- On the dimensionality of spacetime (space.mit.edu)
Some superstring theories have more than one effective low-energy limit corresponding to classical spacetimes with different dimensionalities. We argue that all but the (3 + 1)-dimensional one might correspond to ‘dead worlds’, devoid of observers, in which case all such ensemble theories would actually predict that we should find ourselves inhabiting a (3 + 1)-dimensional spacetime. With more or less than one time dimension, the partial differential equations of nature would lack the hyperbolicity property that enables observers to make predictions. In a space with more than three dimensions, there can be no traditional atoms and perhaps no stable structures. A space with less than three dimensions allows no gravitational force and may be too simple and barren to contain observers.
- Cohen the Barbarian (Wikipedia)
Ghenghiz Cohen, known as Cohen the Barbarian, is a hero in the classical sense, i.e., a professional thief, brawler and ravisher of women. Cohen is introduced in the second Discworld novel, The Light Fantastic, with significant returns in Interesting Times and then with his last appearance in The Last Hero. His name and character are an obvious echo of Robert E. Howard’s Conan the Barbarian and Genghis Khan, and of the common Jewish surname Cohen.