defined using the operator derivative formulated in quantum analysis and is equivalent to the Poisson bracket in the classical limit. Using this, we derive the quantum canonical equation which describes the time evolution of operators. In the standard applications of quantum mechanics, the quantum canonical equation is equivalent to the Heisenberg equation. At the same time, this equation is applicable to c-number canonical variables and then coincides with the canonical equation in classical mechanics. Therefore the Poisson bracket operator enables us to describe classical and quantum behaviors in a unified way. Moreover, the quantum canonical equation is applicable to non-standard system where the Heisenberg equation is not defined. As an example, we consider the application to the system where a c-number and a q-number particles coexist. The derived dynamics satisfies the Ehrenfest theorem and the energy and momentum conservations.
↳ quant-phhep-thnucl-thPRA(2021)·1 citation
11
The low energy inclusive $ν_{μ} (ν_{e}) -^{12}$ C scattering revisited
M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳
We have reviewed the current status of the inclusive neutrino scattering from $^{12}$ C in the low energy region corresponding to the neutrino beams from the pion, muon and kaon decaying at rest. The theoretical calculations of total cross sections in various nuclear models with special emphasis on the recent experiments with the monoenergetic neutrinos from KDAR [1] along with the older experiments from KARMEN and LSND collaborations have been discussed in the context of the recent works by Akbar et al. [2] and Nikolakopoulos et al. [3]. The inadequacy of the various theoretical models used to explain the experimental results on the inclusive neutrino scattering from nuclei at low energies has been highlighted and the need for a better understanding of the nuclear medium effects beyond the impulse approximation has been emphasized.
↳ hep-phnucl-th0 citations
12
Pion couplings with low-lying nucleon resonances
Janardan Prasad Singh🇮🇳
We have calculated coupling constants of a neutral pion with the lowest two nucleon resonances. This includes both the diagonal as well as non-diagonal coupling constants involving a nucleon resonance and a nucleon. For this, we first calculate vacuum-to-pion correlation function of the interpolating fields of two nucleons and then take its matrix elements with respect to a nucleon spinor and/or a nucleon resonance spinor(s). Using different QCD sum rules obtained from different matrix elements we eliminate unwanted coupling constants and solve for the desired ones. This is a simple extension of the projected correlation function approach used in the literature where we use multiple of states involving those of a nucleon and its resonances. We have also checked the stability of our results with respect to variation of different QCD and phenomenological input parameters.
↳ hep-phnucl-thNPA(2022)·1 citation
13
Computing the coefficients of transformations between oscillator states
V.D. Efros🇷🇺
A program is created to compute recursively the Moshinsky brackets. It is very fast and provides highly accurate results. In the case of the double-precision computations with a single-processor consumer notebook, the computing time per bracket at any not small oscillator excitations is on the scale of 10^{-8} s and the accuracy is very good for the total number of quanta up to 80. The program is easy to handle.
↳ physics.comp-phnucl-thComput.Phys.Commun.(2021)·7 citations
14
The multiple-charm hierarchy in the statistical hadronization model
Anton Andronic🇩🇪 · Peter Braun-Munzinger🇩🇪 · Markus K. Köhler🇩🇪 · Aleksas Mazeliauskas🇨🇭 · Krzysztof Redlich🇵🇱 · Johanna Stachel🇩🇪 · Vytautas Vislavicius🇩🇰
In relativistic nuclear collisions the production of hadrons with light (u,d,s) quarks is quantitatively described in the framework of the Statistical Hadronization Model (SHM). Charm quarks are dominantly produced in initial hard collisions but interact strongly in the hot fireball and thermalize. Therefore charmed hadrons can be incorporated into the SHM by treating charm quarks as 'impurities' with thermal distributions, while the total charm content of the fireball is fixed by the measured open charm cross section. We call this model SHMc and demonstrate that with SHMc the measured multiplicities of single charm hadrons in lead-lead collisions at LHC energies can be well described with the same thermal parameters as for (u,d,s) hadrons. Furthermore, transverse momentum distributions are computed in a blast-wave model, which includes the resonance decay kinematics. SHMc is extended to lighter collision systems down to oxygen-oxygen and includes doubly- and triply-charmed hadrons. We show predictions for production probabilities of such states exhibiting a characteristic and quite spectacular enhancement hierarchy.
↳ hep-phnucl-exnucl-thJHEP(2021)·132 citations

Affiliations

first authorsco-authorsvia INSPIRE