检索结果-南通市图书馆

New evidence for lack of CMB power on large scales

在线全文

学校读者我要写书评

暂无评论

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, {2. 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

在线全文

学校读者我要写书评

暂无评论

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,{2. 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 & {2. for {3. Tsinghua University Beijing China department of Engineering physics & {2. for {3. 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

Bifurcation timescales in power spectra of black hole binaries and ultraluminous X-ray sources

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 177-182页

作者： wang taishan1 & LI TiPei1,2.1 {2. of physics & center for astrophysics,tsinghua university,beijing 100084,china 2.Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,{13. 100049,china tsinghua Univ Dept Phys Beijing 100084 Peoples R China tsinghua Univ Ctr Astrophys Beijing 100084 Peoples R China Chinese Acad Sci Inst High Energy Phys Key Lab Particle Astrophys Beijing 100049 Peoples R China

For black hole binaries(BHBs) and active galactic nuclei(AGNs),bifurcation timescales(BTs) Δtb exist,below which time-domain power is significantly higher than the corresponding Fourier ***-periodic oscillations(QPOs) are removed from the Fourier spectra of BHBs.A relationship between BT,black hole mass and bolometric luminosity is *** anti-correlation between BT and luminosity of Cyg X-1 is *** removing the QPOs,BTs are also obtained for two ultraluminous X-ray sources(ULXs),M82.X-1 and NGC5408 *** results support that they harbor intermediate mass black holes(IMBHs).

关键词： black hole binary ultraluminous X-ray source power spectral density data analysis

Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第10期17卷 1147-1151页

作者： Liu Dan1,2., Zhang Yong3.and Long Guilu1,2.1. Key Laboratory for Atomic and Molecular NanoSciences, and department of {3., {2., beijing 100084, china 2. center of Quantum Information Science and Technology, tsinghua National Laboratory for information Science and Technology, beijing 100084, china 3. Institute of {3., School of Sciences, {13. university of Posts and Telecommunications, {13. 100876, china) Key Laboratory for Atomic and Molecular NanoSciences and Department of Physics Tsinghua University Beijing 100084 China center of Quantum Information Science and Technology Tsinghua National Laboratory for information Science and Technology Beijing 100084 China Institute of physics School of Sciences Beijing University of Posts and Telecommunications Beijing 100876 China

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ>3. namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.

关键词： Heisenberg-XY chain magnetic-current phase transition.

Experimental realization of quantum cryptography communication in free space

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2005年第2期48卷 237-246页

作者： wang Chuan1, ZHANG Jingfu1, wang Pingxiao1, DENG Fuguo1, AI Qing1 & LONG Guilu1,2.1. {2. of physics, Key Laboratory for Quantum Information and Measurements, tsinghua Univer- sity, beijing 100084, china 2. center for Atomic and Molecular NanoSciences, tsinghua university, beijing 100084, china department of physics Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing 100084 China Atomic and Molecular NanoSciences Tsinghua University Beijing 100084 China

Utilizing linear optical devices, the principle of B92.quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2.meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.

关键词： quantum key distribution, free space, linear optics, faint pulses.

Implementation of a multiple round quantum dense coding using nuclear magnetic resonance

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2005年第6期48卷 706-715页

作者： ZHANG Jingfu1, XIE Jingyi2. wang Chuan1, DENG Zhiwei3. LU Zhiheng4, & LONG Guilu1,5 1. Key Laboratory For Quantum Information and Measurements of MOE, department of {2., tsinghua university, beijing 100084,china 2. department of Materials Science and Engineering, beijing Normal university, beijing 100875, china 3. Testing and Analytical {13., beijing Normal university, beijing 100875,china 4. department of {2., beijing Normal university, beijing 100875, china 5. Key Laboratory For atomic and Molecular Nanosciences, tsinghua university, beijing 100084,china 1. Key Laboratory For Quantum Information and Measurements of MOE Department of Physics Tsinghua University 100084 Beijing China 2. department of Materials science and Engineering Beijing Normal University 100875 Beijing China 3. Testing and Analytical center Beijing Normal University 100875 Beijing China 4. department of physics Beijing Normal University 100875 Beijing China 5. Key Laboratory For Atomic and Molecular Nanosciences Tsinghua University 100084 Beijing China

A multiple round quantum dense coding scheme based on the quantum phase estimation algorithm is proposed and implemented in a three qubit nuclear magnetic resonance (NMR) quantum computer. Using an m + 1 qubit system, Bob can transmit one of 2.+1 messages to Alice, through manipulating only one qubit and exchanging it between Alice and Bob for m rounds. The information capacity is enhanced to m + 1 bits as compared to m bits in a classical scheme. The scheme has been demonstrated in NMR system, and the experimental results show a good agreement between theory and experiment.

