Nuclear Theory·nucl-th

Monday·January 10, 2022

8 papers—4 primary·4 cross-listed

01
Coherence dynamics in low-energy nuclear fusion
Iain Lee🇬🇧 · Alexis Diaz-Torres🇬🇧
Low-energy nuclear fusion reactions have been described using a dynamical coupled-channels density matrix method, based on the theory of open quantum systems. For the first time, this has been combined with an energy projection method, permitting the calculation of energy resolved fusion probabilities. The results are benchmarked against calculations using stationary Schrödinger dynamics and show excellent agreement. Calculations of entropy, energy dissipation and coherence were conducted, demonstrating the capability of this method. It is evident that the presence of quantum decoherence does not affect fusion probability. This framework provides a basis for quantum thermodynamic studies using thermal environments.
nucl-thnucl-exquant-phPLB(2022)·10 citations
02
Information content of the differences in the charge radii of mirror nuclei
Paul-Gerhard Reinhard · Witold Nazarewicz
Differences in the charge radii of mirror nuclei have been recently suggested to contain information on the slope of the symmetry energy L. To test this hypothesis, we perform statistical correlation analysis using quantified energy density functionals that are consistent with our previous knowledge on global nuclear observables such as binding energies and charge radii. We conclude that the difference in charge radii between a mirror pair, R_mir, is an inferior isovector indicator compared to other observables, such at the neutron skin or electric dipole polarizability. In particular, this quantity correlates poorly with both the neutron skin and L. We demonstrate that R_mir is influenced by pairing correlations in the presence of low-lying proton continuum in the proton-rich mirror-partner nucleus. Considering the large theoretical uncertainties on R_mir, we conclude that the precise data on mirror charge radii cannot provide a stringent constraint on L.
nucl-thPRC(2022)·44 citations
03
Practical considerations for the effect of finite coverage on the azimuthal dependence of global spin alignment
Chao Zhang🇨🇳 · Peng Yang🇨🇳 · Feng Liu🇨🇳 · Biao Tu🇨🇳
The global spin alignment of vector mesons is a powerful probe to study the vorticity field of the system produced in non-central relativistic heavy-ion collisions. Since the experimental observables of global spin alignment are sensitive to many factors, proper corrections are need to be taken care of when measuring the global spin alignment of vector mesons. In this paper, we propose a method to correct the effect of finite pseudo-rapidity coverage when extract the azimuthal dependence of spin alignment parameter $ρ_{00}$ . The effects of the finite pseudo-rapidity coverage on the azimuthal dependence of $ϕ$ meson spin alignment and the potentially exist intrinsic spin alignment effects are taken into consideration. The method presented in this paper is verified in a Monte-Carlo simulation, it allows the measurements of azimuthal dependence of global spin alignment to be conducted properly and accurately.
nucl-thnucl-exPRC(2022)·0 citations
04
Characterization of the inner edge of the neutron star crust
R. Shafieepour · H.R. Moshfegh · J. Piekarewicz
The poorly known crustal equation of state plays a critical role in many observational phenomena associated with a neutron star. Using semi-classical Monte Carlo simulations, we explore the possible configurations of the inner edge of the neutron-star crust for a variety of baryon densities and proton fractions. Applying the Kirkwood--Buff theory to these two-component systems, we observe how the isothermal compressibility reaches a maximum when isolated non-symmetric clusters are formed in an extremely dilute neutron gas. To determine the neutron fraction, we suggest a geometrical model based on the behavior of the proton-neutron pair correlation function. Accordingly, the equation of state of the inner crust is calculated, illustrating that the nuclear energy in beta-equilibrium follows a power-law behavior with baryon density. As a possible astrophysical outcome of this study, our results could help refine the mass-radius relation. Finally, our results pave the way towards further investigations of the impact of the proton-neutron pair correlation function on transport properties within the neutron-star crust.
nucl-thPRC(2022)·3 citations
05
Topological confinement in Skyrme holography
Casey Cartwright🇺🇸 · Benjamin Harms🇺🇸 · Matthias Kaminski🇺🇸 · Ronny Thomale🇩🇪
