A search for a problem free cosmology

We explore features of a nonminimally coupled theory of scalar fields with an effective potential that supports non topological soliton solutions. It is suggested that a problem free cosmology results.     

香山绝对点周围的局部地壳变形及其对重力测量结果的影响

为了监视北京地区的地壳稳定性，北京测绘院对10多个基岩点和北京市区进行了多次沉降观测，结果表明香山点近10多年来高程变化只有几毫米，其重力效应可略而不计，但测点东北和东南方有两个较大的下沉区。用线积分法计算了两个局部沉降的重力效应，在沉降区中心其影响可达0.38μms^-2，但对香山点的重力效应非常小，完全可以忽略。因此得出如下结论：香山点观测到的重力变化不是地壳变形引起的。     

北京大灰厂试验场重力变化特征及其解释

介绍了北京大灰厂试验场（简称京西试验场）的概况，对１９９３年３月以来重力重复观测资料进行了处理。计算了各期重力观测精度，结果显示１９９３年３月～１９９５年５月京西试验场存在一定重力变化。采用给定的模型反演了八宝山断层介质的密度变化，认为断层破碎带介质密度的变化可能是引起地表重力变化的主要因素     

Geopotential from space techniques

The monitoring of the perturbed motion of artificial satellites since the 1960's has provided a valuable resource for improved activities in geodesy. These observations and the improved geodetic techniques they fostered have provided an unparalleled means for studying both the gravity field and the Earth's shape. In this paper, we will review the various determinations of the Earth's gravity field produced at many research centers over the years from space techniques. The specific methods which have been used to measure our planet, such as satellite altimetry and satellite orbital perturbation analyses (over short and long periods of time), will be compared.     

用区域重力资料确定的华北地台南缘地缝合线及其地质意义

利用１∶２０万区域重力资料，结合航磁，电磁测深、遥感、天然地震等丰富的地质、地球物理资料，根据断裂的地质、地球物理标志，在华北地台南缘发现并确定了控制火山喷发的裂隙—中心式古火山通道，即隐伏的北西西向的上戈—铁炉坪—付店超壳断裂带。该断裂属华北地台南缘不同时代、不同性质的近东西向的地缝合线。研究认为：该断裂及其次级断裂不仅是重要的长期多次活动的控岩、导矿和容矿构造，而且也为矿床的多次改造、叠加和再富集提供了热源。它的发现，对重新认识豫西地区大地构造的演化特征，建立新的成矿模式，拓宽该区的找矿前景具有重要意义。     

Energy of a Stringy Charged Black Hole in the Teleparallel Gravity

We use the teleparallel geometry analog of the Møller energy-momentum complex to calculate the energy distribution (due to matter plus field including gravity) of a charged black hole solution in heterotic string theory. We find the same energy distribution as obtained by Gad who investigated the same problem by using the Møller energy-momentum complex in general relativity. The total energy depends on the black hole mass M and charge Q. The energy obtained is also independent of the teleparallel dimensionless coupling constant, which means that it is valid not only in the teleparallel equivalent of general relativity, but also in any teleparallel model. Furthermore, our results also sustains (a) the importance of the energy-momentum definitions in the evaluation of the energy distribution of a given spacetime and (b) the viewpoint of Lessner that the Møller energy-momentum complex is a powerful concept of energy and momentum.     

Synchrotron radiation from the Crab Nebula discriminates between models of space–time foam

It has been argued by Jacobson, Liberati and Mattingly that synchrotron radiation from the Crab Nebula imposes a stringent constraint on any modification of the dispersion relations of the electron that might be induced by quantum gravity. We supplement their analysis by deriving the spectrum of synchrotron radiation from the coupling of an electrically charged particle to an external magnetic fields in the presence of quantum-gravity effects of the general form (E/M_QG). We find that the synchrotron constraint from the Crab Nebula practically excludes 1.74 for M_QGm_P=1.2×10¹⁹ GeV. On the other hand, this analysis does not constrain any modification of the dispersion relation of the photon that might be induced by quantum gravity. We point out that such quantum-gravity effects need not obey the equivalence principle, a point exemplified by the Liouville-string D-particle model of space–time foam. This model suggests a linear modification of the dispersion relation for the photon, but not for the electron, and hence is compatible with known constraints from the Crab Nebula and elsewhere.     

TOWARDS AN INTEGRATED SCIENTIFIC AND SOCIAL CASE FOR HUMAN SPACE EXPLORATION

I will argue that an ambitious programme of human space exploration, involving a return to the Moon, and eventually human missions to Mars, will add greatly to human knowledge. Gathering such knowledge is the primary aim of science, but science’s compartmentalisation into isolated academic disciplines tends to obscure the overall strength of the scientific case. Any consideration of the scientific arguments for human space exploration must therefore take a holistic view, and integrate the potential benefits over the entire spectrum of human knowledge. Moreover, science is only one thread in a much larger overall case for human space exploration. Other threads include economic, industrial, educational, geopolitical and cultural benefits. Any responsibly formulated public space policy must weigh all of these factors before deciding whether or not an investment in human space activities is scientifically and socially desirable.     

月球重力场对绕月低轨卫星的长期影响

从解析形式出发,利用月球重力场模型JGL165P1,分析了月球重力场(带谐项)对绕月低轨卫星的长期影响。为了减少计算误差,保证计算精度,在分析解中使用循环公式来计算倾角函数。结果指出对于一个高度为100km的极月轨道卫星,冻结轨道存在的可能性不大,但是当轨道倾角在i=90°附近或者高度再高一些,则有可能存在冻结轨道;对于100km高的初始圆轨道,卫星在无控的情况下半年内将会坠落到月球表面,如果高度增加到200km,则不进行轨道控制也不会坠落到月面上。利用仿真软件GEODYN解算出来的结果证实了上述结论。