Berlin 2012 – wissenschaftliches Programm

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 2: "Condensed Metaphysics" II: Specific Models

AGPhil 2.1: Hauptvortrag

Montag, 26. März 2012, 14:30–15:15, E 020

Ising Models: Interpretational and Computational Issues — •Paul Humphreys — Department of Philosophy, University of Virginia, Charlottesville, USA

The class of models that includes Ising models, Potts models, spin glass models and related mathematical objects have been used to model many different condensed matter phenomena. Taking the canonical example of ferromagnetic phase transitions, I shall explore the sense in which Ising models represent real ferromagnets and how and why such a simple model can be successful. Central to this exploration will be the finite dimensional/infinite dimensional comparison and the extent to which relaxing the idealizations of the model (`de-idealizing* it) makes the model more or less accurate. I shall also suggest ways in which Istrail's 2000 proof that computing the partition functions (and hence the exact energy levels) for finite sublattices of non-planar 3D and 2D Ising models are NP-complete problems and Mu et al.'s 2008 result that there are macroscopic properties the values of which cannot be effectively predicted solely on the basis of knowledge of microstates of the system affect what can be known about these models.