Relativistic symmetry breaking in light kaonic nuclei

As the experimental data from kaonic atoms and $K^{-}N$ scatterings imply that the $K^{-}$-nucleon interaction is strongly attractive at saturation density, there is a possibility to form $K^{-}$-nuclear bound states or kaonic nuclei. In this work, we investigate the ground-state properties of the light kaonic nuclei with the relativistic mean field theory. It is found that the strong attraction between $K^{-}$ and nucleons reshapes the scalar and vector meson fields, leading to the remarkable enhancement of the nuclear density in the interior of light kaonic nuclei and the manifest shift of the single-nucleon energy spectra and magic numbers therein. As a consequence, the pseudospin symmetry is shown to be violated together with enlarged spin-orbit splittings in these kaonic nuclei.Comment: 15 pages, 7 figure

An interpretable machine-learned model for international oil trade network

Energy security and energy trade are the cornerstones of global economic and social development. The structural robustness of the international oil trade network (iOTN) plays an important role in the global economy. We integrate the machine learning optimization algorithm, game theory, and utility theory for learning an oil trade decision-making model which contains the benefit endowment and cost endowment of economies in international oil trades. We have reconstructed the network degree, clustering coefficient, and closeness of the iOTN well to verify the effectiveness of the model. In the end, policy simulations based on game theory and agent-based model are carried out in a more realistic environment. We find that the export-oriented economies are more vulnerable to be affected than import-oriented economies after receiving external shocks. Moreover, the impact of the increase and decrease of trade friction costs on the international oil trade is asymmetrical and there are significant differences between international organizations.Comment: 14 pages, 5 figure

Strong correlation of the neutron star core-crust transition density with the σ\sigma-meson mass via vacuum polarization

We study the neutron star core-crust transition density $\rho_t$ with the inclusion of the vacuum polarization in the dielectric function in the nonlinear relativistic Hartree approach (RHAn). It is found that the strong correlation between the $\rho_{t}$ and the scalar meson mass $m_{\sigma}$ strikingly overwhelms the uncertainty of the nuclear equation of state in the RHAn models, in contrast to the usual awareness that $\rho_{t}$ is predominantly sensitive to the isovector nuclear potential and symmetry energy. The accurate extraction of $\rho_{t}$ through the future gravitational wave measurements can thus provide a strong constraint on the longstanding uncertainty of $m_{\sigma}$, which is of significance to better infer the vacuum property. As an astrophysical implication, it suggests that the correlation between $\rho_t$ and $m_\sigma$ is very favorable to reconcile the difficulty in reproducing the large crustal moment of inertia for the pulsar glitches with the well constrained symmetry energy.Comment: 11 pages, 4 figure

Should gold be stored in chaotic eras?

This article explores the necessity to store gold in chaotic eras from the perspective of geopolitical risk (G.P.R.). We examine the casual relationship between G.P.R. and gold price (G.P.) by applying the full- and sub-sample rolling-window bootstrap causality test. The positive effect from G.P.R. to G.P. reveals that gold should be stored in chaotic eras, due to its rising price during high risks of geopolitics. However, the negative effect does not confirm this view, G.P. may decrease during certain high G.P.R. periods, which are not necessary to store gold. G.P. may also increase during periods of low G.P.R., in order to hedge risks of economic crises, rather than geopolitical events. These results are inconsistent with the capital asset pricing model, which highlights a positive effect from G.P.R. to G.P. In turn, the positive influence of G.P. on G.P.R. points out that the gold market can be an effective predictor of the risks of geopolitics. In the context of an unstable pattern of global politics, investors and governments can benefit from the gold value in the chaotic eras to avoid losses and optimize investment. In turn, they can accurately predict G.P.R. based on G.P., in order to prevent G.P.R.s