New accurate data for the spectrum of neutral silver

High resolution spectra of neutral silver have been recorded by Fourier Transform Spectrometry in the region 2 000-8 280 ?(50 000-12 000 cm^-1) with silver-neon and silver-argon hollow cathode lamps as sources. This work represents order-of-magnitude improvements, compared to previous work on Ag I, in accuracy of transition wavelengths and wavenumbers, and energy level values. 35 classified Ag I transitions are given, and the wavenumber uncertainty for the strongest lines is less than 0.002 cm^-1. Improved values for 28 energy levels are presented. Received 31 January 2000 and Received in final form 13 June 2000     

Radiative transitions in highly ionised silicon-like ions

Transition energies, oscillator strengths and transition probability values for radiative transitions have been calculated for the highly ionised atoms of Si isoelectronic sequence from Mn¹¹⁺ to Kr²²⁺ for the singly excited states up to principal quantum number n = 7. Time-dependent coupled Hartree-Fock (TDCHF) theory has been used to estimate such transition properties. Most of the results for the oscillator strengths and transition probabilities are new. Transition energies agree reasonably well with available spectroscopic values. Received 25 January 2000 and Received in final form 24 October 2000     

Experimental and theoretical lifetimes in Yb III

Lifetimes of three levels belonging to the configuration 4f ¹³5d with J = 1 in Yb III have been measured for the first time using the time-resolved laser-induced fluorescence method. Experimental transition probabilities have been deduced for the transitions between the levels studied and the ground state. The comparison of the experimental lifetimes with theoretical data, deduced within the relativistic Hartree-Fock (HFR) approach, underlines the dramatic importance of an adequate consideration of core-polarization effects in the theoretical model and the sensitivity of one of the lifetime values to small correlation effects. Received 2 April 2001     

Imperfect bifurcation of systems with slowly varying parameters and application to Duffing's equation

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎＰｈｙｓｉｃｓ,Ｍｅｃｈａｎｉｃｓ,ＣｈｅｍｉｓｔｒｙａｎｄＬｉｆｅＳｃｉｅｎｃｅｅｔｃ.,ｔｈｅｒｅｅｘｉｓｔｓｔｈｅｆｏｌｌｏｗｉｎｇｂｉｆｕｒｃａｔｉｏｎｐｒｏｂｌｅｍｗｉｔｈａｐａｒａｍｅｔｅｒ ｘ=ｆ(ｘ ,λ)　　 (ｘ∈Ｒｎ,λ∈Ｒ) ,(1 )ｗｈｅｒｅλｉｓａｃｏｎｔｒｏｌｌｉｎｇｐａｒａｍｅｔｅｒｏｆｂｉｆｕｒｃａｔｉｏｎａｎｄｆ(ｘ ,λ) ∈Ｒｎｉｓａｎｎ＿ｄｉｍｅｎｓｉｏｎａｌｖｅｃｔｏｒｆｉｅｌｄ .Ｔｈｅｂｉｆｕｒｃａｔｉｏｎｐｒｏｂｌｅｍｗｉｔｈａｃｏｎｓｔａｎ…     

基于转捩SST模型凸起圆柱绕流数值研究

为了研究局部凸起对边界层转捩的影响,采用转捩SST模型分别对亚临界、临界和超临界状态下带突起的圆柱绕流问题进行了数值模拟,分析了不同Reynolds数下带突起的圆柱绕流问题的近壁面流动特征以及表面时均压力与摩擦力系数的分布和凸起对圆柱表面流动分离以及转捩的影响,对比了有无凸起两侧圆柱表面时均压力、摩擦力系数的不同. 结果表明:当来流Reynolds数处于临界区时,气流在圆柱上表面凸起处形成了3个反向旋转的漩涡,之后随着θ的增大,发生了流动分离和流动转捩现象;对于不同Reynolds数下的来流,圆柱上表面的凸起可以使气流发生转捩的位置提前;圆柱上表面的凸起使流速增大、压强降低,从而导致圆柱产生升力,随着来流Reynolds数的增大,其升力逐渐变大.      

