Science and the Founding Fathers

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Another post from the History Book Club. It seemed particularly appropriate for today (January 20th, Inauguration Day).

Science and the Founding Fathers: Science in the Political Thought of Thomas Jefferson, Benjamin Franklin, John Adams, and James Madison,
by I. Bernard Cohen, W.W. Norton & Company, 1995.

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Cornflakes and Bonti Knives

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Wikimedia Commons

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The −1 Dimensional Reduced Homology Group of the Empty Set

Hatcher’s Algebraic Topology unfortunately hadn’t been written when I studied the subject in grad school, but a few years ago I participated in a meetup that went through about half of it. I wrote up notes on things I puzzled over, or just observations I found helpful. Here they are. Besides the homology group mentioned in the title, some other tidbits: a figure to elucidate the calculation of the fundamental group of the complement of the Alexander Horned Sphere, and more details for the intuitive proof Hatcher sketches of Poincaré duality.

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The Peloponnesian War

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Socrates, Bad Guy

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The Death of Socrates, Jacques Louis David.
(From Wikimedia Commons)

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Gracefully Insane

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Topics in Nonstandard Arithmetic 9: Tricks with Quantifiers

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Every specialty has its tricks of the trade. They become second nature to practitioners, so they often don’t make it into the textbooks. Quantifiers rule in logic; here are some of the games we can play with them. I’ll start with tricks that apply in logic generally, then turn to those specific to Peano arithmetic.

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The Second French Revolution

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Delacroix’s Liberty Leading the People

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Topics in Nonstandard Arithmetic 8: Extensions and Substructures

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Substructures and extensions loom large in math: subgroups, subrings, extension fields, submanifolds, subspaces of topological spaces… So too in the model theory of PA.

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Nonstandard Models of Arithmetic 24

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Next Paris-Harrington post

MW: Indicators: we don’t need to discuss these, to prove the Paris-Harrington theorem. But I think they offer valuable insight.

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