Writings

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L. Craig Evans is a professor at UC Berkeley. For many students he is best known for his textbook on partial differential equations. I …
Last updated on 10 min read notes from talks

Let's start with something simple: Given a circle with radius $R$, draw a concentric circle with radius 1 larger. How much longer is …
Last updated on 3 min read mathematical diversions

When does a polynomial with real coefficients have only real roots? Here's one way to determine it.
Last updated on 4 min read expository

Driving down the highway in upstate Michigan yesterday, I saw a State Police billboard that states (I paraphrase) Drivers who text are …
Last updated on 7 min read expository

Here's a slightly non-obvious relation between some angles, that I ran into accidentally. Claim: (angles below given in degrees) \[ …
Last updated on 1 min read mathematical diversions

A short note about an implicit assumption behind the notion of expectation values, and how it relates to economics applications.
Last updated on 7 min read mathematical diversions

I try to reformulate an idea of Capoferri and Vassiliev in the infinitesimal limit and see where it goes.
Last updated on 5 min read research

A follow up to my previous post on Young's inequality.
Last updated on 10 min read expository

Some introductory notes about the definition and geometry of Lie groups, and their analysis.
Last updated on 19 min read expository

As we all learned in a first course in PDEs, for "reasonable" initial data $u_0$, the solution to the linear heat equation …
Last updated on 4 min read mathematical diversions