Dynamical properties of the Haldane chain with bond disorder

By using Lanczos exact diagonalization and quantum Monte Carlo combined with stochastic analytic continuation, we study the dynamical properties of the S = 1 antiferromagnetic Heisenberg chain with different strengths of bond disorder. In the weak disorder region, we find weakly coupled bonds which can induce additional low-energy excitation below the one-magnon mode. As the disorder increases, the average Haldane gap closes at δ_∆ ~ 0.5 with more and more low-energy excitations coming out. After the critical disorder strength δ_c ~ 1, the system reaches a random-singlet phase with prominent sharp peak at ω = 0 and broad continuum at ω > 0 of the dynamic spin structure factor. In addition, we analyze the distribution of random spin domains and numerically find three kinds of domains hosting effective spin-1/2 quanta or spin-1 sites in between. These “spins” can form the weakly coupled longrange singlets due to quantum fluctuation which contribute to the sharp peak at ω = 0.     

The microstructure and Ruppeiner geometry of charged anti-de Sitter black holes in Gauss–Bonnet gravity: from the critical point to the triple point

Ruppeiner geometry has been successfully applied in the study of the black hole microstructure by combining with the small–large black hole phase transition, and the potential interactions among the molecular-like constituent degrees of freedom are uncovered. In this paper, we will extend the study to the triple point, where three black hole phases coexist acting as a typical feature of black hole systems quite different from the small–large black hole phase transition. For the six-dimensional charged Gauss–Bonnet anti-de Sitter black hole, we thoroughly investigate the swallow tail behaviors of the Gibbs free energy and the equal area laws. After obtaining the black hole triple point in a complete parameter space, we exhibit its phase structures both in the pressure–temperature and temperature–horizon radius diagrams. Quite different from the liquid–vapor phase transition, a double peak behavior is present in the temperature–horizon radius phase diagram. Then we construct the Ruppeiner geometry and calculate the corresponding normalized curvature scalar. Near the triple point, we observe multiple negatively divergent behaviors. Positive curvature scalar is observed for the small black hole with high temperature, which indicates that the repulsive interaction dominates among the microstructure. Furthermore, we consider the variation of the curvature scalar along the coexisting intermediate and large black hole curves. Combining with the observation for different fluids, the result suggests that this black hole system behaves more like the argon or methane. Our study provides a first and preliminary step towards understanding black hole microstructure near the triple point, as well as uncovering the particular properties of the Gauss–Bonnet gravity.     

Most probable transition paths in eutrophicated lake ecosystem under Gaussian white noise and periodic force

The effects of stochastic perturbations and periodic excitations on the eutrophicated lake ecosystem are explored. Unlike the existing work in detecting early warning signals, this paper presents the most probable transition paths to characterize the regime shifts. The most probable transition paths are obtained by minimizing the Freidlin-Wentzell (FW) action functional and Onsager-Machlup (OM) action functional, respectively. The most probable path shows the movement trend of the lake eutrophication system under noise excitation, and describes the global transition behavior of the system. Under the excitation of Gaussian noise, the results show that the stability of the eutrophic state and the oligotrophic state has different results from two perspectives of potential well and the most probable transition paths. Under the excitation of Gaussian white noise and periodic force, we find that the transition occurs near the nearest distance between the stable periodic solution and the unstable periodic solution.     

Majorana zero modes,unconventional real-complex transition,and mobility edges in a one-dimensional non-Hermitian quasi-periodic lattice

A one-dimensional non-Hermitian quasiperiodic p-wave superconductor without PT-symmetry is studied.By analyzing the spectrum,we discovered that there still exists real-complex energy transition even if the inexistence of PT-symmetry breaking.By the inverse participation ratio,we constructed such a correspondence that pure real energies correspond to the extended states and complex energies correspond to the localized states,and this correspondence is precise and effective to detect the mobility edges.After investigating the topological properties,we arrived at a fact that the Majorana zero modes in this system are immune to the non-Hermiticity.     

Quantum phase transitions in CePdAl probed by ultrasonic and thermoelectric measurements

CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressure- or field-tuned, extended quantum critical phase at zero temperature. Identifying characteristic signatures of the emerging quantum critical phase, which are expected to be distinct from those near a quantum critical point, remains challenging. In this work, by performing ultrasonic and thermoelectric measurements down to very low temperatures in a ³He-⁴He dilution refrigerator in the presence of magnetic field, we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase, including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.