Archive for the ‘Physics’ Category

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DAY-O-WIPs 3.0

June 16, 2014

“Scales of Motion, Atmospheric Dynamics and Clouds” Marina Baldissera Pacchetti

“William Henry Bragg and the Nature of X-Rays” Haixin Dang

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The Problem of Space

May 28, 2014

Joshua Eisenthal

Abstract: I define the Problem of Space as the problem of delimiting the range of candidate geometrical descriptions of physical space. I argue that, ever since the development of non-Euclidean geometries, tackling the Problem of Space has become necessary in order to understand thespatial significance of geometrical structures.

I briefly review the nineteenth century approach to this problem, arriving at the so-called “classical solution”. This solution centered around the claim, advanced by Helmholtz and Poincaré, that candidate physical geometries were just those structures which could represent the free mobility of rigid bodies. As noted originally by Riemann, then argued for by Helmholtz and proved rigorously by Lie, congruence relations which could represent such free mobility existed only in geometries of constant curvature. Helmholtz and Poincaré regarded this fact as providing the means of delimiting the range of spatially significant geometrical structures.

However, I then review how this view was fatally undermined by the development of general relativity. I thus turn to explore the twentieth century solution to the Problem of Space advanced by Hermann Weyl. I conclude by reflecting on the significance of this discussion for a relatively recent dispute regarding the status of the metric field in general relativity. I suggest that this dispute has arisen partially due to a failure to properly appreciate the insights made available by the kind of sophisticated analysis of geometrical concepts exemplified by Weyl’s work. More generally, I argue that the nuances of Weyl’s view demonstrate the importance of engaging with the Problem of Space in interpreting general relativity today.

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Equivalence Principle Tests

April 3, 2014

Nora Mills Boyd

Abstract: The Equivalence Principle supposedly plays a central role in characterizing the theory of general relativity and in particular, the geometric interpretation of gravity.  Moreover, null results from decades of experimental research looking for violations of the EP contribute support to the claim that GR has passed all experimental tests so far.  However, there is significant disconnect between formulations of the principle in theoretical physics and philosophical literatures on one hand, and experimental practice on the other.  Precise formulations of the principle typically apply strictly to abstract or highly idealized systems involving force-free ‘test’ bodies, perfectly homogeneous gravitational fields, and infinitesimally small regions. In striking contrast, EP experimentalists measure and manage forces, account for tidal effects, and capitalize on (or compensate for) the inhomogeneous gravitational environments of real, physically extended, laboratories.  So what do null results from experiments searching for EP violations actually tell us about GR?  The present project aims to bridge the gap between the conceptual foundations of GR and the experiments that supposedly support that theory.  To do this, I emphasize the importance of measuring and engineering particular gravitational environments in EP experiments.

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Axiomatic Quantum Field Theory in the Philosophy of Quantum Field Theory

March 14, 2014

Bihui Li

Abstract: The philosophy of quantum field theory (QFT) in North America is dominated by philosophers working in the algebraic QFT tradition. They justify their choice of this tradition by a methodological requirement that when philosophers of physics study a theory T, the referent of T must be some mathematically well-defined structure. At the same time, philosophers think that their preferred axiomatic versions of QFT are best suited for “foundational”, “fundamental”, or “ontological” inquiries. I argue that the mathematical structures satisfying the methodological requirement are not always the best starting points for foundational, fundamental, or ontological inquiries. Many foundational, fundamental, and ontological questions are best addressed by constructive QFT, which starts with the ill-defined formalisms of Lagrangian QFT and tries to make them well-defined.  Because different interactions in constructive QFT require different mathematical constructions, the mathematical structures required cannot be determined prior to constructing a solution for a particular interaction. In contrast, the advantage of axiomatic QFT is its independence from the specific interactions being modeled, but this independence also means that it cannot provide many kinds of foundational, fundamental, or ontological information.

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Quantum Mechanics in Time and Space

January 27, 2014

Thomas Pashby

Abstract: There is a common understanding of quantum mechanics as a theory of instantaneous measurements of possible properties of systems.  I show that this view cannot account for typical experimental results concerning the time and location of detection events.  The alternative view I provide resists the idea that experimental physics consists of experiments performed at freely chosen moments of time.  This offers a potential resolution of conceptual difficulties surrounding measurement as characterized by Schroedinger’s famous cat paradox. Instead, I supply the means for a re-conceptualization of quantum mechanics as a theory of spatio-temporally located events.

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Day-O-WIPs Beta

June 17, 2013

The second installment of the “Day-O-WIPs” series:

“Toward a Philosophy of Synthetic Science” Julia Bursten

“Can Genes be Darwinian Individuals?” Haixin Dang

“Group Theory or No Group Theory: Understanding Atomic Spectra” Joshua Hunt

“Dynamical Models: A Type of Mathematical Explanation in Neuroscience and Medicine” Lauren Ross

“The Wax & the Mechanical Mind: Reexamining Hobbes’s Objections to Descartes’ Meditations” Marcus Adams

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Day-O-WIPs 1.0

June 11, 2013

An unprecedented workshop-style afternoon packed with  five different WIPs:

“It is a good thing for every man to know a little about astronomy; it will make him a better man” Nora Boyd

“Boundary Conditions, Laws, and Nomological Content in Quantum Scattering Theory” Bihui Li

“From Waveguides to Field Theory” Michael Miller

“Psychiatric Objects in Research and Practice: Introducing the RDoC”  Kathryn Tabb

“Range Content, Attention, and the Precision of Representation” Trey Boone