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Accelerated Gravitational Wave Parameter Estimation with Reduced Order Modeling

Physical Review Letters 2015年第7期114卷 071104-071104页

作者： Priscilla Canizares Scott E. Field Jonathan Gair Vivien Raymond Rory Smith Manuel Tiglio Institute of Astronomy Madingley Road Cambridge CB3 0HA United Kingdom Department of Applied Mathematics and Theoretical Physics Wilberforce Road Cambridge CB3 0WA United Kingdom Department of Physics Joint Space Sciences Institute Maryland Center for Fundamental Physics University of Maryland College Park Maryland 20742 USA Center for Radiophysics and Space Research Cornell University Ithaca New York 14853 USA LIGO California Institute of Technology Pasadena California 91125 USA Center for Astrophysics and Space Sciences Center for Computational Mathematics San Diego Supercomputer Center University of California San Diego 9500 Gilman Drive La Jolla California 92093-0424 USA

Inferring the astrophysical parameters of coalescing compact binaries is a key science goal of the upcoming advanced LIGO-Virgo gravitational-wave detector network and, more generally, gravitational-wave astronomy. However, current approaches to parameter estimation for these detectors require computationally expensive algorithms. Therefore, there is a pressing need for new, fast, and accurate Bayesian inference techniques. In this Letter, we demonstrate that a reduced order modeling approach enables rapid parameter estimation to be performed. By implementing a reduced order quadrature scheme within the LIGO Algorithm Library, we show that Bayesian inference on the 9-dimensional parameter space of nonspinning binary neutron star inspirals can be sped up by a factor of ∼30 for the early advanced detectors’ configurations (with sensitivities down to around 40 Hz) and ∼70 for sensitivities down to around 20 Hz. This speedup will increase to about 150 as the detectors improve their low-frequency limit to 10 Hz, reducing to hours analyses which could otherwise take months to complete. Although these results focus on interferometric gravitational wave detectors, the techniques are broadly applicable to any experiment where fast Bayesian analysis is desirable.

关键词： Gravity waves

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Development of a Calculation Code System for Evaluation of Deuteron Nuclear Data

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Energy Procedia 2015年 71卷 219-227页

作者： Shinsuke Nakayama Shouhei Araki Yukinobu Watanabe Osamu Iwamoto Tao Ye Kazuyuki Ogata Department of Advanced Energy Engineering Science Kyushu University 6-1 Kasuga-kouen Kasuga-shi Fukuoka 816-8580 Japan Nuclear Science and Engineering Directorate Japan Atomic Energy Agency 2-4 Shirakata-Shirane Tokai-mura Naka-gun Ibaraki 319-1195 Japan Institute of Applied Physics and Computational Mathematics Beijing 100094 China Research Center for Nuclear Physics (RCNP) Osaka University 10-1 Mihogaoka Ibaraki-shi Osaka 567-0047 Japan

A calculation code system for evaluation of deuteron nuclear data is extended so that the stripping reaction to bound states in the residual nucleus can be taken into account properly using a conventional zero-range DWBA approach. The code system is applied to deuteron induced-reactions on 27 Al for incident energies up to 100 MeV. It is found that the spectroscopic factors derived from the present DWBA analysis have incident energy dependence. The calculation using the extended code system reproduces experimental double-differential cross sections for the 27 Al(d,xp) reaction at 25.5, 56, and 100 MeV, and production cross sections of 28 Al in the incident energy range from the threshold to 20 MeV.

关键词： Deuteron-induced Reaction Calculation Code System Double-differential Cross Section Production Cross Section DWBA

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Enhanced Correlation of Electron-Positron Pair in Two and Three Dimensions

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Chinese physics Letters 2014年第1期31卷 48-51页

作者：唐琐谢柏松王虹宇刘杰傅立斌郁明阳 Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education College of Nuclear Science and Technology Beijing Normal University Beijing 100875 Department of Physics Anshan Normal University Anshan 114005 Institute of Applied Physics and Computational Mathematics P. O. Box 8009 Beijing 100088 Institute for Fusion Theory and Simulation Department of Physics Zhejiang University Hangzhou 310027 Institut fur Theoretische Physik I Ruhr-Universigt Bochum D-44780 Bochum Germany

Early time electron-positron correlation in vacuum pair-production in an external field is investigated. The entangled electron and positron wave functions are obtained analytically in the configuration and momentum spaces. It is shown that, relative to that of the one-dimensional theory, two- and three-dimensional calculations yield enhanced spatial correlation and broadened momentum spectra. In fact, at early times the electron and positron almost coincide spatially. The correlation also depends on the direction of the applied field. For the spatial correlation, the transverse correlation is stronger than the longitudinal correlation.

