Exact quantum dynamics of XXZ central spin problems

We obtain analytically close forms of benchmark quantum dynamics of the collapse and revival (CR), reduced density matrix, Von Neumann entropy, and fidelity for the XXZ central spin problem. These quantities characterize the quantum decoherence and entanglement of the system with few to many bath spins, and for a short to infinitely long time evolution. For the homogeneous central spin problem, the effective magnetic field $B$, coupling constant $A$ and longitudinal interaction $\Delta$ significantly influence the time scales of the quantum dynamics of the central spin and the bath, providing a tunable resource for quantum metrology. Under the resonance condition $B=\Delta=A$, the location of the $m$-th revival peak in time reaches a simple relation $t_{r} \simeq\frac{\pi N}{A} m$ for a large $N$. For $\Delta =0$, $N\to \infty$ and a small polarization in the initial spin coherent state, our analytical result for the CR recovers the known expression found in the Jaynes-Cummings model, thus building up an exact dynamical connection between the central spin problems and the light-matter interacting systems in quantum nonlinear optics. In addition, the CR dynamics is robust to a moderate inhomogeneity of the coupling amplitudes, while disappearing at strong inhomogeneity.Comment: added new result on inhomogeneous central spin problem and added new references and supplementary material, 6 pages + 15 pages; 4 figures + 14 figure

2,2,2-Trifluoro­ethyl 4-methyl­benzene­sulfonate

In the crystal structure of the title compound, C9H9F3O3S, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules along the c-axis direction. Also present are slipped π–π stacking inter­actions between phenyl­ene rings, with perpendicular inter­planar distances of 3.55 (2) Å and centroid–centroid distances of 3.851 (2) Å

Methyl 2-amino-5-chloro­benzoate

The title compound, C8H8ClNO2, is almost planar, with an r.m.s. deviation of 0.0410 Å from the plane through the non-hydrogen atoms. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into chains along the b axis. An intra­molecular N—H⋯O hydrogen bond results in the formation of a six-membered ring

The axial crack testing model for long distance oil-gas pipeline based on magnetic flux leakage internal inspection method

Traditional pipeline magnetic flux leakage (MFL) internal technology mainly uses axial excitation method, which could not recognize the narrow crack defects in the axial direction of the pipe. In this paper, by using a linear magnetic dipole model to study the circumferential excitation method, the detection model of axial crack in pipeline is established, and the relationship between MFL signals and the geometry characteristics of axial cracks is calculated. Finally, the detection accuracy and identification method of axial cracks is analyzed. Research results show that: non-uniform magnetic field generated by circumferential excitation can effectively detect the narrow cracks in the axial direction of the pipeline and distinguish the depth and the width characteristics of cracks. However, the background magnetic fields near the magnetic poles have great influence on the detection accuracy, and the smooth interpolation method of the cubic-spline interpolation can be used to reduce the influence effectively

4-Tosyl-1-oxa-4-aza­spiro­[4.5]deca-6,9-dien-8-one

In the mol­ecule of the title compound, C15H15NO4S, the two six-membered rings are almost parallel to each other [dihedral angle = 1.87 (9)°] and perpendicular to the mean plane through the five-membered ring [dihedral angles of 89.98 (10) and 89.04 (10)°]. The crystal structure is stabilized by inter­molecular C—H⋯O hydrogen-bonding inter­actions

Methyl 5-chloro-2-[N-(3-eth­oxy­carbonyl­prop­yl)-4-methyl­benzene­sulfonamido]­benzoate

In the title compound, C21H24ClNO6S, the benzene rings are oriented at a dihedral angles of 41.6 (2)°. In the crystal structure, weak inter­molecular C—H⋯O inter­actions link the mol­ecules

Geometry and optics calibration of WFCTA prototype telescopes using star light

The Large High Altitude Air Shower Observatory project is proposed to study high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20 TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component of the LHAASO project, will be used to study energy spectrum and compositions of cosmic ray by measuring the total Cherenkov light generated by air showers and shower maximum depth. Two prototype telescopes have been in operation since 2008. The pointing accuracy of each telescope is crucial to the direction reconstruction of the primary particles. On the other hand the primary energy reconstruction relies on the shape of the Cherenkov image on the camera and the unrecorded photons due to the imperfect connections between photomultiplier tubes. UV bright stars are used as point-like objects to calibrate the pointing and to study the optical properties of the camera, the spot size and the fractions of unrecorded photons in the insensitive areas of the camera.Comment: 5 pages, 6 figures, submitted to Chinese Physics

Methyl 5-chloro-2-(4-methyl­benzene­sulfonamido)­benzoate

In the title compound, C15H14ClNO4S, the benzene rings are oriented at a dihedral angle of 85.42 (1)°. An intra­molecular N—H⋯O hydrogen bond results in the formation of a five-membered ring and an intramolecular C—H⋯O inter­action also occurs