Freund–Rubin compactification

Freund–Rubin compactification is a method used in the context of string theory and higher-dimensional theories of gravity, particularly in relation to the compactification of extra dimensions. The concept was introduced by Justin Freund and Marvin Rubin in the early 1980s. In string theory and related theories, we often encounter scenarios where the observable universe is modeled as a four-dimensional spacetime (3 spatial dimensions plus time) embedded within a higher-dimensional space.