10 found
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  1.  53
    On automorphism criteria for comparing amounts of mathematical structure.Thomas William Barrett, J. B. Manchak & James Owen Weatherall - 2023 - Synthese 201 (6):1-14.
    Wilhelm (Forthcom Synth 199:6357–6369, 2021) has recently defended a criterion for comparing structure of mathematical objects, which he calls Subgroup. He argues that Subgroup is better than SYM \(^*\), another widely adopted criterion. We argue that this is mistaken; Subgroup is strictly worse than SYM \(^*\). We then formulate a new criterion that improves on both SYM \(^*\) and Subgroup, answering Wilhelm’s criticisms of SYM \(^*\) along the way. We conclude by arguing that no criterion that looks only to the (...)
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  2.  22
    Supertasks.J. B. Manchak & Bryan W. Roberts - 2022 - Stanford Encyclopedia of Philosophy.
    A supertask is a task that consists in infinitely many component steps, but which in some sense is completed in a finite amount of time. Supertasks were studied by the pre-Socratics and continue to be objects of interest to modern philosophers, logicians and physicists. The term “super-task” itself was coined by J.F. Thomson (1954). Here we begin with an overview of the analysis of supertasks and their mechanics. We then discuss the possibility of supertasks from the perspective of general relativity.
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  3.  67
    Malament–Hogarth Machines.J. B. Manchak - 2020 - British Journal for the Philosophy of Science 71 (3):1143-1153.
    This article shows a clear sense in which general relativity allows for a type of ‘machine’ that can bring about a spacetime structure suitable for the implementation of ‘supertasks’. 1Introduction2Preliminaries3Malament–Hogarth Spacetimes4Machines5Malament–Hogarth Machines6Conclusion.
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  4.  61
    Would two dimensions be world enough for spacetime?Samuel C. Fletcher, J. B. Manchak, Mike D. Schneider & James Owen Weatherall - 2018 - Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 63:100-113.
    We consider various curious features of general relativity, and relativistic field theory, in two spacetime dimensions. In particular, we discuss: the vanishing of the Einstein tensor; the failure of an initial-value formulation for vacuum spacetimes; the status of singularity theorems; the non-existence of a Newtonian limit; the status of the cosmological constant; and the character of matter fields, including perfect fluids and electromagnetic fields. We conclude with a discussion of what constrains our understanding of physics in different dimensions.
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  5.  23
    General Relativity as a Collection of Collections of Models.J. B. Manchak - 2021 - In Judit Madarász & Gergely Székely (eds.), Hajnal Andréka and István Németi on Unity of Science: From Computing to Relativity Theory Through Algebraic Logic. Springer. pp. 409-425.
    One usually identifies a particular collection of geometric objects with the models of general relativity. But within this standard collection lurk ‘physically unreasonable’ models of spacetime. If such models are ruled out, attention can be restricted to some sub-collection of ‘physically reasonable’ models which can be considered a variant theory of general relativity. Since we have yet to identify a privileged sub-collection of ‘physically reasonable’ models, it is helpful to think of ‘general relativity’ in a pluralistic way; we can study (...)
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  6.  64
    Paradox Regained? A Brief Comment on Maudlin on Black Hole Information Loss.J. B. Manchak & James Owen Weatherall - 2018 - Foundations of Physics 48 (6):611-627.
    We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin's response to it.
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  7.  30
    Some “No Hole” Spacetime Properties are Unstable.J. B. Manchak - 2018 - Foundations of Physics 48 (11):1539-1545.
    We show a sense in which the spacetime property of effective completeness—a type of “local hole-freeness” or “local inextendibility”—is not stable.
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  8.  38
    A Hierarchy of Spacetime Symmetries: Holes to Heraclitus.J. B. Manchak & Thomas Barrett - forthcoming - British Journal for the Philosophy of Science.
  9.  12
    On the (In?)Stability of Spacetime Inextendibility.J. B. Manchak - forthcoming - Philosophy of Science:1-12.
    Leibnizian metaphysics underpins the universally held view that spacetime must be inextendible – that it must be “as large as it can be” in a sense. But here we demonstrate a surprising fact within the context of general relativity: the property of inextendibility turns out to be unstable when attention is restricted to certain collections of “physically reasonable”spacetimes.
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  10.  43
    A remark on ‘time machines’ in honor of Howard Stein.J. B. Manchak - 2019 - Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 67:111-116.
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