nLab no-go theorem

Idea

By a no-go theorem one generally means (commonly so in theoretical physics) a theorem which shows that some approach is not possible even though it may appear as if it should be. In practice, since no-go theorems typically depend on assumptions, they often serve to bring out key loopholes in common arguments.

Examples of no-go theorems in theoretical physics include

in foundations of quantum physics:

• Bell's theorem

• Kochen-Specker theorem

• Gleason's theorem

• Pusey-Barrett-Rudolph theorem

in quantum field theory:

• Coleman-Mandula theorem

in supergravity:

• no de Sitter spacetime (?)

• no ekpyrotic cosmology (?)

Related concepts

mathematical statements

• theory

• judgement, assertion

• hypothesis, consequence

• axiom

• assignment

• definition (inductive, coinductive)

• lemma

• proposition/type (propositions as types)

• theorem

• proof/program (proofs as programs)

• example, counterexample

• conjecture, folklore

• exercise

• analogy

• tautology

• paradox

• no-go theorem