We analyze 4050 wide binary star systems involving a white dwarf (WD) and usually a main-sequence (MS) star, drawn from the large sample assembled by Tian et al. Using the modeling code BASE-9, we determine the system’s ages, the WD progenitors’ zero-age MS masses, the extinction values (A V ), and the distance moduli. Discarding the cases with poor age convergences, we obtain ages for 3551 WDs, with a median age precision of σ τ /τ = 20%, and system ages typically in the range of 1–6 Gyr. We validated these ages against the very few known clusters and through cross validation of 236 WD-WD binaries. Under the assumption that the components are coeval in a binary system, this provides precise age constraints on the usually low-mass MS companions, mostly inaccessible by any other means.
Based on the first principle method, the structural and electronic properties for two-dimensional (2D) Au2B are studied. Our investigations indicate 2D Au2B has the similar crystal structure to 2D transition metal dichalcogenides (TMDs). Electronic structures show 2D Au2B is a typical non-magnetic metal. Native defects (Au and B vacancy), strains and functional groups (F and Cl absorbed cases) could not destroy its metallic characters. Stable metallic properties suggest 2D Au2B is an alternative and promising electrode material for 2D heterogeneous junctions based on the TMDs. For the Li absorbed case, large negative adsorption energies imply the strong interactions between Li and 2D Au2B, which means 2D Au2B, when utilized as the Li-ion batteries anodes, could prevent the formation of metallic Li and improve the Li-ion batteries' safety and reversibility.
Communities are ubiquitous in nature and society. Individuals that share common properties often self-organize to form communities. Being able to identify community structure could help us understand and explore complex systems efficiently. Avoiding the shortages of computation complexity, pre-given information and unstable results in different run, in this paper, we propose one simple and efficient method to try to give a deep understanding of the emergence and diversity of communities in complex systems. By introducing rational random selection, our method reveals the hidden deterministic and normal diverse community states of community structure. To demonstrate this method, we test it with real-world systems. The results show that our method could not only detect community structure with high sensitivity and reliability, but also could provide instructional information about our normal diverse community world and the hidden deterministic community world by giving out the core-community, the real-community, the tide (boundary) and the diversity. This is of paramount importance in understanding, predicting, and controlling a variety of collective behaviors in complex systems.
The transfer of optical vortices is studied based on double two-photon processes in a four-level diamond configuration system. A pair of strong fields are applied to prepare atomic coherence, while two weak probe fields are coupled with the other two transitions. When the two-photon resonances are satisfied, the analytical results for the intensities of the probe fields are calculated using perturbation theory and an adiabatic approximation approach. Our results explore whether the orbital angular momentum of an input probe beam or the second control field can be transferred to the generated probe field, and this is verified by numerical simulation. It is interesting that as the intensities of the control fields increase, the propagation of probe beams exhibits oscillation behaviors only when the one-photon detuning is nonzero. Furthermore, we show that the absorption losses are minimized, and the transfer efficiency is enhanced by appropriately modifying the one-photon detuning together with the control-field Rabi frequencies.
We propose a scheme to generate quadripartite Greenberger-Horne-Zeilinger entanglement by coherently preparing the five-level K-type atoms in a superposition initially. The conditions of initial atomic populations and atomic coherences to obtain the output genuine quadripartite entanglement are analyzed numerically in detail. It is found that good entanglement occurs when populations of the bottom levels are much more than the upper levels, or vice versa. In addition, the dependence of quantum entanglement on linear gain coefficient, cavity damping constant, and thermal fluctuation effect are also discussed. Our numerical results confirm that the quadripartite entanglement can be realized by choosing proper values of the initial atomic population, which provide convenience for experimental implementation.
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