Monopoly (physics)
A monopoly ( the monopoly, stress on the first syllable ; ancient Greek from μόνος (monos) = "alone" and Greek πόλος pólos "axis", "axis point") as a physical term is a single pole , for example an electrical point charge .
Use of the term
The first order in the multipole expansion of a field describes a monopole field z. B. the electric field of the total charge reduced to a point of an electric charge distribution . The monopole field is distinguished from the higher orders by its isotropy .
A magnetic monopole is a hypothetical elementary particle or a quasiparticle in certain solids that behaves like a single magnetic pole.
In Yang-Mills theories ( gauge theories with gauge groups that have non-commutative elements), some stable solutions of the field equations characterized by topological invariants are also referred to as (magnetic) monopoles. The electromagnetism is only one special case of a theory ( unitary group ); in other theories, monopoles can exist for both equivalents of electric and magnetic fields .
Sometimes an antenna design in which only half of a dipole antenna (mostly standing vertically) protrudes from the earth is called a "monopole". However, the term “half dipole”, which is also used, is more appropriate here, as it has the same directional characteristic . A non- directional antenna is the hypothetical spherical radiator .
literature
- Horst Stöcker: Pocket book of physics. 4th edition, Verlag Harry Deutsch, Frankfurt am Main, 2000, ISBN 3-8171-1628-4
