Orbit optimization for ASTROD-GW and its time delay interferometry with two arms using CGC ephemeris

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.

Object Picture of Quasinormal Modes for Stringy Black Holes

我们为象线的黑洞学习伪正常模式(QNM ) 。由使用数字计算，在 QNM 和黑洞的参数之间的关系详细地被显示出。因为(1+1 ) 维的象线的黑洞，伪正常频率增加的真实部分和伪正常频率的想象的部分作为黑洞增加的团减少。而且，黑洞和平坦参数的费用上的 QNM 的依赖也被说明。为(1+3 ) 维的象线的黑洞，增加事件地平线或多极索引，伪正常频率的真实部分减少。增加不管事件地平线是否被增加的伪正常频率或多极索引的 Theimaginary 部分被减少。

Dynamics of quintessential inflation

In this paper, we study a realistic model of quintessential inflation with radiation and matter. By the analysis of the dynamical system and numerical work about the evolution of the equation of state and cosmic density parameter, we show that this model is a good match for the current astronomical observation. The conclusion we obtain is in favour of the model where the modular part of the complex field plays the role of the infiaton whereas the argument part is the quintessence field. Numerical calculation shows that a heteroclinic orbit （solution of the dynamical system） is interpolated between early-time de Sitter phase （an unstable critical point） and a late-time de Sitter attractor.

Cosmological Dynamics of de Sitter Gravity

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.

A Generalized Semi-Holographic Universe

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.

Fluctuation with dust of de Sitter ground state of scalar-tensor gravity

An exact de Sitter solution of scalar-tensor gravity is found in our recent work,in which the non-minimal coupling scalar is rolling along a non-constant potential.Based on this solution,a dust-filled FRW universe is explored in frame of scalar-tensor gravity in this article.The efective dark energy induced by the sole non-minimal scalar can be quintessence-like,phantom-like,and more significantly,can cross the phantom divide.The rich and varied properties of scalar-tensor gravity even with only one scalar is shown.