No-go theorem

Not to be confused with No-ghost theorem.

In theoretical physics, a no-go theorem is a theorem that states that a particular situation is not physically possible. Specifically, the term describes results in quantum mechanics like Bell's theorem and the Kochen–Specker theorem that constrain the permissible types of hidden variable theories which try to explain the apparent randomness of quantum mechanics as a deterministic model featuring hidden states.

Examples

The Weinberg–Witten theorem states that massless particles (either composite or elementary) with spin j > 1/2 cannot carry a Lorentz-covariant current, while massless particles with spin j > 1 cannot carry a Lorentz-covariant stress-energy. The theorem is usually interpreted to mean that the graviton (j = 2) cannot be a composite particle in a relativistic quantum field theory.

In quantum information theory, a no-communication theorem is a result that gives conditions under which instantaneous transfer of information between two observers is impossible.

Other examples:

• Coleman–Mandula theorem
• Haag–Lopuszanski–Sohnius theorem
• Antidynamo theorems (e.g. Cowling's theorem)
• No-teleportation theorem
• No-cloning theorem
• No-broadcast theorem
• Quantum no-deleting theorem

See also

• Earnshaw's theorem states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges.
• Gleason's theorem
• Haag's theorem
• Hohenberg–Kohn theorems
• Nielsen–Ninomiya theorem

External links

• Beating no-go theorems by engineering defects in quantum spin models (2014)