# Graviscalar

(Redirected from Radion (physics))

In theoretical physics, a graviscalar (also known as a radion) is a hypothetical particle that emerges as an excitation of the metric tensor (i.e. gravitational field) but whose physical properties are virtually indistinguishable from a scalar in four dimensions, as shown in Kaluza–Klein theory. The scalar field ${\displaystyle \phi }$ comes from a component of the metric tensor ${\displaystyle g_{55}}$ where the figure 5 labels an additional, fifth dimension. It can be thought of as a measure of the size of the extra dimension, with variations in the scalar field representing variations in the size of the extra dimensions.

In models with multiple extra dimensions, there exist several such particles.

In theories with extended supersymmetry, a graviscalar is usually a superpartner of the graviton that behaves as a particle with spin 0.

This concept is closely related to that of gauged Higgs models.