关键词： quantum dense coding, multiple round, nuclear magnetic resorance

Timing in the Time Domain: Cygnus X-1

在线全文

学校读者我要写书评

暂无评论

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 {2. for {3., tsinghua university, beijing 100084 High Energy {3. Lab., Institute of High Energy physics, Chinese Academy of Sciences, beijing 10003.)E-mail:litp@*** department of physics and {2. for {3. 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

Diagnostics for the structure of AGNs'broad line regions with reverberation mapping data:confirmation of the two-component broad line region model

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 196-201页

作者： ZHU Ling1 & ZHANG ShuangNan2.1 department of physics and {2. 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 1. department of physics and {2. {3. 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

We re-examine the ten Reverberation Mapping(RM) sources with public data based on the two-component model of the Broad Line Region(BLR).In fitting their broad Hβ Mlines,six of them only need one Gaussian component,one of them has a double-peak profile,one has an irregular profile,and only two of them need two components,i.e.,a Very Broad Gaussian Component(VBGC) and an Inter-Mediate Gaussian Component(IMGC).The Gaussian components are assumed to come from two distinct regions in the two-component model;they are the Very Broad Line Region(VBLR) and the Inter-Mediate Line region(IMLR).The two sources with a two-component profile are Mrk 509 and NGC *** time lags of the two components of both sources satisfy tIMLR/tVBLR=V 2.BLR/V 2.MLR,where tIMLR and tVBLR are the lags of the two components while VIMLR and VVBLR represent the mean gas velocities of the two regions,supporting the two-component model of the BLR of Active Galactic Nuclei(AGNs).The fact that most of these ten sources only have the VBGC confirms the assumption that RM mainly measures the radius of the VBLR;consequently,the radius obtained from the R-L relationship mainly represents the radius of ***,NGC 4051,with a lag of about 5 days in the one component model,is an outlier on the R-L relationship as shown in Kaspi et al.(2.05);however this problem disappears in our two-component model with lags of about 2.and 6 days for the VBGC and IMGC,respectively.

关键词： broad line region AGN Reverberation Mapping cross correlation

GRB 09042.:Marking the death of a massive star at z=8.2

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 64-68页

作者： LIN Lin1,LIANG EnWei2.& ZHANG ShuangNan3.1 department of physics and {2. for astrophysics,tsinghua university,beijing 100084,china 2.department of physics,Guangxi university,Nanning 53.004,china 3.Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,beijing 100049,china Guangxi Univ Dept Phys Nanning 530004 Peoples R China tsinghua Univ Dept Phys Beijing 100084 Peoples R China tsinghua Univ Ctr Astrophys Beijing 100084 Peoples R China Chinese Acad Sci Inst High Energy Phys Key Lab Particle Astrophys Beijing 100049 Peoples R China

GRB 09042. is the new high-z record holder of Gamma-ray bursts(GRBs) with *** present a detailed analysis of both the spectral and temporal features of GRB 09042. observed with Swift/BAT and Fermi/*** find that the T90 observed with BAT in the 15-150 keV band is 13.2.s,corresponding to-1.4 s at z=*** once again gives rise to the issue of whether the progenitors of high-z GRBs are massive stars or mergers since the discovery of GRB 080913.at z=*** comparison with the T90 distribution in the burst frame of the current redshift-known GRB sample,we find that it is marginally grouped into the long group(Type II GRBs).The spectrum observed with both BAT and GBM is well fitted by a power-law with exponential cutoff,which yields an Ep=(50.4±7.0) *** event satisfies the Amati-relation well for Type II GRBs within their 3. uncertainty *** results indicate that this event would be produced by the death of a massive *** on the Amati-relation,we derive its distance modulus,which follows the Hubble diagram of the concordance cosmology model at a redshift of-8.2.

关键词： gamma-ray bursts high energy phenomenon cosmology