(2+1)(2+1)-dimensional regular black holes with nonlinear electrodynamics sources

On the basis of two requirements: the avoidance of the curvature singularity and the Maxwell theory as the weak field limit of the nonlinear electrodynamics, we find two restricted conditions on the metric function of $(2+1)$-dimensional regular black hole in general relativity coupled with nonlinear electrodynamics sources. By the use of the two conditions, we obtain a general approach to construct $(2+1)$-dimensional regular black holes. In this manner, we construct four $(2+1)$-dimensional regular black holes as examples. We also study the thermodynamic properties of the regular black holes and verify the first law of black hole thermodynamics.Comment: 13 pages, 4 figures. in press in PL

Momentum-dependence of ρ−ω\rho-\omega mixing in the pion vector form factor and its effect on (g−2)μ(g-2)_\mu

The inclusion of the $\rho-\omega$ mixing effect is crucial for a good description of the pion electromagnetic form factor in the $e^+e^- \rightarrow \pi^+\pi^-$ process, which quantifies the two-pion contribution to the anomalous magnetic moment of the muon $a_\mu$. In this paper, we try to analyze the impact of the momentum-dependence of the $\rho-\omega$ mixing within the framework of resonance chiral theory. The momentum-dependence of the $\rho-\omega$ mixing is incorporated due to the calculation of loop contributions at the next-to-leading order in the $1/N_C$ expansion. The work of {[}Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69 (2018) 1{]} is revisited taking into account the contribution due to the kaon mass splitting in the kaon loops and the latest experimental data. We perform two kinds of fits (with momentum-independent or momentum-dependent $\rho-\omega$ mixing amplitude) describing the $e^+e^-\rightarrow \pi^+\pi^-$ and $\tau\rightarrow \nu_{\tau}2\pi$ data in the energy region of 600$\sim$900 MeV and the decay width of $\omega \rightarrow \pi^+\pi^-$, and compare their results. It is found that taking account of the momentum-dependence of $\rho-\omega$ mixing can describe the pion vector form factor data a little better. For the contribution to the anomalous magnetic moment of the muon $a_\mu^{\pi\pi}|_{[0.6,0.9]\text{GeV}}$, the values of the results in the fits considering the momentum-dependent $\rho-\omega$ mixing amplitude are agree well with those in the fits without including the momentum-dependence of the $\rho-\omega$ mixing within errors. In addition, based on the fitted values of the involved parameters, we find that in the decay width of $\omega \rightarrow \pi^+\pi^-$ the contribution from the direct $\omega_I\pi\pi$ coupling is comparable with the contribution due to the $\rho-\omega$ mixing.Comment: 21 pages, 4 figures. arXiv admin note: text overlap with arXiv:1710.1144