关键词： Positrons

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Novel Conservative Methods for Schrödinger Equations with Variable Coefficients over Long Time

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Communications in computational physics 2014年第3期15卷 692-711页

作者： Xu Qian Yaming Chen Songhe Song Department of Mathematics and Systems Science and State Key Laboratory of High Performance ComputingNational University of Defense TechnologyChangsha 410073P.R.China Program in Applied and Computational Mathematics Princeton UniversityPrincetonNJ 08544USA School of Mathematical Sciences Queen Mary University of LondonLondon E14NSUK

In this paper,we propose a wavelet collocation splitting(WCS)method,and a Fourier pseudospectral splitting(FPSS)method as comparison,for solving onedimensional and two-dimensional Schrödinger equations with variable coefficients in quantum *** two methods can preserve the intrinsic properties of original problems as much as *** splitting technique increases the computational ***,the error estimation and some conservative properties are *** is proved to preserve the charge conservation *** global energy and momentum conservation laws can be preserved under several *** experiments are conducted during long time computations to show the performances of the proposed methods and verify the theoretical analysis.

关键词： Schrödinger equation wavelet collocation method splitting technique conservative property

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High-order rogue waves in vector nonlinear Schrödinger equations

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Physical Review E 2014年第4期89卷 041201(R)-041201(R)页

作者： Liming Ling Boling Guo Li-Chen Zhao Department of Mathematics South China University of Technology Guangzhou 510640 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Physics Northeast University Xi'an 710069 China

We study the dynamics of high-order rogue waves (RWs) in two-component coupled nonlinear Schrödinger equations. We find that four fundamental rogue waves can emerge from second-order vector RWs in the coupled system, in contrast to the high-order ones in single-component systems. The distribution shape can be quadrilateral, triangle, and line structures by varying the proper initial excitations given by the exact analytical solutions. The distribution pattern for vector RWs is more abundant than that for scalar rogue waves. Possibilities to observe these new patterns for rogue waves are discussed for a nonlinear fiber.

关键词： Nonlinear equations

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Multi-timescale analysis of phase transitions in precessing black-hole binaries

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Physical Review D 2015年第6期92卷 064016-064016页

作者： Davide Gerosa Michael Kesden Ulrich Sperhake Emanuele Berti Richard O’Shaughnessy Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom Department of Physics The University of Texas at Dallas Richardson Texas 75080 USA Department of Physics and Astronomy The University of Mississippi University Mississippi 38677 USA California Institute of Technology Pasadena California 91125 USA CENTRA Departamento de Física Instituto Superior Técnico Universidade de Lisboa Avenida Rovisco Pais 1 1049 Lisboa Portugal Center for Computational Relativity and Gravitation Rochester Institute of Technology Rochester New York 14623 USA

The dynamics of precessing binary black holes (BBHs) in the post-Newtonian regime has a strong timescale hierarchy: the orbital timescale is very short compared to the spin-precession timescale which, in turn, is much shorter than the radiation-reaction timescale on which the orbit is shrinking due to gravitational-wave emission. We exploit this timescale hierarchy to develop a multiscale analysis of BBH dynamics elaborating on the analysis of Kesden et al. [Phys. Rev. Lett. 114, 081103 (2015)]. We solve the spin-precession equations analytically on the precession time and then implement a quasiadiabatic approach to evolve these solutions on the longer radiation-reaction time. This procedure leads to an innovative “precession-averaged” post-Newtonian approach to studying precessing BBHs. We use our new solutions to classify BBH spin precession into three distinct morphologies, then investigate phase transitions between these morphologies as BBHs inspiral. These precession-averaged post-Newtonian inspirals can be efficiently calculated from arbitrarily large separations, thus making progress towards bridging the gap between astrophysics and numerical relativity.

