6,474 research outputs found
Relationalism about mechanics based on a minimalist ontology of matter
This paper elaborates on relationalism about space and time as motivated by a minimalist ontology of the physical world: there are only matter points that are individuated by the distance relations among them, with these relations changing. We assess two strategies to combine this ontology with physics, using classical mechanics as example: the Humean strategy adopts the standard, non-relationalist physical theories as they stand and interprets their formal apparatus as the means of bookkeeping of the change of the distance relations instead of committing us to additional elements of the ontology. The alternative theory strategy seeks to combine the relationalist ontology with a relationalist physical theory that reproduces the predictions of the standard theory in the domain where these are empirically tested. We show that, as things stand, this strategy cannot be accomplished without compromising a minimalist relationalist ontology
Can Bohmian Mechanics Be Made Background Independent?
The paper presents an inquiry into the question regarding the compatibility
of Bohmian mechanics, intended as a non-local theory of moving point-like
particles, with background independence. This issue is worth being investigated
because, if the Bohmian framework has to be of some help in developing new
physics, it has to be compatible with the most well-established traits of
modern physics, background independence being one of such traits. The paper
highlights the fact that the notion of background independence in the context
of spacetime physics is slippery and interpretation-laden. It is then suggested
that the best-matching framework developed by Julian Barbour might provide a
robust enough meaning of background independence. The structure of Bohmian
dynamics is evaluated against this framework, reaching some intermediate
results that speak in favor of the fact that Bohmian mechanics can be made
background independent.Comment: 24 pages, forthcoming in Studies in History and Philosophy of Modern
Physic
Collapse Theories as Beable Theories
I discuss the interpretation of spontaneous collapse theories, with particular reference to Bell's suggestion that the stochastic jumps in the evolution of the wave function should be considered as local beables of the theory. I develop this analogy in some detail for the case of non-relativistic GRW-type theories, using a generalisation of Bell's notion of beables to POV measures. In the context of CSL-type theories, this strategy appears to fail, and I discuss instead Ghirardi and co-workers' mass-density interpretation and its relation to Schroedinger's original charge-density interpretation. This discussion is extended to relativistic CSL-type theories. A few remarks on Everett's interpretation conclude the paper
Quantum Mechanics on Spacetime I: Spacetime State Realism
What ontology does realism about the quantum state suggest? The main extant
view in contemporary philosophy of physics is wave-function realism. We
elaborate the sense in which wave-function realism does provide an ontological
picture; and defend it from certain objections that have been raised against
it. However, there are good reasons to be dissatisfied with wave-function
realism, as we go on to elaborate. This motivates the development of an
opposing picture: what we call spacetime state realism; a view which takes the
states associated to spacetime regions as fundamental. This approach enjoys a
number of beneficial features, although, unlike wave-function realism, it
involves non-separability at the level of fundamental ontology. We investigate
the pros and cons of this non-separability, arguing that it is a quite
acceptable feature; even one which proves fruitful in the context of
relativistic covariance. A companion paper discusses the prospects for
combining a spacetime-based ontology with separability, along lines suggested
by Deutsch and HaydenComment: LaTeX; 29 pages, 1 Fig. Forthcoming in the British Journal for the
Philosophy of Scienc
Is Quantum Field Theory ontologically interpretable? On localization, particles and fields in relativistic Quantum Theory
In this paper, I provide a formal set of assumptions and give a natural
criterion for a quantum field theory to admit particles. I construct a na\"ive
approach to localization for a free bosonic quantum field theory and show how
this localization scheme, as a consequence of the Reeh-Schlieder theorem, fails
to satisfy this criterion. I then examine the Newton-Wigner concept of
localization and show that it fails to obey strong microcausality and thus is
subject to a more general version of the Reeh-Schlieder theorem. I review
approaches to quantum field theoretic explanations of particle detection events
and explain how particles can be regarded as emergent phenomena of a
relativistic field theory. In particular, I show that effective localization of
Hilbert space vectors is equivalent to an approximate locality of observable
algebras.Comment: 33 page
The Conway-Kochen argument and relativistic GRW models
In a recent paper, Conway and Kochen proposed what is now known as the "Free
Will theorem" which, among other things, should prove the impossibility of
combining GRW models with special relativity, i.e., of formulating
relativistically invariant models of spontaneous wavefunction collapse. Since
their argument basically amounts to a non-locality proof for any theory aiming
at reproducing quantum correlations, and since it was clear since very a long
time that any relativistic collapse model must be non-local in some way, we
discuss why the theorem of Conway and Kochen does not affect the program of
formulating relativistic GRW models.Comment: 16 pages, RevTe
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