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The goal of this article is to analyze the role of convention in interpreting physical theories—in particular, how the distinction between the conventional and the nonconventional interacts with judgments of equivalence. We will begin with a discussion of what, if anything, distinguishes those statements of a theory that might be dubbed "conventions." This will lead us to consider the conventions that are not themselves part of a theory's content but are rather applied to the theory in interpreting it. Finally, we will consider the idea that what conventions to adopt might, itself, be regarded as a matter of convention. [ABSTRACT FROM AUTHOR]

There are well-known problems associated with the idea of (local) gravitational energy in general relativity. We offer a new perspective on those problems by comparison with Newtonian gravitation, and particularly geometrized Newtonian gravitation (i.e., Newton–Cartan theory). We show that there is a natural candidate for the energy density of a Newtonian gravitational field. But we observe that this quantity is gauge dependent, and that it cannot be defined in the geometrized (gauge-free) theory without introducing further structure. We then address a potential response by showing that there is an analogue to the Weyl tensor in geometrized Newtonian gravitation.

This article establishes and addresses opportunities for ethics integration into Machine-learning (ML) courses. Following a survey of the history of computing ethics and the current need for ethical consideration within ML, we consider the current state of ML ethics education via an exploratory analysis of course syllabi in computing programs. The results reveal that though ethics is part of the overall educational landscape in these programs, it is not frequently a part of core technical ML courses. To help address this gap, we offer a preliminary framework, developed via a systematic literature review, of relevant ethics questions that should be addressed within an ML project. A pilot study with 85 students confirms that this framework helped them identify and articulate key ethical considerations within their ML projects. Building from this work, we also provide three example ML course modules that bring ethical thinking directly into learning core ML content. Collectively, this research demonstrates: (1) the need for ethics to be taught as integrated within ML coursework, (2) a structured set of questions useful for identifying and addressing potential issues within an ML project, and (3) novel course models that provide examples for how to practically teach ML ethics without sacrificing core course content. An additional by-product of this research is the collection and integration of recent publications in the emerging field of ML ethics education.

How may we characterize the intrinsic structure of physical quantities such as mass, length, or electric charge? This article shows that group-theoretic methods—specifically, the notion of a free and transitive group action—provide an elegant way of characterizing the structure of scalar quantities, and uses this to give an intrinsic treatment of vector quantities. It also gives a general account of how different scalar or vector quantities may be algebraically combined with one another. Finally, it uses this apparatus to give a simple intrinsic treatment of Newtonian gravitation. [ABSTRACT FROM AUTHOR]

If categorical equivalence is a good criterion of theoretical equivalence, then it would seem that if some class of mathematical structures is represented as a category, then any other class of structures categorically equivalent to it will have the same representational capacities. Hudetz (2019 a) has presented an apparent counterexample to this claim; in this note, I argue that the counterexample fails. [ABSTRACT FROM AUTHOR]

Tomasz Bigaj’s new book is an authoritative and comprehensive discussion of recent issues concerning the means and metaphysical implications of individuating identical quantum particles. This review briefly summarises the book’s contributions and considers some of its implications for the debate over indiscernibility in quantum mechanics. [ABSTRACT FROM AUTHOR]

Week 1: Introduction to the epistemology of spacetime What is the epistemology of spacetime? In this Teaching and Learning Guide, we chart a course through this literature, and also provide a sample syllabus for how the epistemology of spacetime might be taught. An excellent account of the Problem of Space and how it "fathered" three major schools of philosophy of geometry that heavily inspired our own mode of presentation of the epistemology of spacetime. SAMPLE SYLLABUS In this section, we provide a sample syllabus for how the key issues in the epistemology of spacetime might be taught in one course. [Extracted from the article]

How is it that the basic structures of space and time come to manifest themselves in physical theories and theorising, and in our empirical experience of the world? This question is central to an important field of the philosophy of physics: the epistemology of spacetime. In this article, we survey systematically the various responses which have been offered to this question, highlighting little‐explored connections and open research questions. [ABSTRACT FROM AUTHOR]

This is an essay about general covariance, and what it says (or doesn't say) about spacetime structure. After outlining a version of the dynamical approach to spacetime theories, and how it struggles to deal with generally covariant theories, I argue that we should think about the symmetry structure of spacetime rather differently in generally-covariant theories compared to non-generally-covariant theories: namely, as a form of internal rather than external symmetry structure. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "On translating between logics."

Urban agriculture is a contested issue in the larger South African debate on urban poverty alleviation. This paper investigates the economic viability of urban agriculture and informs the debate on the optimal use of open space in Khayelitsha. It compares the economic performance of the Scaga community garden in the low-income township Khayelitsha, predicted in a 1998 study by Fermont et al., with empirical results of a similar study by Fleming in 2003. It concludes that urban agriculture in Khayelitsha is potentially economically viable, subject to certain conditions being satisfied. However, as a land use, urban agriculture competes with housing, ecological corridors, the stormwater management system and nature areas and reserves. [ABSTRACT FROM AUTHOR]

Promulgation of the Republic of South Africa Constitution Act of 1983, the inauguration of eleven Black Town Councils in January 1984, and subsequent legislation regarding third tier government brings immediacy to the subject of the geographic implications of political autonomy and the control of urban finance in South Africa. This paper reviews recent changes affecting local government under the new political dispensation and discusses some important geographic implications of these changes. In particular it advances the argument that the logic of current legislation directed towards the exercise of municipal autonomy by individual ethnic groups can be extended to presage fundamental change in national social and political structures of a sort not envisaged by the architects of the present constitution. In short local autonomy could become an instrument in the dialectics of political change in South Africa. [ABSTRACT FROM PUBLISHER]

Four sustainable materials including a recycled polypropylene blend, polybutylene adipate terephthalate, and two grades of polylactic acid are compared to a reference isotactic polypropylene. Tensile specimens were produced using a two-cavity, hot runner mold with fully automatic cycles per standard industrial practices to investigate the effect of melt temperature, injection velocity, cycle time, and screw speed on the mechanical properties. Multiple regression and principal component analyses were performed for each of the materials. Results indicated that all the materials were readily processed using a hot runner, and the mechanical properties exhibited minimal variation. To the extent that losses in mechanical properties were observed, the results indicated that the losses were correlated with thermal degradation as independently characterized by thermal gravimetric analysis. Such losses can be minimized by reducing melt temperature and cycle time, leading to a reduction of the environmental impact of injection molding processes. [ABSTRACT FROM AUTHOR]

In the following paper, we discuss new methods to trap and manipulate airborne liquid aerosol droplets. We discuss the single gradient force trapping of water aerosols in the 2-14 micron diameter range using both 532 nm and 1064 nm light, as well as the holographic optical trapping of arrays of aerosols. Using this holographic technique, we are able to show controlled aerosol coagulation. We also discuss two techniques based on the radiation pressure trapping of aerosols, namely the dual beam fibre trap and the controlled guiding of aerosols using Bessel beams. We conclude with a discussion of new topics for study based upon these techniques and some possible applications.