We construct regular black holes and horizonless spacetimes that are geodesically complete and satisfy the dominant energy condition from Einstein- Formula omitted gravities with several classes of ...analytic Formula omitted functions that can be viewed as perturbations to Maxwell's theory in weak field limit. We establish that regular black holes with special static metric ( Formula omitted) violate the strong energy condition and such a regular black hole with Minkowski core violates the null energy condition. We develop a formalism to perform electromagnetic duality transformations in Formula omitted. We obtain two new explicit examples where the duality is a symmetry. We study the properties of the corresponding dyonic black holes. We study the geodesic motions of a particular class of solutions that we call horizonless or black hole repulsons.
The decay width of the Formula omitted meson is dominated by the electromagnetic mode Formula omitted, and it is thus the longest-lived charged vector meson. In light of this point, we perform the ...first QCD LCSRs calculation of Formula omitted helicity form factors and discuss the experiment potential of discovering exclusive Formula omitted weak decays. The main result is the partial decay widths, which read as Formula omitted, Formula omitted, Formula omitted and Formula omitted. We show that these channels are promising in the near future, serving as the first experimental observation of weak decays of a vector meson, and would open up a new playground for precision test of the standard model.
The current knowledge on the Formula omitted meson are very limited. Besides the dominant electromagnetic decays, the Formula omitted weak decays are legal and offer the valuable opportunities to ...explore the wanted Formula omitted meson. In this paper, the Formula omitted decay was studied with the factorization approach. It is found that the branching ratio Formula omitted Formula omitted Formula omitted, which corresponds to several thousands of events at the Formula omitted collider experiments including STCF, SuperKEKB, CEPC and FCC-ee, and several millions of events at the hadron collider experiments, such as LHCb@HL-LHC. It is feasible to experimentally study the Formula omitted weak decay in the future, even considering the identification efficiency.
Under the aegis of isospin conservation, the amplitudes in Born approximation, i.e., considering the only one-photon-exchange mechanism, of the decay Formula omitted, where Formula omitted is a ...vector charmonium, and of the reaction Formula omitted at the Formula omitted mass, are parametrized by the same electromagnetic coupling. It follows that, the modulus of such a coupling can be extracted from the data on the two observables: the decay branching fraction and the annihilation cross section. By considering the first two vector charmonia, Formula omitted and Formula omitted, it is found that, especially in the case of Formula omitted, there is a substantial discrepancy between the values of the modulus of the same electromagnetic coupling extracted from the branching ratio and the cross section. We propose, as a possible explanation for such a disagreement, the presence in the decay amplitude of isospin-violating contributions driven by two different mechanisms, that, however, appear to be more favored in the Formula omitted than in the Formula omitted decays.
We study the contributions for the Formula omitted and Formula omitted originating from the intermediate states Formula omitted and Formula omitted in the charmless three-body decays Formula omitted, ...with Formula omitted, in the perturbative QCD approach. The subprocesses Formula omitted are introduced into the distribution amplitudes of Formula omitted system via the kaon electromagnetic form factors with the coefficients taken from the fitted results. The predictions of the branching fractions for the decays Formula omitted with the intermediate state Formula omitted decays into Formula omitted or Formula omitted are about Formula omitted of the corresponding results for the quasi-two-body decays Formula omitted in this work.
Microwave absorption materials are of great importance in various application nowadays. In this article, a new type of metal-organic framework (MOF)-based Fe/C@Co.sub.3O.sub.4 core-shell ...nanocomposites is introduced for microwave absorption coating applications, via a simple and low-cost fabrication process. The nanocomposites have been successfully synthesized via a controlled high-temperature treatment of a PB@Co(OH).sub.2 precursor, which was prepared earlier by a solvent-thermal method. The nanocomposites have excellent microwave absorption properties, and the maximum reflection loss (RL) value and effective bandwidth (RL < - 10 dB) can be tuned by the fabrication parameters. The results show that the different nanostructures and electromagnetic properties of the Fe/C@Co.sub.3O.sub.4 nanocomposites can be obtained by the heat treatments with different temperatures. With an excellent attenuation performance and distinguished impedance matching properties, the nanocomposite processed by a heat treatment at 700 °C (ICCO-700) has the best microwave absorption results. The maximum RL value reaches - 58.5 dB at 4.57 GHz, which is a remarkable valley in the low frequency range, when the absorber thickness is 2.5 mm. The effective bandwidth can be as wide as 11.0 GHz, when the sample thickness is 5.0 mm, which covers three quarters of the S band, one half of the C band, one half of the X band and the whole Ku band.
We perform a calculation of the mass distribution in the Formula omitted decay, studying both the Formula omitted and Formula omitted decays. The electromagnetic interaction is such that the tree ...level amplitude is null for the neutral channel, which forces the Formula omitted transition to go through a loop involving the Formula omitted scattering amplitude. We take the results for this amplitude from a theoretical model that predicts a Formula omitted bound state and find a Formula omitted mass distribution in the decay drastically different than phase space. The rates obtained are relatively large and the experiment is easily feasible in the present BESIII facility. The performance of this experiment could provide an answer to the issue of this much searched for state, which is the analogue of the Formula omitted resonance.
The heavy baryon system bounded by the strong interaction has a rich internal structure, so its mass spectra can have the fine structure similar to the line spectra of atom bounded by the ...electromagnetic interaction. We systematically study the internal structure of P-wave Formula omitted baryons and calculate their D-wave decay properties. The present study, together with our previous studies on their mass spectra and S-wave decay properties, suggest that all the four excited Formula omitted baryons recently discovered by LHCb can be well explained as P-wave Formula omitted baryons, and their beautiful fine structure is directly related to the rich internal structure of P-wave Formula omitted baryons.
Electromagnetic form factors serve to explore the intrinsic structure of nucleons and their strangeness partners. With electron scattering at low energies the electromagnetic moments and radii of ...nucleons can be deduced. The corresponding experiments for hyperons are limited because of the unstable nature of the hyperons. Only for one process this turns to an advantage: the decay of the neutral Sigma hyperon to a Lambda hyperon and a real or virtual photon. Due to limited phase space the effects caused by the Sigma-to-Lambda transition form factors compete with the QED radiative corrections for the decay Formula omitted. These QED corrections are addressed in the present work, evaluated beyond the soft-photon approximation, i.e., over the whole range of the Dalitz plot and with no restrictions on the energy of the radiative photon.
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