We proved that all the usual things are equivalent to the axiom of choice: Zorn’s lemma, the well ordering principle, cardinal comparability (given two sets, one must inject into the other), and the ...

every family of well ordered sets has a least member — informally, “the well ordered sets are well ordered”; ...

Earlier this month the Mathematics Institute at Uppsala University hosted a conference called Categorification in Algebra and Topology, clearly a theme close to our collective heart. As yet there are ...

Aug 2, 2008 In this new version of our paper, we systematically explain how n-dimensional field theories give n-plectic manifolds. We also say how a B field affects the 2-plectic structure for a ...

Apr 19, 2017 Conditional entropy, joint entropy and mutual information all have something important to say about the biological diversity of a metacommunity. Pre- and Postdictions of the NCG Standard ...

May 31, 2011 The relationships between Euler characteristic and different kinds of Möbius inversion. This Week’s Finds in Mathematical Physics (Week 295) Apr 17, 2010 In “week295” of This Week’s Finds ...

Sep 18, 2018 Tai-Danae Bradley has a new booklet on applied category theory.

Nov 11, 2024 20:33 Going back and rereading Tom’s old post, what Tom wrote about there amounted to working with a finite parameter set ...

Oct 9, 2007 On weak Lie n-algebras, differential graded Clifford algebra and Roytenberg’s work on weak Lie 2-algebras.

Nov 7, 2024 00:45 Here’s a way to argue that Gerard’s solution to my puzzle is correct. Thurston showed that any star of the ...

Gerard Westendorp has a real knack for geometry, and here is his answer. Here is Thurston’s procedure. First draw the lattice of Eisenstein integers in the complex plane: ...