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Full Torus Electromagnetic Gyrokinetic Particle Simulations with Kinetic Electrons

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Communications in Computational physics 2009年第1期5卷 183-194页

作者： Y.Nishimura Z.lin l.Chen department of physics and astronomy University of CaliforniaIrvine92697-4575USA

The full torus electromagnetic gyrokinetic particle simulations using the hybrid model with kinetic electrons in the presence of magnetic shear is *** fluid-kinetic electron hybrid model employed in this paper improves numerical properties by removing the tearing mode,meanwhile,preserves both linear and nonlinear wave-particle resonances of electrons with Alfven wave and ion acoustic wave.

关键词： Gyrokinetic particle simulation plasma turbulence electromagnetic gyrokinetic theory

Unitary fermions and lscher's formula on a crystal

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Science China(physics,Mechanics & astronomy) 2016年第11期59卷 36-43页

作者： Manuel Valiente Nikolaj T.Zinner SUPA Institute of Photonics and Quantum Sciences Heriot-Watt University department of physics & astronomy Aarhus University

We consider the low-energy particle-particle scattering properties in a periodic simple cubic crystal. In particular, we investigate the relation between the two-body scattering length and the energy shift experienced by the lowest-lying unbound state when this is placed in a periodic finite box. We introduce a continuum model for s-wave contact interactions that respects the symmetry of the Brillouin zone in its regularisation and renormalisation procedures, and corresponds to the nae continuum limit of the Hubbard model. The energy shifts are found to be identical to those obtained in the usual spherically symmetric renormalisation scheme upon resolving an important subtlety regarding the cutoff procedure. We then particularize to the Hubbard model, and find that for large finite lattices the results are identical to those obtained in the continuum limit. The results reported here are valid in the weak,intermediate and unitary limits. These may be used to significantly ease the extraction of scattering information, and therefore effective interactions in condensed matter systems in realistic periodic potentials. This can achieved via exact diagonalisation or Monte Carlo methods, without the need to solve challenging, genuine multichannel collisional problems with very restricted symmetry simplifications.

关键词： scattering theory effective field theory lattice fermions finite-size effects

Observing quantum coherence from photons scattered in free-space

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light(Science & Applications) 2021年第7期10卷 1304-1312页

作者： Shihan Sajeed Thomas Jennewein Institute for Quantum Computing University of WaterlooWaterlooON N2L 3G1Canada department of physics and astronomy University of WaterlooWaterlooON N2L 3G1Canada

Quantum channels in free-space,an essential prerequisite for fundamental tests of quantum mechanics and quantum technologies in open space,have so far been based on direct line-of-sight because the predominant approaches for photon-encoding,including polarization and spatial modes,are not compatible with randomly scattered *** we demonstrate a novel approach to transfer and recover quantum coherence from scattered,non-line-of-sight photons analyzed in a multimode and imaging interferometer for time-bins,combined with photon detection based on a 8×8 *** observed time-bin visibility for scattered photons remained at a high 95%over a wide scattering angle range of−45^(0) to+45^(0),while the individual pixels in the detector array resolve or track an image in its field of view of ca.0.5°.Using our method,we demonstrate the viability of two novel ***,using scattered photons as an indirect channel for quantum communication thereby enabling non-line-of-sight quantum communication with background suppression,and secondly,using the combined arrival time and quantum coherence to enhance the contrast of low-light imaging and laser ranging under high background *** believe our method will instigate new lines for research and development on applying photon coherence from scattered signals to quantum sensing,imaging,and communication in free-space environments.

关键词： scattered quantum photons

Resistance fluctuations in superconducting K_(x)Fe_(2-y)Se_(2) single crystals studied by low-frequency noise spectroscopy

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Chinese physics B 2021年第4期30卷 502-507页

作者： Hai Zi Yuan Yao Ming-Chong He Di Ke Hong-Xing Zhan Yu-Qing Zhao Hai-Hu Wen Cong Re physics department School of Physics and AstronomyYunnan UniversityKunming 50500China Beijing National laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of ScienceBeijing 100190China physics department Nanjing UniversityNanjing 210093China

low-frequency resistance noise spectroscopy is applied to investigate bulk single crystals of the intercalated ironselenide K_(x)Fe_(2-y)Se_(2) superconductors with different iron vacancy *** on a generalized fluctuation model,the well-observed resistance hump above 100 K is interpreted as an insulator-metal phase transition with a characteristic transition energy of 0.1-0.6 eV,indicating a highly inhomogeneous energy distribution *** the superconducting transition regime,we find that the normalized resistance noise scales with resistance R excellently as S_(R)/R^(2)∝R^(l_(rs)) with the noise exponent lrs≈*** reduced iron vacancy disordering in enhanced superconductivity K_(x)Fe_(2-y)Se_(2) crystals,the level of resistance fluctuations is greatly suppressed,suggesting a geometrical phase transition for conduction channel,which is directly related to the microstructure of the crystals.

关键词： K_(x)Fe_(2-y)Se_(2) phase separation noise and chaos percolation

Spherical/gyroid phase diagram of the diblock copolymer in the median selective solvent

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Science China(physics,Mechanics & astronomy) 2009年第4期52卷 518-523页

作者： ZHANG lingYun WANG PengYe SHI An-Chang laboratory of Soft Matter physics Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing 100190China department of physics and astronomy McMaster UniversityHamiltonOntarioCanada L8S 4M1

The effect of the median selective solution on the lamellar,spherical and gyroid structures is studied. The self-consistent field equations of the diblock copolymer solution are solved by using the reciprocal space method. It is shown that the spherical and gyroid phases have the lowest free energy in the certain range of the solution concentration. Furthermore,the phase diagram of the ordered structures in the diblock copolymer solution with the median selective solvent is calculated,which is consistent with the experimental results.

