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Constraints on Cardassian universe from Gamma ray bursts

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Science china(physics,Mechanics & Astronomy) 2010年第9期53卷 1720-1725页

作者： wang taishan1 & liANG Nan2 1 department of physics & center for astrophysics,tsinghua university,beijing 100084,china 2 department of Astronomy,beijing Normal university,beijing 100875,china 1. department of physics & center for astrophysics Tsinghua University Beijing 100084 China2. Department of Astronomy Beijing Normal University Beijing 100875 China

Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the recently derived 42 gamma-ray bursts(GRBs) data calibrated with the method that can avoid the circularity *** results show that GRBs can be an optional observation to constrain the Cardassian *** the GRBs data with the newly de-rived size of baryonic acoustic oscillation peak from the Sloan Digital Sky Survey(SDSS),and the position of the first acoustic peak of the Cosmic Microwave Background radiation(CMB) from Wilkinson Microwave Anisotropy Probe(WMAP),we find Ωm0=0.27+0.02-0.02,n=0.06+0.07-0.08(1σ) for the original Cardassian model,and Ωm0=0.27+0.23-0.02,n=-0.09+0.23-1.91,β=0.82+2.10-0.62(1σ) for the modified polytropic Cardassian model.

关键词： Cardassian Gamma ray burst Cosmic Microwave Background baryonic acoustic oscillation

New evidence for lack of CMB power on large scales

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Science china(physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： liU Hao1 & li tipei1,2,3 1 Key Laboratory of Particle astrophysics, Institute of High Energy physics, Chinese Academy of Sciences, beijing 100049, china 2 department of physics & center for astrophysics, tsinghua university, beijing 100084, china 3 department of Engineering physics & center for astrophysics, tsinghua university, beijing 100084, china 1. Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China2. Department of Physics & Center for Astrophysics Tsinghua University Beijing 100084 China3. Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing 100084 China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

Inconsistency between WMAP data and released map

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Chinese Science Bulletin 2010年第10期55卷 907-909页

作者： liU Hao1 & li tipei1,2,3 1 Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,beijing 100049,china 2 department of physics & center for astrophysics,tsinghua university,beijing 100084,china 3 department of Engineering physics & center for astrophysics,tsinghua university,beijing 100084,china Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China department of physics & center for astrophysics Tsinghua University Beijing China department of Engineering physics & center for astrophysics Tsinghua University Beijing China

A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (CMB) temperature maps published by the WMAP team is revealed,indicating that there must exist a serious problem in the map making routine of the WMAP *** inconsistency is easy to be confirmed without the use of WMAP map-making *** view of the importance of this issue for cosmology study,we invite readers to check it by themselves.

关键词：威尔金森微波各向异性探测器 WMAP 地图制作宇宙微波背景有序数据制作软件 TOD CMB

The correlation timescale of the X-ray flux during the outbursts of soft X-ray transients

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Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 161-167页

作者： WU YuXiang1,2,YU WenFei1 & li tipei2 1 Shanghai Astronomical Observatory,Shanghai 100012,china 2 department of Engineering physics & center for astrophysics,tsinghua university,beijing 100084,china Shanghai Astron Observ Shanghai 100012 Peoples R China tsinghua Univ Dept Engn Phys Beijing 100084 Peoples R China tsinghua Univ Ctr Astrophys Beijing 100084 Peoples R China

Recent studies of black hole and neutron star low mass X-ray binaries(LMXBs) show a positive correlation between the X-ray flux at which the low/hard(LH)-to-high/soft(HS) state transition occurs and the peak flux of the following HS *** analyzing the data from the All Sky Monitor(ASM) onboard the Rossi X-ray Timing Explorer(RXTE),we show that the HS state flux after the source reaches its HS flux peak still correlates with the transition flux during soft X-ray transient(SXT) *** studying large outbursts or flares of GX 339-4,Aql X-1 and 4U 1705-44,we have found that the correlation holds up to 250,40,and 50 d after the LH-to-HS state transition,*** time scales correspond to the viscous time scale in a standard accretion disk around a stellar mass black hole or a neutron star at a radius of-104-5 Rg,indicating that the mass accretion rates in the accretion flow either correlate over a large range of radii at a given time or correlate over a long period of time at a given *** the accretion geometry is a two-flow geometry composed of a sub-Keplerian inflow or outflow and a disk flow in the LH state,the disk flow with a radius up to-105 Rg would have contributed to the nearly instantaneous non-thermal radiation directly or indirectly,and therefore affects the time when the state transition occurs.

