Dark matter,the Equivalence Principle and modified gravity

Dark matter (DM) is an essential ingredient of the present Standard Cosmological Model, according to which only 5% of the mass/energy content of our universe is made of ordinary matter. In recent times, it has been argued that certain cases of gravitational lensing represent a new type of evidence for the existence of DM. In a recent paper, Peter Kosso attempts to substantiate that claim. His argument is that, although in such cases DM is only detected by its gravitational effects, gravitational lensing is a direct consequence of Einstein's Equivalence Principle (EEP) and therefore the complete gravitational theory is not needed in order to derive such lensing effects. In this paper I critically examine Kosso's argument: I confront the notion of empirical evidence involved in the discussion and argue that EEP does not have enough power by itself to sustain the claim that gravitational lensing in the Bullet Cluster constitutes evidence for the DM Hypothesis. As a consequence of this, it is necessary to examine the details of alternative theories of gravity to decide whether certain empirical situations are indeed evidence for the existence of DM. It may well be correct that gravitational lensing does constitute evidence for the DM Hypothesis—at present it is controversial whether the proposed modifications of gravitation all need DM to account for the phenomenon of gravitational lensing and if so, of which kind—but this will not be a direct consequence of EEP.     

The Equivalence Myth of Quntum Mechanics (Addendum)

This addendum non-trivially strengthens one of the six claims of my two-part paper ‘The Equivalence Myth of Quantum Mechanics’, published in this journal in 1997.     

分形空间中力学规律的适应性原理与标度不变性原理

本文应重整化群的参数空间变换和标度空间变换的方法证明了分形空间的力学规律的适应性原理和标度不变性原理。从空间变换的角度讲．从分形空间的物理规律到欧式空间的物理规律变换就是标度不变性的变换,从欧氏空间的物理规律到分形空间的物理规律变换就是一个适应性变换。其推论是分形空间的能量守恒定律、力的合成及其位移的合成在分形空间上保持形式不变。同时,Carpinteri的分形空间的空间维数关系利用重整化方法获得证明,即分形空间的体积的维数溢出量等于分形空间的截线和截面的维数溢出量之和。     

ITS指挥系统的"满意优化原则"

本文运用满意优化的基本理论,提出了ＩＴＳ指挥系统的一般满意优化原则,给出了城市交通主列车运行调度指挥满意优化原则的基本内容及相关的评价指标。     

景区开发原则与旅游发展对策

旅游业是综合性的新兴产业,也是四川省着力培育的支柱产业之一.它关联性大,发展迅速,投入产出高,市场扩张能力强,可提供大量就业机会,能有效带动产业结构的调整和升级,促进区域经济的快速发展.四川有丰富的旅游资源,如何将资源优势转化为经济优势,是值得认真研究的重大课题.     

Principle or constructive relativity

Appealing to Albert Einstein's distinction between principle and constructive theories, Harvey Brown has argued for an interpretation of the theory of relativity as a dynamic and constructive theory. Brown's view has been challenged by Michel Janssen and in this paper I investigate their dispute. I argue that their disagreement appears larger than it actually is due to the two frameworks used by Brown and Janssen to express their respective views: Brown's appeal to Einstein's principle–constructive distinction and Janssen's framing of the disagreement as one over the question whether relativity provides a kinematic or a dynamic constraint. I appeal to a distinction between types of theories drawn by H. A. Lorentz two decades before Einstein's distinction to argue that Einstein's distinction represents a false dichotomy. I argue further that the disagreement concerning the kinematics–dynamics distinction is a disagreement about labels but not about substance. There remains a genuine disagreement over the explanatory role of spacetime geometry and here I agree with Brown arguing that Janssen sees a pressing need for an explanation of Lorentz invariance where no further explanation is needed.     

Theory (In-)Equivalence and conventionalism in f(R) gravity

f(R) Gravity is the most natural extension of General Relativity within Riemannian Geometry. Due to (inter alia) its potential capacity for a unified treatment of early and late-time cosmic expansion, it has enjoyed recent attention in astrophysics and cosmology. I critically examine three inter-related claims found in the pertinent physics literature, of general interest to the philosopher of science. 1. f(R) Gravity is equivalent to a particular Brans-Dicke Theory. 2. The spacetime geometry underpinning f(R) Gravity has substantial conventional elements. 3. f(R) Gravity is an instance of a theory in which the distinction between matter and spacetime is conventional. Whilst the first claim can be vindicated in precise terms, the remaining two claims, I submit, are unwarranted – at least for the reasons usually adduced. On different grounds, though, the case for conventionalism about spacetime geometry in f(R) Gravity (as well as General Relativity) turns out to be considerably stronger.     