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Scaling Laws of the Two-Electron Sum-Energy Spectrum in Strong-Field Double Ionization

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Physical Review Letters 2015年第12期115卷 123001-123001页

作者： Difa Ye Min Li Libin Fu Jie Liu Qihuang Gong Yunquan Liu J. Ullrich Institute of Applied Physics and Computational Mathematics Beijing 100088 People’s Republic of China Department of Physics and State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 People’s Republic of China Collaborative Innovation Center of Quantum Matter Beijing 100871 People’s Republic of China CAPT HEDPS and IFSA Collaborative Innovation Center of MoE Peking University Beijing 100871 People’s Republic of China Center for Fusion Energy Science and Technology China Academy of Engineering Physics Beijing 100088 People’s Republic of China Max-Planck-Institut für Kernphysik Saupfercheckweg 1 69117 Heidelberg Germany Physikalisch-Technische Bundesanstalt Bundesallee 100 38116 Braunschweig Germany

The sum-energy spectrum of two correlated electrons emitted in nonsequential strong-field double ionization (SFDI) of Ar was studied for intensities of 0.3 to 2×1014 W/cm2. We find the mean sum energy, the maximum of the distributions as well as the high-energy tail of the scaled (to the ponderomotive energy) spectra increase with decreasing intensity below the recollision threshold (BRT). At higher intensities the spectra collapse into a single distribution. This behavior can be well explained within a semiclassical model providing clear evidence of the importance of multiple recollisions in the BRT regime. Here, ultrafast thermalization between both electrons is found occurring within three optical cycles only and leaving its clear footprint in the sum-energy spectra.

关键词： Ionization of gases

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Precessional Instability in Binary Black Holes with Aligned Spins

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Physical Review Letters 2015年第14期115卷 141102-141102页

作者： Davide Gerosa Michael Kesden Richard O’Shaughnessy Antoine Klein Emanuele Berti Ulrich Sperhake Daniele Trifirò Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom Department of Physics The University of Texas at Dallas Richardson Texas 75080 USA Center for Computational Relativity and Gravitation Rochester Institute of Technology Rochester New York 14623 USA Department of Physics and Astronomy The University of Mississippi University Mississippi 38677 USA CENTRA Departamento de Física Instituto Superior Técnico Universidade de Lisboa Avenida Rovisco Pais 1 1049 Lisboa Portugal California Institute of Technology Pasadena California 91125 USA Dipartimento di Fisica E. Fermi Università di Pisa Pisa 56127 Italy

Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values rud±=(χ1±qχ2)4(1−q)−2M, where M is the total mass, q≡m2/m1 is the mass ratio, and χ1 (χ2) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.

关键词： General relativity equations & solutions Gravitational waves

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The origin of self-focusing effect in terahertz quantum cascade lasers

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Journal of physics: Conference Series 2015年第1期574卷

作者： Jian Wang Yanfang Li Ning Yang Department of Physics Beijing Jiaotong University 100044 Beijing China Institute of Applied Physics and Computational Mathematics PO Box 8009(28) 100088 Beijing China

The terahertz quantum cascade lasers (THz-QCLs) are the compact and coherent terahertz light sources based on the inter-subband transition and resonant tunneling of carriers in semiconductor superlattice. In recent studies on tapered THz-QCLs, it was found that the self-focusing effect in the active region of the devices may cause the abnormal increase of the far-field divergence of the laser beam. By simulating the propagation of optical mode in QCL waveguide and considering both the nonlinearity effect and thermal accumulation in the active region, we propose that the refractive index change caused by the third-order nonlinearity of multi-quantum-wells in active region may be the key reason for the self-focusing in THz-QCLs. This result indicates that the nonlinear effect may have great impact on the beam quality of QCLs which must be carefully considered in applications of THz-QCLs, such as the TH- imaging systems.

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Determining the resistance of X-pinch plasma

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Chinese physics B 2013年第4期22卷 344-349页

作者：赵屾薛创朱鑫磊张然罗海云邹晓兵王新新宁成丁宁束小建 Department of Electrical Engineering Tsinghua University Institute of Applied Physics and Computational Mathematics

The current and the voltage of an X-pinch were measured. The inductance of the X-pinch was assumed to be a constant and estimated by the calculation of the magnetic field based on the well-known Biot–Savart’s Law. The voltage of the inductance was calculated with L · di/dt and subtracted from the measured voltage of the X-pinch. Then, the resistance of the X-pinch was determined and the following results were obtained. At the start of the current flow the resistance of the exploding wires is several tens of Ohms, one order of magnitude, higher than the metallic resistance of the wires at room temperature, and then it falls quickly to about 1 , which reflects the physical processes occurring in the electrically exploding wires, i.e., a current transition from the highly resistive wire core to the highly conductive plasma. It was shown that the inductive contribution to the voltage of the X-pinch is less than the resistive contribution. For the wires we used, the wires’ material and diameter have no strong influence on the resistance of the X-pinch, which may be explained by the fact that the current flows through the plasma rather than through the metallic wire itself. As a result, the current is almost equally divided between two parallel X-pinches even though the diameter and material of the wires used for these two X-pinches are significantly different.

关键词： electrical explosion of wires X-pinch Z-pinch

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