Why history matters to philosophy of physics

Naturalized metaphysics remains the default presupposition of much contemporary philosophy of physics. As metaphysics is supposed to concern the general structure of reality, so scientific naturalism draws upon our best physical theories to attempt to answer the foundational question “par excellence ” viz., “how could the world possibly be the way this theory says it is?” A particular case study, Hilbert's attempt to analyze and explain a seeming “pre-established harmony” between mind and nature, is offered as a salutary reminder that naturalism's ready inference from physical theory to ontology may be too quick.     

Klein-Weyl's program and the ontology of gauge and quantum systems

We distinguish two orientations in Weyl's analysis of the fundamental role played by the notion of symmetry in physics, namely an orientation inspired by Klein's Erlangen program and a phenomenological-transcendental orientation. By privileging the former to the detriment of the latter, we sketch a group(oid)-theoretical program—that we call the Klein-Weyl program—for the interpretation of both gauge theories and quantum mechanics in a single conceptual framework. This program is based on Weyl's notion of a “structure-endowed entity” equipped with a “group of automorphisms”. First, we analyze what Weyl calls the “problem of relativity” in the frameworks provided by special relativity, general relativity, and Yang-Mills theories. We argue that both general relativity and Yang-Mills theories can be understood in terms of a localization of Klein's Erlangen program: while the latter describes the group-theoretical automorphisms of a single structure (such as homogenous geometries), local gauge symmetries and the corresponding gauge fields (Ehresmann connections) can be naturally understood in terms of the groupoid-theoretical isomorphisms in a family of identical structures. Second, we argue that quantum mechanics can be understood in terms of a linearization of Klein's Erlangen program. This stance leads us to an interpretation of the fact that quantum numbers are “indices characterizing representations of groups” ((Weyl, 1931a), p.xxi) in terms of a correspondence between the ontological categories of identity and determinateness.     

Interpreting cosmic no hair theorems: Is fatalism about the far future of expanding cosmological models unavoidable?

It may be tempting to interpret cosmic no hair theorems (establishing that, under certain conditions, a cosmological model with accelerating expansion approaches de Sitter metric in the future) as implying a form of fatalism about a future state of the universe. In this note I explore (rather general) philosophical and (more concrete) physical reasons to resist such temptation. There are good reasons to think that (even locally) futures of expanding cosmological models may be unlike de Sitter.     

Coincidence and reproducibility in the EHT black hole experiment

This paper discusses some philosophical aspects related to the recent publication of the experimental results of the 2017 black hole experiment, namely the first image of the supermassive black hole at the center of galaxy M87. In this paper I present a philosophical analysis of the 2017 Event Horizon Telescope (EHT) black hole experiment. I first present Hacking's philosophy of experimentation. Hacking gives his taxonomy of elements of laboratory science and distinguishes a list of elements. I show that the EHT experiment conforms to major elements from Hacking's list. I then describe with the help of Galison's Philosophy of the Shadow how the EHT Collaboration created the famous black hole image. Galison outlines three stages for the reconstruction of the black hole image: Socio-Epistemology, Mechanical Objectivity, after which there is an additional Socio-Epistemology stage. I subsequently present my own interpretation of the reconstruction of the black hole image and I discuss model fitting to data. I suggest that the main method used by the EHT Collaboration to assure trust in the results of the EHT experiment is what philosophers call the Argument from Coincidence. I show that using this method for the above purpose is problematic. I present two versions of the Argument from Coincidence: Hacking's Coincidence and Cartwright's Reproducibility by which I analyse the EHT experiment. The same estimation of the mass of the black hole is reproduced in four different procedures. The EHT Collaboration concludes: the value we have converged upon is robust. I analyse the mass measurements of the black hole with the help of Cartwright's notion of robustness. I show that the EHT Collaboration construe Coincidence/Reproducibility as Technological Agnosticism and I contrast this interpretation with van Fraassen's scientific agnosticism.     

Fantastic Beasts and where (not) to find them: Local gravitational energy and energy conservation in general relativity

This paper critically examines energy-momentum conservation and local (differential) notions of gravitational energy in General Relativity (GR). On the one hand, I argue that energy-momentum of matter is indeed locally (differentially) conserved: Physical matter energy-momentum 4-currents possess no genuine sinks/sources. On the other hand, global (integral) energy-momentum conservation is contingent on spacetime symmetries. Local gravitational energy-momentum is found to be a supererogatory notion. Various explicit proposals for local gravitational energy-momentum are investigated and found wanting. Besides pseudotensors, the proposals considered include those of Lorentz and Levi-Civita, Pitts and Baker. It is concluded that the ontological commitment we ought to have towards gravitational energy in GR mimics the natural anti-realism/eliminativism towards apparent forces in Newtonian Mechanics.     

宇宙年龄和宇宙物质密度

根据爱因斯坦广义相对论,时空弯曲,宇宙是有限的。现在已被主流物理学家普遍接受的是标准宇宙论,按标准宇宙论经过严格的数学推导,演算得到了宇宙的年龄、宇宙物质密度。作者根据广大天体物理工作者认可的观察数据和结论,通过初等数学的计算,得到的结果大相径庭。根本没天体物工作者寻找的暗物质。     

3D激光扫描与岩体结构精细测量方法比较研究——以锦屏Ⅰ级水电站为例

与传统的工程地质勘察方法相比,3D激光扫描,是一种新兴的工程地质勘察方法,以速度快、精度高、完全非接触测量为显著特征,因而逐步得到广泛应用,并且有日渐替代前者的趋势.3D激光扫描是否将会替代传统地质勘察方法,一直是许多学者关心的问题.这次研究,以工程实践为基础,通过对2种方法本身特点的对比,以及二者所获得包括结构面迹长、间距、Jv和RQD等工程地质要素的相关性分析,文章得出了新的认识.概言之,这种新的认识体现在,3D激光扫描较传统的工程地质勘察方法,间距值与RQD值较高,结构面迹长值、Jv值较低.最终可知,2种方法各具优势与不足,都有其自身适用的工况,并且,二者互为补充;二者所获得的上述工程要素具有正相关性,或者同向变化趋势.研究结果,丰富了该领域的研究内容,不仅指导了工程应用,而且有一定的理论意义.     

关于正态分布的重要结论及注记

实际问题中的许多随机变量服从正态分布,正态分布在概率统计中起着非常重要的作用.从某考研资料中的一道例题出发,给出了关于函数的正态分布的一个结论的证明,使读者对正态分布的理论及实际问题有进一步的认识,进而能够把正态分布应用于解决实际问题中.     

物质场论

文章认为物质是以场的形式存在,并通过辐射时空波作用于其他物质。这种作用包括在文章中讨论的量子叠加原理和相对论中的时空相对性原理。     

对脉冲双星PSR1913＋16引力辐射计算的一个注解

本文在牛顿的万有引力定律与爱因斯坦的狭义相对论之间找到一个理论结合点,使质电类比更具理据,以此对陈永明的脉冲双星PSR1913＋16引力辐射的计算提供一个注解。