In physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and in particular in the theory of magnetism

Magnetism

Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...

, an antidynamo theorem is one of several results that restrict the type of magnetic fields that may be produced by dynamo

Dynamo theory

In geophysics, dynamo theory proposes a mechanism by which a celestial body such as the Earth or a star generates a magnetic field. The theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time...

 action.

One notable example is Cowling's antidynamo theorem which states that no axisymmetric magnetic field can be maintained by dynamo action. It is also known that two-dimensional magnetic fields are forbidden.

The impact of the known anti-dynamo theorems is that successful dynamos do not possess a high degree of symmetry.