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Reassessing the strength of a class of Wigner's friend no-go theorems
Get PDFTwo recent, prominent theorems—the "no-go theorem for observer-independent facts" and the "Local Friendliness no-go theorem"—employ so-called extended Wigner's friend scenarios to try to impose novel, non-trivial constraints on the possible nature of physical reality. While the former is argued to entail that there can be no theory in which the results of Wigner and his friend can both be considered objective, the latter is said to place on reality stronger constraints than the Bell and Kochen-Specker theorems. Here, I conduct a thorough analysis of these theorems and show that they suffer from a list of shortcomings that question their validity and limit their strength. I conclude that the "no-go theorem for observer-independent facts" and the "Local Friendliness no-go theorem" fail to impose significant constraints on the nature of physical reality
Relational Primitivism about the Direction of Time
Get PDFPrimitivism about the direction of time is the thesis that the direction of time does not call for an explanation because it is a primitive posit in one’s ontology. In the literature, primitivism has in general come along with a substantival view of time according to which time is an independent substance. In this paper, we defend a new primitivist approach to the direction of time –relational primitivism. According to it, time is primitively directed because change is primitive. By relying on Leibnizian relationalism, we argue that a relational ontology of time must be able to distinguish between spatial relations and temporal relations to make sense of the distinction between variation and change. This distinction, however, requires the assumption of a primitive directionality of change, which ushers in the direction of time. Relational primitivism is an attractive view for those who want to avoid substantivalism about time but retain a primitive direction of time in a more parsimonious ontology
Whence the desire to close the Universe?
Get PDFThe geometry of the universe is today widely believed to be flat based on combined data obtained during the 2000s. Prior to this, the geometry of the universe was essentially unknown. However, within the relevant literature one finds claims indicating a strong preference for a (nearly) closed universe, based on philosophical and other "non-xperimental" reasons. The main aim of this article is to identify these reasons and assess the extent to which philosophical reasoning influenced the establishment of the dark matter hypothesis and the development of models for a closed universe. Building on groundwork laid by de Swart (2020), this study expands the discussion by (a) arguing that opinions on the geometry of the universe during the 1970s and 1980s were more divided than often assumed, (b) uncovering a lesser-known Machian argument for flat geometry proposed by Dennis Sciama, and (c) presenting a fine-tuning argument stemming from the 'coincidence problem' articulated by Robert Dicke. The study provides a nuanced perspective on how philosophical considerations contributed to shaping early views on cosmology and dark matter and highlights the significant role philosophical reasoning can play in guiding scientific inquiry in physics
What is active touch?
Get PDFWhat is active touch? A common conception of active touch gives a rough but rather intuitive sketch. That is, active touch can be understood as mainly object-oriented, controlled movement. While parts or the totality of this characterization is espoused by an important number of researchers on touch, I will argue that this conception faces important challenges when we pay close attention to each of its features. I hold that active touch should be considered as before all else purposive. This view has its roots in the active sensing literature in robotics but will be amended to give insight into human touch in the natural world
How Theoretical Terms Effectively Refer
Get PDFScientific realists with traditional semantic inclinations are often pressed to explain away the distinguished series of referential failures that seem to plague our best past science. As recent debates make it particularly vivid, a central challenge is to find a reliable and principled way to assess referential success at the time a theory is still a live concern. In this paper, I argue that this is best done in the case of physics by examining whether the putative referent of a term is specifiable within the limited domain delineated by the range of parameters over which the theory at stake is empirically accurate. I first implement this selective principle into a general account of reference, building on Stathis Psillos's works. Then, I show that this account offers a remarkably reliable basis to assess referential success before theory change in the case of effective theories. Finally, I briefly show that this account still works well with other physical examples and explain how it helps us to handle problematic cases in the history of physical sciences
Why Do We Want a Theory of Quantum Gravity?
Get PDFThe search for a new scientific theory is typically prompted by an encounter with something in the world that cannot be explained by current theories. This is not the case for the search for a theory of quantum gravity, which has been primarily motivated by theoretical and philosophical concerns. This Element introduces some of the motivations for seeking a theory of quantum gravity, with the aim of instigating a more critical perspective on how they are used in defining and constraining the theory sought. These motivations include unification, incompatibilities between general relativity and quantum field theory, consistency, singularity resolution, and results from black hole thermodynamics
Wave Function Collapse, Lorentz Invariance, and the Third Postulate of Relativity
Get PDFThe changes that quantum states undergo during measurement are both probabilistic and nonlocal. These two characteristics complement one another to insure compatibility with relativity and maintain conservation laws. Nonlocal entanglement relations provide a means to enforce conservation laws in a probabilistic theory, while the probabilistic nature of nonlocal effects prevents the superluminal transmission of information. In order to explain these measurement-induced changes in terms of fundamental physical processes it is necessary to take these two key characteristics into account. One way to do this is to modify the Schroedinger equation by adding stochastic, nonlinear terms. A number of such proposals have been made over the past few decades. A recently proposed equation based on the assumption that wave function collapse is induced by a sequence of correlating interactions of the kind that constitute measurements has been shown to maintain strict adherence to conservation laws in individual instances, and has also eliminated the need to introduce any new, ad hoc physical constants.
In this work it is shown that the stochastic modification to the Schroedinger equation is Lorentz invariant. It is further argued that the additional spacetime structure that it requires provides a way to implement the assumption that spacelike-separated operators (and measurements) commute, and that this assumption of local commutativity should be regarded as a third postulate of relativity
How Theory-laden are Observations of Black Holes?
Get PDFWe evaluate the roles general relativistic assumptions play in simulations used in recent observations of black holes including LIGO-Virgo and the Event Horizon Telescope. In both experiments simulations play an ampliative role, enabling the extraction of more information from the data than would be possible otherwise. This comes at a cost of theory-ladenness. We discuss the issue of inferential circularity, which arises in some applications; classify some of the epistemic strategies used to reduce the extent of theory-ladenness; and discuss ways in which these strategies are model independent
Can Generative AI Produce Novel Evidence?
Get PDFResearchers in the historical sciences explore the use of generative AI (GenAI) systems for reconstructing destroyed manuscripts and artifacts. This paper poses a novel question: can such GenAI systems generate evidence that provides new knowledge about the world or can they only produce hypotheses that we might seek evidence for? Exploring responses to this question, the paper argues that 1) GenAI outputs can at least be understood as higher-order evidence (Parker 2022) and 2) may also produce de novo synthetic evidence
Locality in the Heisenberg picture
Get PDFQuantum entanglement is widely regarded as a nonlocal phenomenon, but Deutsch and Hayden (2000) have recently received growing support for their claim that in the Heisenberg picture, entanglement can be characterised locally using objects they call descriptors. I argue that the notion of locality underlying this claim is a flawed version of the principle of separability that I call spatial separability. An improved version, spatiotemporal separability, reveals that their claim is false. The proposed analysis of separability also reveals the crucial feature of quantum theory that makes it 'spooky' in any picture: quantum entanglement entails that there are non-qualitative properties, which are profoundly different from the qualitative properties we have come to expect from classical physics