Studies in History and Philosophy of Modern Physics最新文献

The paper re-examines Nordström's scalar theory of gravity (NG) – arguably the most convincing relativistic theory of gravity before the advent of General Relativity. It exists in two different formulations. In Nordström's original one (1913), NG appears to describe a scalar gravitational field on Minkowski spacetime. In Einstein and Fokker’s (1914) version, NG seems to be a spacetime theory: It reconceptualises gravitational effects as manifestations of non-Minkowskian inertial structure. Both variants of NG give rise to three contradictory verdicts on the status and validity of fundamental principles: the Weak Equivalence Principle, the existence of gravitational energy, and energy conservation. Given the putative equivalence of both variants of NG, this ambiguity seems paradoxical to the spacetime realist. I'll proffer a resolution from the perspective of integrable Weyl geometry: The paradoxes rest on the failure to recognise a more apposite spacetime setting for NG.

The current state of particle physics is conflicting. One has a marvellously working theory, the Standard Model, that leaves many questions open. This tension has led to a variegated landscape of models of physics beyond the Standard Model that is guided by epistemic and pragmatic values of model preference. Whereas these preferences are shared by experimentalists and theorists, their use of models within research practice differs. Experimentalists focus on event signatures that have many-to-many relations to models. We argue that physicists’ three-pronged approach distinguishing raw data, signatures, and models resembles the analysis of Bogen and Woodward, establishing the autonomy of phenomena. Using signatures opens the door for explorative experimentation, which becomes crucial for managing the uncertainty about the direction of particle physics that has emerged after the discovery of the Higgs boson.

The multiple detections of gravitational waves by LIGO (the Laser Interferometer Gravitational-Wave Observatory), operated by Caltech and MIT, have been acclaimed as confirming Einstein's prediction, a century ago, that gravitational waves propagating as ripples in spacetime would be detected. Yunes and Pretorius (2009) investigate whether LIGO's template-based searches encode fundamental assumptions, especially the assumption that the background theory of general relativity is an accurate description of the phenomena detected in the search. They construct the parametrized post-Einsteinian (ppE) framework in response, which broadens those assumptions and allows for wider testing under more flexible assumptions. Their methods are consistent with work on confirmation and testing found in Carnap (1936), Hempel (1969), and Stein (1992, 1994), with the following principles in common: that confirmation is distinct from testing, and that, counterintuitively, revising a theory's formal basis can make it more broadly empirically testable. These views encourage a method according to which theories can be made abstract, to define families of general structures for the purpose of testing. With the development of the ppE framework and related approaches, multi-messenger astronomy is a catalyst for deep reasoning about the limits and potential of the theoretical framework of general relativity.

According to the Standard Model of particle physics, some gauge transformations are physical symmetries. That is, they are mathematical transformations that relate representatives of distinct physical states of affairs. This is at odds with the standard philosophical position according to which gauge transformations are an eliminable redundancy in a gauge theory's representational framework. In this paper I defend the Standard Model's treatment of gauge from an objection due to Richard Healey. If we follow the Standard Model in taking some gauge transformations to be physical symmetries then we face the “strong CP problem”, but if we adopt the standard philosophical position on gauge then the strong CP problem dissolves. Healey offers this as a reason in favor of the standard philosophical view. However, as I argue here, following Healey's recommendation gives a theory that makes bad empirical predictions.

This is one of a pair of papers that give a historical-cum-philosophical analysis of the endeavour to understand black hole entropy as a statistical mechanical entropy obtained by counting string-theoretic microstates. Both papers focus on Andrew Strominger and Cumrun Vafa's ground-breaking 1996 calculation, which analysed the black hole in terms of D-branes. The first paper gives a conceptual analysis of the Strominger-Vafa argument, and of several research efforts that it engendered. In this paper, we assess whether the black hole should be considered as emergent from the d-brane system, particularly in light of the role that duality plays in the argument. We further identify uses of the quantum-to-classical correspondence principle in string theory discussions of black holes, and compare these to the heuristics of earlier efforts in theory construction, in particular those of the old quantum theory.

This paper develops an approach to the interpretation of quantum mechanics inspired by the philosophy of Howard Stein. Taking up Stein’s (1994) call to schematize the observer and the observation, I introduce a class of observables called ‘sensibles’ which provide a means to assign probabilities to an observer's experiences of experimental phenomena. In particular, sensibles provide an assignment of probabilities to an event space that, while satisfying the demands of probability theory, also allows for an interpretation of these events as occurring at definite space-time regions. On this understanding, the experimental events to which probabilities are ascribed are conditional occurrences—types of events which occur at a definite location in a specific experimental context. This proposal differs from dynamical collapse theories such as GRWf since these sensibles are genuine quantum observables arising from the unitary dynamics of the theory. I conclude with some remarks on the import of Stein's philosophy for the measurement problem.

In this paper, ‘novelty’ is explored through a recent historical episode from high energy experimental physics to offer an understanding of novelty as disruption. I call this the ‘750 GeV episode’, an episode where two Large Hadron Collider (LHC) experiments, CMS and ATLAS, each independently observed indications of a new resonance at approximately 750 GeV. With further data collection, the initial excess was determined to be a statistical fluctuation. The approach taken, in the analysis of interviews conducted with physicists who were involved in the ‘750 GeV episode’, is to consider novelty as a valued difference. Following this conceptually driven approach, disambiguate between several notions of novelty through the identification of varied differences. This disambiguation is achieved through exploring differences expressed in comparison to varied expressions of the standard model, and through exploring varied ‘types’ of difference (properties and entities) to introduce disruptive exploratory experimentation, a complementary understanding ‘exploratory experimentation’ (Elliott, 2007; Steinle, 1997, 2002). I show that the kinds of novelty framed as most valuable are those that violate expectations and are difficult to incorporate into the existing structures of knowledge. In such instances, disruption to the existing ontology or ways of knowing is valued. This positive appraisal of disruption, and contradiction over confirmation, is considered in the recent context of high-energy physics, where several physicists have claimed that there is a lack of promising directions for the future, or even that the field is in a ‘crisis’. I show that the role of disruption explains the differences between the differing notions of novelty. Furthermore, I show that the positive appraisal of disruption is based on forward looking assessments of future fertility, or heuristic appraisal (Nickles, 1989, 2006). Within the context of concerns of a lack of available promising future directions, disruption becomes a generator of alternative futures.

We start by surveying the history of the idea of a fundamental conservation law and briefly examine the role conservation laws play in different classical contexts. In such contexts we find conservation laws to be useful, but often not essential. Next we consider the quantum setting, where the conceptual problems of the standard formalism obstruct a rigorous analysis of the issue. We then analyze the fate of energy conservation within the various viable paths to address such conceptual problems; in all cases we find no satisfactory way to define a (useful) notion of energy that is generically conserved. Finally, we focus on the implications of this for the semiclassical gravity program and conclude that Einstein's equations cannot be said to always hold.