Quantum Mechanics as a Principle Theory

I show how quantum mechanics, like the theory of relativity, can be understood as a ‘principle theory’ in Einstein's sense, and I use this notion to explore the approach to the problem of interpretation developed in my book Interpreting the Quantum World.     

简易隔音原理与模型的研究

声源的振动在介质中传播产生声压形成声波,喇叭头(见图1)振膜受到声压的作用带动附在其上的线圈在磁铁的磁场中振动,将线圈接入闭合通路产生电流,据楞次定律,磁铁对电流产生的安培力会阻碍其运动,供给线圈同向的适当大小的电流.使安培力增大到足以抵消声压对振膜的作用,就可起到隔音的效果.实验中是用另一个特性相同的喇叭头来提供这种电流的.电流大小的调节可通过音频放大电路来实现.通过以上方法.就可得到一个对特定频率范围有减音效果的模型.     

A probabilistic “New Principle” of the 19th century

We discuss the evolution of an idea which contains, within the setting of an urn model, the notion of a martingale. The idea is to be found inPoisson (1837) but its main proponent isCatalan in a series of papers beginning in 1841, in partial ignorance ofPoisson's work. The usualBayesian coloration is present. A letter fromBienaymé of 1878, possibly his last, toCatalan elucidates the origin of the idea, and illustrates the personal relations of French probabilists at the time.     

States of ignorance and ignorance of states: Examining the Quantum Principal Principle

Earman (2018) has recently argued that the Principal Principle, a principle of rationality connecting objective chance and credence, is a theorem of quantum probability theory. This paper critiques Earman's argument, while also offering a positive proposal for how to understand the status of the Principal Principle in quantum probability theory.     

Mecanum三轮多向行走系统结构与运动原理

常规Mecanum轮一般用于组成四轮全方位系统。将三个完全相同的常规Mecnum轮放置在等边三角形的三个顶点,能构成一种具有实用价值的多向行走系统。该系统不需转向轮或转向机构,仪利用3个轮子旋转速度大小和旋向组合实现平面上一个绕车身中心的定轴旋转、三个沿车身三角形对角线的直线运动。并给出了该系统的结构图,分析了系统实现上述运动的运动学原理。     

钻孔局部壁面应力解除法(BWSRM)的原理及其在锦屏二级水电站工程中的初步应用

岩体初始地应力问题的研究在岩石力学与工程领域具有重要意义.作为地质体组成部分的岩体与其他材料明显不同之处之一就是其内部赋存有地应力状态,了解地壳某一局部区域地质岩体残余至今的地应力状态是一项极为复杂而又十分重要的研究课题.对地壳应力状态的认识虽然总体上有一些规律可寻,但主要手段还是靠现场原位的地应力实测.简要评述了目前普遍采用的三维地应力测量方法及其不足.提出了钻孔局部壁面应力解除法(BWSRM)三维地应力测量原理及其具体实施方案,研制了基于BWSRM法为原理的地应力测井机器人,并将其初步应用于锦屏二级水电站工地埋深达2430m处的地应力实测工作,验证了BWSRM法地应力测量原理的可行性和合理性.BWSRM法与测井机器人在地应力测井工作中的推广和应用具有十分广阔的前景.     

第二次现代化理论与中国现代化

第二次现代化理论认为：人类社会的发展可分为四个,即原始,农业社会,工业社会和知识社会,第一个阶段又分为四个时期,即起步期,发展期,成就期和过渡期;从农业社会向工业社会的转移过程是第一次现代化,从工业社会向知识社会的转移过程是第二次现代化。     

生物信息学的现状与展望

本文阐述了生物信息学产生的背景,生物学数据库,生物信息学的主要研究内容,与生物信息学关系密切的数学和计算机科学技术领域,生物信息学产业等内容,展望了其未来并提出了若干在我国发展生物信息学的建议。着重指出,理解大量生物学数据所包括的生物学意义已成为后基因组时代极其重要的课题。生物信息学的作用将日益重要。有理由认为,今日生物学数据的巨大积累将导致重大生物学规律的发现。生物信息学的发展在国内、外基本上都处在起步阶段。因此,这是我国生物学赶超世界先进水平的一个百年一遇的极好机会。