I am reading Ludwig's paper "Electromagnetic and gravitational responses and anomalies in topological insulators and superconductors", and in this paper, although I am clear how they get the descent equation which introduced the relationship between anomaly and the existence of topological insultor, I am confused about the theta-term they mentioned on section VA5, they said that the integral of anomaly polynomial $\Omega_{2n+2}$ corresponds to the $\theta$ term. Could anyone help and explain to me what is this theta-term referring to and where can I find information about it?


Question: Advice on an inexpensive but very hardy/tough point-and-shoot camera
Answer: Check out the Go Pro cameras. They're marketed as wearable/mountable (e.g. on a surfboard, helmet, car, boat), waterproof sports cameras.

A friend just got one for a trip to Antartica (I can let you know in about 3 weeks when he gets back if it survived ;). He's used it successfully in the surf and on a kayak and is generally pretty happy with it.

They are technically limited in that they have a fixed focal length (170º FOV fisheye) fixed aperture (f/2.8) and fixed focus (0.6m to infinity). Sensor is 5 MP and it takes SD cards.

So if you want a more technically capable camera to get longer zooms and give you larger prints, then check out the usual brand-name water/shock resistant point &amp; shoots.