Astrodynamical space test of relativity using optical devices optimized for gravitation wave detection （ASTROD- GW） is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection ...Astrodynamical space test of relativity using optical devices optimized for gravitation wave detection （ASTROD- GW） is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection sensitivity is shifted 52 times toward larger wavelength compared with that of laser interferometer space antenna （LISA）. The mission orbits of the three spacecrafts forming a nearly equilateral triangular array are chosen to be near the Sun–Earth Lagrange points L3, L4, and L5. The three spacecrafts range interferometrically with one another with an arm length of about 260 million kilometers. In order to attain the required sensitivity for ASTROD-GW, laser frequency noise must be suppressed to below the secondary noises such as the optical path noise, acceleration noise, etc. For suppressing laser frequency noise, we need to use time delay interferometry （TDI） to match the two different optical paths （times of travel）. Since planets and other solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the TDI, we simulate the time delay numerically using CGC 2.7 （here, CGC stands for center for gravitation and cosmology） ephemeris framework. To conform to the ASTROD-GW planning, we work out a set of 20-year optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and calculate the differences in optical path in the first and second generation TDIs separately for one-detector case. In our optimized mission orbits of 20 years, changes of arm lengths are less than 0.0003 AU; the relative Doppler velocities are all less than 3m/s. All the second generation TDI for one-detector case satisfies the ASTROD-GW requirement.展开更多
We study the quasinormal modes （QNMs） for stringy black holes. By using numerical calculation, the relations between the QNMs and the parameters of black holes are minutely shown. For （1＋1）-dimensional stringy bl...We study the quasinormal modes （QNMs） for stringy black holes. By using numerical calculation, the relations between the QNMs and the parameters of black holes are minutely shown. For （1＋1）-dimensional stringy black hole, the real part of the quasinormal frequency increases and the imaginary part of the quasinormal frequency decreases as the mass of the black hole increases. Furthermore, the dependence of the QNMs on the charge of the black hole and the flatness parameter is also illustrated. For （1＋3）-dimensional stringy black hole, increasing either the event horizon or the multipole index, the real part of the quasinormal frequency decreases. The imaginary part of the quasinormal frequency increases no matter whether the event horizon is increased or the multipole index is decreased.展开更多
A new cosmological model based on the de Sitter gravity is investigated by dynamical analysis and numerical discussions.Via some transformations,the evolution equations of this model can form an autonomous system with...A new cosmological model based on the de Sitter gravity is investigated by dynamical analysis and numerical discussions.Via some transformations,the evolution equations of this model can form an autonomous system with 8 physical critical points.Among these critical points there exist one positive attractor and one negative attractor.The positive attractor describes the asymptotic behavior of late-time universe,which indicates that the universe will enter the exponential expansion phase,finally.Some numerical calculations are also carried out,which convince us of this conclusion derived from the dynamical analysis.展开更多
We study the semi-holographic idea in the context of decaying dark components.The energy flow between dark energy and the compensating dark matter is thermodynamically generalized to involve a particle number variable...We study the semi-holographic idea in the context of decaying dark components.The energy flow between dark energy and the compensating dark matter is thermodynamically generalized to involve a particle number variable dark component with non-zero chemical potential.It is found that,unlike the original semi-holographic model,no cosmological constant is needed for a dynamical evolution of the universe.A transient phantom phase appears while a non-trivial dark energy-dark matter scaling solution stays at a later time,which evades the big-rip and helps to resolve the coincidence problem.For reasonable parameters,the deceleration parameter is well consistent with current observations.The original semi-holographic model is extended and it also suggests that the concordance model may be reconstructed from the semi-holographic idea.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10778710 and 10875171)
文摘Astrodynamical space test of relativity using optical devices optimized for gravitation wave detection （ASTROD- GW） is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection sensitivity is shifted 52 times toward larger wavelength compared with that of laser interferometer space antenna （LISA）. The mission orbits of the three spacecrafts forming a nearly equilateral triangular array are chosen to be near the Sun–Earth Lagrange points L3, L4, and L5. The three spacecrafts range interferometrically with one another with an arm length of about 260 million kilometers. In order to attain the required sensitivity for ASTROD-GW, laser frequency noise must be suppressed to below the secondary noises such as the optical path noise, acceleration noise, etc. For suppressing laser frequency noise, we need to use time delay interferometry （TDI） to match the two different optical paths （times of travel）. Since planets and other solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the TDI, we simulate the time delay numerically using CGC 2.7 （here, CGC stands for center for gravitation and cosmology） ephemeris framework. To conform to the ASTROD-GW planning, we work out a set of 20-year optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and calculate the differences in optical path in the first and second generation TDIs separately for one-detector case. In our optimized mission orbits of 20 years, changes of arm lengths are less than 0.0003 AU; the relative Doppler velocities are all less than 3m/s. All the second generation TDI for one-detector case satisfies the ASTROD-GW requirement.
基金Supported by the National Nature Science Foundation of China under Grant No 10473007
文摘We study the quasinormal modes （QNMs） for stringy black holes. By using numerical calculation, the relations between the QNMs and the parameters of black holes are minutely shown. For （1＋1）-dimensional stringy black hole, the real part of the quasinormal frequency increases and the imaginary part of the quasinormal frequency decreases as the mass of the black hole increases. Furthermore, the dependence of the QNMs on the charge of the black hole and the flatness parameter is also illustrated. For （1＋3）-dimensional stringy black hole, increasing either the event horizon or the multipole index, the real part of the quasinormal frequency decreases. The imaginary part of the quasinormal frequency increases no matter whether the event horizon is increased or the multipole index is decreased.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP)under Grant No 200931271104Shanghai Municipal Pujiang Foundation under Grant No 10PJ1408100.
文摘A new cosmological model based on the de Sitter gravity is investigated by dynamical analysis and numerical discussions.Via some transformations,the evolution equations of this model can form an autonomous system with 8 physical critical points.Among these critical points there exist one positive attractor and one negative attractor.The positive attractor describes the asymptotic behavior of late-time universe,which indicates that the universe will enter the exponential expansion phase,finally.Some numerical calculations are also carried out,which convince us of this conclusion derived from the dynamical analysis.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10747155,11205131,11075106,11005164,11175270 and 10935013the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,Shanghai Municipal Pujiang under Grant No 10PJ1408100+1 种基金CQ CSTC under Grant No 2010BB0408the Argonne National Laboratory.
文摘We study the semi-holographic idea in the context of decaying dark components.The energy flow between dark energy and the compensating dark matter is thermodynamically generalized to involve a particle number variable dark component with non-zero chemical potential.It is found that,unlike the original semi-holographic model,no cosmological constant is needed for a dynamical evolution of the universe.A transient phantom phase appears while a non-trivial dark energy-dark matter scaling solution stays at a later time,which evades the big-rip and helps to resolve the coincidence problem.For reasonable parameters,the deceleration parameter is well consistent with current observations.The original semi-holographic model is extended and it also suggests that the concordance model may be reconstructed from the semi-holographic idea.