关键词： self-consistent field theory diblock copolymer solution phase diagram reciprocal space method

Cataclysmic variables based on the stellar spectral survey lAMOST DR3

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Research in astronomy and Astrophysics 2018年第6期18卷 67-88页

作者： Xianming l.Han li-Yun Zhang Jian-Rong Shi Qing-Feng Pi Hong-Peng lu li-Bo Zhao Rachel K.Terheide lin-Yang Jiang College of physics/department of physics and astronomy & Guizhou Provincial Key laboratory of Public Big Data Guizhou University Dept.of physics and astronomy Butler University Key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences department of astronomy Beijing Normal University

Big data in the form of stellar spectra from the spectroscopic survey associated with the large Sky Area Multi-object Fiber Spectroscopic Telescope(lAMOST) are important for studying properties of cataclysmic variables(CVs). By cross matching the catalogs of CVs compiled with lAMOST DR3,acquired from October 2011 to July 2015, we obtained the first spectroscopic catalog for CVs observed by lAMOST with high signal to noise ratio, above 8. By integrating line profiles, their equivalent widths(EWs) of the Hα, Hβ, Hγ and Hδ, as well as He I 5876 and 6678 A? lines, were calculated. There were74 stellar spectra from 48 known CVs and three spectra from three new CV candidates. At the same time, we also collected their previously published EWs. Thirty-three objects had repeated spectra and30 stars showed spectral variability in the Hα line. Moreover, we carried out photometric follow-up studies for five CVs(UU Aqr, TT Tri, PX And, BP lyn and RW Tri). We obtained nine new light curves and revised their linear ephemerides. For RW Tri, there is a possible oscillation with an amplitude of0.0031(2) days and a period of 47.6±0.4 years, which might be caused by a third body(brown dwarf)or magnetic activity cycle.

关键词： stars: cataclysmic variables stars: spectroscopic stars: variable

Photon sphere and phase transition of ddimensional(d≥5) charged Gauss–Bonnet AdS black holes

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Communications in Theoretical physics 2020年第10期72卷 131-138页

作者： Shan-Zhong Han Jie Jiang Ming Zhang Wen-Biao liu department of physics Beijing Normal UniversityBeijing 100875China College of physics and Communication Electronics Jiangxi Normal UniversityNanchang 330022China Perimeter Institute for Theoretical physics WaterlooOntario N2L 2Y5Canada department of physics and astronomy University of WaterlooOntario N2L 3G1Canada

Motivated by recent work,nonmonotonic behaviors of photon sphere radius can be used to reflect black hole phase transition for Reissner–Nordstr?m–AdS(RN–AdS)black holes,we study the case of five-dimensional charged Gauss–Bonnet–AdS black holes in the reduced parameter *** find that the nonmonotonic behaviors of photon sphere radius still *** the coexistence line calculated from P–V plane,we capture the photon sphere radius of saturated small and large black holes(the boundary of the coexistence phase),then illustrate the reduced coexistence *** results show that,reduced coexistence region decreases with charge Q but increases with Gauss–Bonnet coefficientα.When the charge vanishes,reduced coexistence region does not vary with Gauss–Bonnet coefficientαany *** this case,the Gauss–Bonnet coefficientαplays the same role as the charge of five-dimensional RN–AdS black ***,the situation of higher dimension is studied in the end.

关键词： Gauss–Bonnet AdS black hole phase transition photon sphere black hole thermodynamics

Null geodesics,quasinormal modes,and thermodynamic phase transition for charged black holes in asymptotically flat and dS spacetimes

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Chinese physics C 2020年第11期44卷 220-231页

作者： Shao-Wen Wei Yu-Xiao liu Institute of Theoretical physics&Research Center of Gravitation Lanzhou UniversityLanzhou 730000China department of physics and astronomy University of WaterlooWaterlooOntarioN2L 3G1Canada

A numerical study has indicated that there exists a relation between the quasinormal modes and the Davies point for a black *** this paper,we analytically study this relation for charged Reissner-Nordstrom black holes in asymptotically flat and de Sitter(dS)spacetimes in the eikonal limit,under which the quasinormal modes can be obtained from the null geodesics using the angular velocity Ω and the lyapunov exponentλof the photon *** in asymptotically flat and dS spacetimes,we observe spiral-like shapes in the complex quasinormal mode ***,the starting point of the shapes does not coincide with the Davies ***,we find a new relation in which the Davies point exactly meets the maximum temperature T in the T-Ω and T-λ *** a higher-dimensional asymptotically flat spacetime,although there is no spiral-like shape,such a relation still ***,we provide a new relation between black hole thermodynamics and dynamics in the eikonal *** this relation,we can test the thermodynamic property of a black hole using the quasinormal modes.

关键词： black holes phase transition photon sphere

High-pressure Mossbauer Study of Metastable 304 Stainless Steel with bcc Structure

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Chinese physics letters 1995年第4期12卷 241-244页

作者： lI Fashen SUN Jijun C.l.Chien department of physics Lanzhou UniversityLanzhou 730000 department of physics and astronomy The Johns Hopkins UniversityBaltimoreMaryland 21218U.S.A.

The ferromagnetic metastable bcc 304 stainless steel film was studied by means of ^(57)Fe high-pressure Mossbauer *** fcc phase was observed under the pressure up to 36 ***,the magnetization direction of the sample was found to reorientate under the high-pressure,and showed the strongest tendency to the out-of-plane under the pressure 8 kbar,then was gradually close to the in-plane with increasing pressure.

关键词： spectroscopy. steel Mossbauer