关键词： accretion disks black hole physics star:individual(Aquila X-1 GX 339-4 4U 1705-44)

The relativistic consistent angular-momentum projected shell model study of the N=Z nucleus ^(52)Fe

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Science china(physics,Mechanics & Astronomy) 2009年第10期52卷 1471-1476页

作者： li YanSong1,2 & LONG GuiLu1,2 1 department of physics,tsinghua university,beijing 100084,china 2 center of Nuclear Theory,National Laboratory of Heavy Ion Accelerator of Lanzhou,Lanzhou 730000,china 1. department of physics Tsinghua University Beijing 100084 China 2. center of Nuclear Theory National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou 730000 China

The relativistic consistent angular-momentum projected shell model(ReCAPS) is used in the study of the structure and electromagnetic transitions of the low-lying states in the N=Z nucleus *** model calculations show a reasonably good agreement with the *** backbending at 12+ is reproduced and the energy level structure suggests that neutron-proton interactions play important roles.

关键词： ReCAPS relativistic mean field angular-momentum projection method 52Fe neutron-proton interaction

Hard X-ray lags of Cygnus X-1 on short timescales

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Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 150-152页

作者： JIN Jing1,LU Yu2,3,QU JinLu2 & li tipei1,2 1 department of Engineering physics & center for astrophysics,tsinghua university,beijing 100084,china 2 Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,beijing 100049,china 3 Graduate university of Chinese Academy of Sciences,beijing 100049,china 1. department of Engineering physics & center for astrophysics Tsinghua University Beijing 100084 China2. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small *** a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin *** new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes *** calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.

关键词： spectral lags Cygnus X-1 data analysis

Timing in the Time Domain: Cygnus X-1

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Chinese Journal of Astronomy and astrophysics 2001年第4期1卷 313-332页

作者： Ti-Pei li (department of physics and center for astrophysics, tsinghua university, beijing 100084 High Energy astrophysics Lab., Institute of High Energy physics, Chinese Academy of Sciences, beijing 100039)E-mail:litp@*** department of physics and center for astrophysics Tsinghua University Beijing 100084 High Energy Astrophysics Lab. Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039

Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.

关键词： methods: data analysis - stars: individual (Cygnus X-1) - X-rays: stars

Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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Science china(physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： li Zhihui1,2, ZHANG Hanxin1 & FU Song2 ⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development center,Mianyang 621000,china 2.department of Engineering Mechanics,tsinghua university,beijing 100084,china 1. National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. department of Engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

Testing local realism in P → VV decays

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Science china(physics,Mechanics & Astronomy) 2010年第5期53卷 870-875页

作者： li Junli1 & QIAO CongFeng1,2 1department of physics,Graduate university of Chinese Academy of Sciences,beijing 100049,china 2Theoretical physics center for Science Facilities(TPCSF),Chinese Academy of Sciences,beijing 100049,china 1. department of physics Graduate University of Chinese Academy of Sciences Beijing 100049 China2. Theoretical Physics Center for Science Facilities (TPCSF) Chinese Academy of Sciences Beijing 100049 China

It was found that the vector meson pair from the pseudoscalar decays can form an entangled *** this work we give out detailed explanations on the polarization correlation of the two entangled vector *** is demonstrated that an experimental test of the Clauser-Horne inequality can be carried out through measuring the azimuthal distribution of four pseudoscalars in the cascade decay ηc→ VV →(PP)(PP),and the measurement of this process is feasible with the current running experiments in tau-charm ***,a brief discussion on the polarization correlation of the two vector mesons from B → VV decays is also presented.

关键词： nonlocality test high energy experiment meson decays