This is a collection some of the expository notes that I have written, they range in topic, some closer to my research and some farther away. As opposed to posts in "Mathematical Diversions", posts here are intended to be read by other people. I welcome comments and corrections.

Some notes on the relationship between different models of hyperbolic plane

Preliminaries Here's something I learned from Chongchun Zeng of Georgia Tech, while chatting over some hors-d'oeuvres at the AMS …

A proof of a generalized form of Young's inequality is given without the need of interpolation theory.

A quick introduction of Newton-Cartan theory, which is a sort of Newtonian limit of general relativity from a geometric point of view.

A brief introduction to affine differential geometry and the notion of preferred volume forms.

About the Einstein-Infeld-Hoffmann theorem characterizing geodesics.

The Kempner series recently regained some notoriety due to a Saturday Morning Breakfast Cereal comic (the last panel). The observation …

Expository article on the geometric notion of derivatives.

A converse to Banach's fixed point theorem, due to Bessaga, is discussed.

We explain how to conformally compactify pseudo-Euclidean spaces with $(p,q)$ signature.