Anomalous Light Scattering by Topological PT{\mathcal{PT}}-symmetric Particle Arrays

Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian $\mathcal{PT}$-symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a $\mathcal{PT}$-symmetric unit is inserted into the communication channel.Comment: 16 pages, 8 figure

Demonstrating Additional Law of Relativistic Velocities based on Squeezed Light

Special relativity is foundation of many branches of modern physics, of which theoretical results are far beyond our daily experience and hard to realized in kinematic experiments. However, its outcomes could be demonstrated by making use of convenient substitute, i.e. squeezed light in present paper. Squeezed light is very important in the field of quantum optics and the corresponding transformation can be regarded as the coherent state of SU(1; 1). In this paper, the connection between the squeezed operator and Lorentz boost is built under certain conditions. Furthermore, the additional law of relativistic velocities and the angle of Wigner rotation are deduced as well

Variational formulas of higher order mean curvatures

In this paper, we establish the first variational formula and its Euler-Lagrange equation for the total $2p$-th mean curvature functional $\mathcal {M}_{2p}$ of a submanifold $M^n$ in a general Riemannian manifold $N^{n+m}$ for $p=0,1,...,[\frac{n}{2}]$. As an example, we prove that closed complex submanifolds in complex projective spaces are critical points of the functional $\mathcal {M}_{2p}$, called relatively $2p$-minimal submanifolds, for all $p$. At last, we discuss the relations between relatively $2p$-minimal submanifolds and austere submanifolds in real space forms, as well as a special variational problem.Comment: 13 pages, to appear in SCIENCE CHINA Mathematics 201

Measurement of muon intensity by Cerenkov method

Optical detection is an important technique in studies and observations of air showers, muons and relevant phenomena. The muon intensity is measured in a proper energy range and to study some problems about Cerenkov radiation of cosmic rays are studied, by a muon-telescope operated with Cerenkov detector. It is found that the measured muon intensity agrees with the integral energy spectrum of cosmic ray muons

Extracting the phase information from atomic memory by intensity correlation measurement

We demonstrate experimentally controlled storage and retrieval of the optical phase information in a higher-order interference scheme based on Raman process in 87Rb atomic vapor cells. An interference pattern is observed in intensity correlation measurement between the write Stokes field and the delayed read Stokes field as the phase of the Raman write field is scanned. This result implies that the phase information of the Raman write field can be written into the atomic spin wave via Raman process in a high gain regime and subsequently read out via a spin-wave enhanced Raman process, thus achieving optical storage of phase information. This technique should find applications in optical phase image storage, holography and information processing

Mesenchymal stem cells and immunomodulation: current status and future prospects

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Measurement of the local density spectrum

Since there is still disagreement among the results of various groups, a measurement of the local density spectrum with a close-packed array of four scintillators, each of area 0.14 sq cm was made. Data are taken with conventional electronics, supervised by an on-line microcomputer. The data are stored on audio cassettes and analyzed with the aid of another microcomputer. Since four independent samples for each shower are available, uncertainties inherent in results from many earlier experiments can be minimized

Effect of oxygen surfactant on the magnetic and structural properties of Co films grown on Cu(110)

ABSTRACT It was found that atomically flat Co(110) films could be grown on Cu(110) using O as a surfactant. To obtain detailed knowledge on the effect of O on the growth, as well as on the magnetic properties of Co overlayer, we carried out an investigation on this system using Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED), Surface Magneto-Optic Kerr Effect (SMOKE), and Scanning Tunneling Microscopy (STM). With O as a surfactant, the initial growth of Co (<1 ML) results in a flat monolayer structure. When the Co is thicker than 1 ML, three-dimensional clusters begin to form. These clusters become ordered islands at 3 ML Co and coalesce at ~5 ML Co. Above 5 ML Co, layer-by-layer growth resumes. No significant Cu segregation is observed. SMOKE studies at room temperature show that the Co film is magnetic above ~5 ML Co, with the magnetization easy axis along the [001] direction. On the other hand, without using oxygen as a surfactant, Co grows three-dimensionally on Cu(110). The Co overlayer has its easy magnetization axis along the [001] direction, but the onset of the magnetization was observed at 11 ML Co at room temperature