Matter wave explorer of gravity (MWXG)

In response to ESA’s Call for proposals of 5 March 2007 of the COSMIC VISION 2015–2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5·10^− 16 m/s² corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 10¹⁶. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In this proposal we present in detail the mission objectives and the technical aspects of the proposed mission.     

Simultaneous observations of a pair of kilohertz QPOs and a plausible 1860Hz QPO from an accreting neutron star system

We report an indication(3.22 σ)of ≈ 1860Hz quasi-periodic oscillations from a neutron star low-mass X-ray binary 4U 1636-536.If confirmed,this will be by far the highest frequency feature observed from an accreting neutron star system,and hence could be very useful in understanding such systems.This plausible timing feature was observed simultaneously with lower(≈ 585Hz)and upper(≈ 904Hz)kilohertz quasi-periodic oscillations.The two kilohertz quasi-periodic oscillation frequencies had a ratio of ≈ 1.5,and t...     

The first high-amplitude δ Scuti star in an eclipsing binary system

Consider radar ranging of a distant galaxy in a Friedman–Lemaître cosmological model. In this model the comoving coordinate of the galaxy is constant; hence, the equations of null geodesics for photons travelling to the distant galaxy and back imply Here, τ_e, τ_r and τ_o are, respectively, the times of emission, reflection and observation of the reflected photons, and a (τ) is the scalefactor. Since the Universe is expanding, a (τ) is a monotonically increasing function, so the return traveltime, τ_o−τ_r, must be greater than the forward traveltime, τ_r−τ_e. Clearly, space expands, and on their way back, the photons must travel a longer distance! This paper explains why this argument for the Expansion of Space (EoS) is wrong. We argue that, unlike the expansion of the cosmic substratum, the EoS is unobservable. We therefore propose to apply to it – just like to the ether – Ockham's razor.     

时间、距离、速度、红移基本物理概念的演变简史

为了尝试回答“我们能否观测到退行速度超过光速的星系”这一问题,重新考察了在牛顿物理学、狭义相对论、广义相对论和宇宙学中的时伺、距离、速度和红移等概念．揭开了一些错误观念的实质,发现只要摆脱狭义相对论先入为主的束缚,上述问题即可迎刃而解．强调了宇宙学并不是纯粹的广义相对论,而是该理论在服从宇宙学原理的条件下的一个特例,其中一系列基本物理概念都因此得到新的内涵。     

红色泥岩风化含砾粘土的抗剪强度参数与物理性质相关性研究

研究了巴东组红色泥岩风化含砾粘土的含水量、密度及粘粒含量与内聚力C、摩察角φ的关系。通过配制粒径小于10mm的含砾粘土,按不同的含水量、密度及粘粒含量进行了大量的室内样品实验,分析总结了试验数据的一些规律,得出了适用的经验公式。这些经验公式揭示了该土体的一些特性,同时,当测得土体的某些物性指标后,可以运用这些公式计算该类土体的抗剪强度参数。这样,可避免少量试验数据用于设计时的不可靠性。     

相对论效应及其对GPS技术的影响

本文根据相对论基本原理,系统地阐述了GPS中必须仔细考虑的几项主要的相对论效应,包括运动时钟的时间膨胀、引力频移以及地球自转引起的Sagnac效应等,并对相对论效应在GPS中的实际应用进行了定量分析和讨论。     

Super-Eddington accretion discs around Kerr black holes

We calculate the structure of the accretion disc around a rapidly rotating black hole with a super-Eddington accretion rate. The luminosity and height of the disc are reduced by the advection effect. In the case of large viscosity parameter, α>0.03, the accretion flow deviates strongly from thermodynamic equilibrium and overheats in the central region. With increasing accretion rate, the flow temperature steeply increases, reaches maximum, and then falls off. The maximum is achieved in the advection-dominated regime of accretion. The maximum temperature in the disc around a massive black hole of M =10⁸ M⊙ with α=0.3 is of order 3×10⁸ K. The discs with large accretion rates can emit X-rays in quasars as well as in galactic black hole candidates.     

Differential rotation of relativistic superfluid in neutron stars

It is shown how to set up a mathematically elegant and fully relativistic superfluid model that can provide a realistic approximation (neglecting small anisotropies due to crust solidity, magnetic fields, etc., but allowing for the regions with vortex pinning) of the global structure of a rotating neutron star, in terms of just two independently moving constituents. One of these represents the differentially rotating neutron superfluid, while the other part represents the combination of all the other ingredients, including the degenerate electrons, the superfluid protons in the core, and the ions in the crust, the electromagnetic interactions of which will tend to keep them locked together in a state of approximately rigid rotation. Order of magnitude estimates are provided for relevant parameters such as the resistive drag coefficient.     

粘性类土侵蚀强度量化研究

海洋动力作用下,粘性土内部粘结力与重力的联合作用使其冲刷侵蚀特性较为复杂。从侵蚀原理出发,利用粘结力仪进行侵蚀试验,探讨了粘性土临界侵蚀剪应力τ_c与土体物理力学性质之间的相关性,并提出中值粒径、粘粒含量、密度及抗剪强度与τ_c之间的计算关系式。同时通过侵蚀公式计算结果与试验结果比较,验证了试验结果的准确性。