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Charlotte Werndl
University of Salzburg
Charlotte Sophie Werndl
London School of Economics
  1. Climate Models, Calibration, and Confirmation.Katie Steele & Charlotte Werndl - 2013 - British Journal for the Philosophy of Science 64 (3):609-635.
    We argue that concerns about double-counting—using the same evidence both to calibrate or tune climate models and also to confirm or verify that the models are adequate—deserve more careful scrutiny in climate modelling circles. It is widely held that double-counting is bad and that separate data must be used for calibration and confirmation. We show that this is far from obviously true, and that climate scientists may be confusing their targets. Our analysis turns on a Bayesian/relative-likelihood approach to incremental confirmation. (...)
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  2.  74
    Explaining Thermodynamic-Like Behavior in Terms of Epsilon-Ergodicity.Roman Frigg & Charlotte Werndl - 2011 - Philosophy of Science 78 (4):628-652.
    Gases reach equilibrium when left to themselves. Why do they behave in this way? The canonical answer to this question, originally proffered by Boltzmann, is that the systems have to be ergodic. This answer has been criticised on different grounds and is now widely regarded as flawed. In this paper we argue that some of the main arguments against Boltzmann's answer, in particular, arguments based on the KAM-theorem and the Markus-Meyer theorem, are beside the point. We then argue that something (...)
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  3. Rethinking Boltzmannian Equilibrium.Charlotte Werndl & Roman Frigg - 2015 - Philosophy of Science 82 (5):1224-1235.
    Boltzmannian statistical mechanics partitions the phase space of a sys- tem into macro-regions, and the largest of these is identified with equilibrium. What justifies this identification? Common answers focus on Boltzmann’s combinatorial argument, the Maxwell-Boltzmann distribution, and maxi- mum entropy considerations. We argue that they fail and present a new answer. We characterise equilibrium as the macrostate in which a system spends most of its time and prove a new theorem establishing that equilib- rium thus defined corresponds to the largest (...)
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  4. Entropy - A Guide for the Perplexed.Roman Frigg & Charlotte Werndl - 2011 - In Claus Beisbart & Stephan Hartmann (eds.), Probabilities in Physics. Oxford University Press. pp. 115-142.
    Entropy is ubiquitous in physics, and it plays important roles in numerous other disciplines ranging from logic and statistics to biology and economics. However, a closer look reveals a complicated picture: entropy is defined differently in different contexts, and even within the same domain different notions of entropy are at work. Some of these are defined in terms of probabilities, others are not. The aim of this chapter is to arrive at an understanding of some of the most important notions (...)
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  5.  62
    When Does a Boltzmannian Equilibrium Exist?Charlotte Werndl & Roman Frigg - 2016 - In Daniel Bedingham, Owen Maroney & Christopher Timpson (eds.), Quantum Foundations of Statistical Mechanics. Oxford University Press.
    The received wisdom in statistical mechanics is that isolated systems, when left to themselves, approach equilibrium. But under what circumstances does an equilibrium state exist and an approach to equilibrium take place? In this paper we address these questions from the vantage point of the long-run fraction of time definition of Boltzmannian equilibrium that we developed in two recent papers. After a short summary of Boltzmannian statistical mechanics and our definition of equilibrium, we state an existence theorem which provides general (...)
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  6. Model-Selection Theory: The Need for a More Nuanced Picture of Use-Novelty and Double-Counting.Katie Steele & Charlotte Werndl - 2016 - British Journal for the Philosophy of Science:axw024.
    This article argues that common intuitions regarding (a) the specialness of ‘use-novel’ data for confirmation and (b) that this specialness implies the ‘no-double-counting rule’, which says that data used in ‘constructing’ (calibrating) a model cannot also play a role in confirming the model’s predictions, are too crude. The intuitions in question are pertinent in all the sciences, but we appeal to a climate science case study to illustrate what is at stake. Our strategy is to analyse the intuitive claims in (...)
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  7.  53
    A New Approach to the Approach to Equilibrium.Roman Frigg & Charlotte Werndl - 2012 - In Yemima Ben-Menahem & Meir Hemmo (eds.), Probability in Physics. The Frontiers Collection. Springer. pp. 99-114.
    Consider a gas confined to the left half of a container. Then remove the wall separating the two parts. The gas will start spreading and soon be evenly distributed over the entire available space. The gas has approached equilibrium. Why does the gas behave in this way? The canonical answer to this question, originally proffered by Boltzmann, is that the system has to be ergodic for the approach to equilibrium to take place. This answer has been criticised on different grounds (...)
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  8.  55
    On the History of the Isomorphism Problem of Dynamical Systems with Special Regard to von Neumann's Contribution.Miklos Redei & Charlotte Werndl - 2012 - Archive for History of Exact Sciences 66 (1):71-93.
    This paper reviews some major episodes in the history of the spatial isomorphism problem of dynamical systems theory. In particular, by analysing, both systematically and in historical context, a hitherto unpublished letter written in 1941 by John von Neumann to Stanislaw Ulam, this paper clarifies von Neumann's contribution to discovering the relationship between spatial isomorphism and spectral isomorphism. The main message of the paper is that von Neumann's argument described in his letter to Ulam is the very first proof that (...)
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  9.  60
    Book review: Rationalität in der Angewandten Ethik. [REVIEW]A. J. J. Anglberger, B. Armstrong, W. F. Berger, N. Gratzl & Charlotte Werndl - 2005 - Kriterion - Journal of Philosophy 19 (1):44-53.
    Betrachtet man den Gebrauch der Worte ‘Moral’ und ‘Vernunft’ etwas genauer, so stellt man fest, dass nicht klar ist, was sie bezeichnen bzw. wie Moral und Vernunft zusammenhängen. In dem Buch ‘Rationalität in der Angewandten Ethik’, in dem sich verschiedene Autoren die Aufgabe gestellt haben, diese Umstände in das Licht der Betrachtung zu rücken, finden wir Fragen darüber, wie “Moral”, “Angewandte Ethik” und “Vernunft” (auch in der Anwendung) zu verstehen und zu vereinen sind.
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  10.  41
    Model Tuning in Engineering: Uncovering the Logic.Katie Steele & Charlotte Werndl - 2015 - Journal of Strain Analysis for Engineering Design 51 (1):63-71.
    In engineering, as in other scientific fields, researchers seek to confirm their models with real-world data. It is common practice to assess models in terms of the distance between the model outputs and the corresponding experimental observations. An important question that arises is whether the model should then be ‘tuned’, in the sense of estimating the values of free parameters to get a better fit with the data, and furthermore whether the tuned model can be confirmed with the same data (...)
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