Daily Archives: July 30, 2014

Café Talk

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cafe_sketch_27_06_14 Here’s a quick sketch I did while in Princeton last month, at a new café, Café Vienna. (See earlier posts here and here for sketches in an older Princeton Café. I’m using a thicker marker for this one, by contrast, giving a different feel altogether, more akin to this one.) This new café promises to recreate the atmosphere of the Cafés of Vienna and so I kind of had to have coffee there before I left. Why?

Well, two reasons, one obvious and the other less so: […] Click to continue reading this post →

Triply Dyonic

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dyon_phase_diagramsI thought I’d mentioned this already, but I could not find anything after a search on the blog so somehow I think I must have forgotten to. It is a cute thing about a certain favourite solution (or class of solutions) of Einstein’s equations that I’ve talked about here before. I’m talking about the Taub-NUT solution (and its cousin, Taub-Bolt). Taub-NUT is sort of interesting for lots of reasons. Many, in fact. One of them concerns it having both mass [tex]M[/tex] and another parameter called “nut charge”, [tex]N[/tex]. There are several ways to think about what nut charge is, but one curious way is that is is sort of a “magnetic” counterpart to the ordinary mass, which can be thought of as an “electric” quantity.

The language is based on analogy with electromagnetism, where, in the usual […] Click to continue reading this post →