We study phase transitions in five-dimensional Einstein Gravity with a negative cosmological constant, coupled to a Skyrme matter field. These transitions are topological generalizations of the Hawking-Page transition between thermal Anti de Sitter (AdS) spacetime and an AdS black hole. Phases are characterized by a topological number associated with the Skyrme field configuration. Depending on that topological number and on the Skyrme coupling strength, there occur transitions between those phases at two, one, or no value(s) of the temperature. Through the holographic (AdS/CFT) correspondence, these solutions are dual to topologically non-trivial states in a conformal field theory (CFT) with an SU(2)-symmetry, which support either confined or deconfined (quasi-)particles at strong coupling. We compare to similar known phase transitions, and discuss potential applications to confinement in topological phases of condensed matter and the quark-gluon plasma.
↳ hep-thcond-mat.str-elhep-phnucl-thClass.Quant.Grav.(2022)·3 citations
06
Chiral condensates and screening masses of neutral pseudoscalar mesons in thermomagnetic QCD medium
H.-T. Ding🇨🇳 · S.-T. Li🇨🇳 · J.-H. Liu🇨🇳 · X.-D. Wang🇨🇳
We point out that chiral condensates at nonzero temperature and magnetic fields are in strict connection to the space-time integral of corresponding two-point neutral meson correlation functions in the pseudoscalar channel via the Ward-Takahashi identity. Screening masses of neutral pseudoscalar mesons, which are defined as the exponential decay of the corresponding spatial correlation functions in the long distance, thus are intrinsically connected to (inverse) magnetic catalysis of chiral condensates. To study this we performed lattice simulations of $(2 + 1)$ -flavor QCD on $3 2^{3} \times N_{t}$ lattices with pion mass $M_{π} ≃ 220$ MeV in a fixed scale approach having temperature $T \in [17, 281]$ MeV and magnetic field strength $e B \in [0, 2.5]$ GeV $^{2}$ . We find that screening lengths, i.e. inverses of screening masses of $π^{0}$ , $K^{0}$ and $η_{s s ˉ}^{0}$ , turn out to have the similar complex $e B$ and $T$ dependences of the corresponding chiral condensates. Although the transition temperature is found to always decrease as $e B$ grows, we show that the suppression due to magnetic fields becomes less significant for hadron screening length and chiral condensates with heavier quarks involved, and ceases to occur for $η_{s s ˉ}^{0}$ and strange quark chiral condensate. The complex $e B$ and $T$ dependences of both screening masses and chiral condensates, reflecting the crossover nature of the QCD transition, are attributed to the competition between sea and valence quark effects. These findings could be useful to guide low-energy models and effective theories of QCD.
↳ hep-lathep-phhep-thnucl-thPRD(2022)·54 citations
07
Rethinking the ill-posedness of the spectral function reconstruction -- why is it fundamentally hard and how Artificial Neural Networks can help
Shuzhe Shi🇨🇦 · Lingxiao Wang🇩🇪 · Kai Zhou🇩🇪
Reconstructing hadron spectral functions through Euclidean correlation functions are of the important missions in lattice QCD calculations. However, in a Källen--Lehmann(KL) spectral representation, the reconstruction is observed to be ill-posed in practice. It is usually ascribed to the fewer observation points compared to the number of points in the spectral function. In this paper, by solving the eigenvalue problem of continuous KL convolution, we show analytically that the ill-posedness of the inversion is fundamental and it exists even for continuous correlation functions. We discussed how to introduce regulators to alleviate the predicament, in which include the Artificial Neural Networks(ANNs) representations recently proposed by the Authors in~[Phys. Rev. D 106 (2022) L051502]. The uniqueness of solutions using ANNs representations is manifested analytically and validated numerically. Reconstructed spectral functions using different regularization schemes are also demonstrated, together with their eigen-mode decomposition. We observe that components with large eigenvalues can be reliably reconstructed by all methods, whereas those with low eigenvalues need to be constrained by regulators.
↳ hep-phhep-latmath-phmath.MP+1Comput.Phys.Commun.(2023)·37 citations
08
On the definition of local spatial densities in hadrons
E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · N. Lange🇩🇪 · U.-G. Meißner🇩🇪 · M. V. Polyakov🇩🇪
We show that the matrix element of a local operator between hadronic states gives rise to an unambiguous definition of the associated spatial density. As an explicit example, we consider the charge density of a spinless particle in the rest and moving frames and clarify its relationship to the electric form factor. Our results suggest that the interpretation of the spatial densities of local operators and their moments such as the mean square charge radius needs to be revised.
↳ hep-phhep-exnucl-thPRL(2022)·67 citations

Affiliations

first authorsco-authorsvia INSPIRE