**math.RA  Rings and Algebras**

- Google's Pagerank algorithm is based, in part, on the singular value decomposition.
- Fourier analysis / transforms and linear algebra is at work in the world millions of times per second (video, audio). In particular, [creating or displaying a JPEG image](http://www.cse.iitk.ac.in/~manindra/CS681/2005/Lecture7.pdf) requires the discrete fourier transform.