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| de Sitter |
 Title text: Our anti-de Sitter club is small at the moment, but I've started corresponding with the conformal field theory people. |
Explanation
An anti-de Sitter space (AdS) is a space which has constant negative (hyperbolic) spatial curvature, in which the sum of the internal angles of triangles is less than 180° and two parallel lines will diverge when extended. AdS is a theoretical space with strange curves and extra dimensions which is used in studying the space-time structure of the universe. This is in contrast to a de Sitter space, which has constant positive (elliptic) curvature, the sum of a triangle's angles is more than 180°, and lines that initially appear parallel will always meet; a sphere is an example of a de Sitter space. The caption "My house is an anti-de Sitter space" refers instead to being against the actual physicist Willem de Sitter, after whom both spatial geometries are named, because the speaker forbids de Sitter from entering their house.
The title text refers to conformal field theory (CFT), a set of rules for how tiny particles behave on boundaries. The ideas of CFT and AdS are closely linked: everything in an AdS has a parallel in CFT, a property which is usually called the AdS/CFT correspondence.
Transcript
- [A large note is taped to a closed door, which has a doorknob with a keyhole on it. The note reads:]
- 20th century Dutch physicist Willem de Sitter is not welcome here
- [Caption below the panel:]
- My house is an anti-de Sitter space.
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