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In this work we study the properties of quarkonium states in a quark-gluon plasma which, due to expansion and non-zero viscosity, exhibits a local anisotropy in momentum space. We determine the hard-loop resummed gluon propagator in an anisotropic QCD plasma in general linear gauges and define a potential between heavy quarks from the Fourier transform of its static limit. This potential which arises due to one-gluon exchange describes the force between a quark and anti-quark at short distances. It is closer to the vacuum potential as compared to the isotropic Debye screened potential which indicates the reduced screening in an anisotropic QCD plasma. In addition, angular dependence appears in the potential; we find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment. The potential at long distances, however, is non-perturbative and modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is non-zero and inversely proportional to the temperature. With a phenomenological potential model which incorporates the different behaviors at short and long distances, we solve the three-dimensional SchrÃ¶dinger equation. Our numerical results show that quarkonium binding is stronger at non-vanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states. Furthermore, we determine viscosity corrections to the imaginary part of the heavyquark potential in the weak-coupling hard-loop approximation. The imaginary part is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma.

We determine the hard-loop resummed propagator in an anisotropic QCD plasma in general covariant gauges and define a potential between heavy quarks from the Fourier transform of its static limit. We find that there is stronger attraction on distance scales on the order of the inverse Debye mass for quark pairs aligned along the direction of anisotropy than for transverse alignment.

New species of genus Atractides Koch, 1837 (Acari: Hydrachnidiae, Hygrobatidae) from Qinghai, China
(2022)

The paper deals with five new species of the genus Atractides Koch, 1837 (Acari: Hydrachnidiae, Hygrobatidae) collected from Qinghai Province, P.R. China, Atractides (Atractides) biprojectus Zhang, Li & Guo sp. nov., Atractides (Atractides) smiti Zhang, Li & Guo sp. nov., Atractides (Atractides) menyuanensis Zhang, Li & Guo sp. nov., Atractides (Atractides) longiprojectus Zhang, Li & Guo sp. nov. and Atractides (Atractides) xianmiensis Zhang, Li & Guo sp. nov. All the new species are described and illustrated in detail, and all the type specimens are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (GUGC).