How does string theory connect extra dimensions to multiverse theories?

In string theory, the connection to multiverse theories is primarily established through the geometry of extra dimensions. While the familiar world consists of four dimensions (three of space and one of time), string theory requires additional spatial dimensions—typically six or more—that are "compacted" or curled up at every point in space-time.123

The configuration of these compact, extra-dimensional spaces is critical because it determines the physical conditions of the universe, including the values of physical constants and the vacuum energy. Because the equations of string theory allow these extra dimensions to take a vast number of different geometric forms, each configuration can result in a different set of physical laws.21

When combined with the concept of eternal inflation, this leads to the "eternal inflation/string landscape" model. In this framework, transitions between different geometric configurations of the extra dimensions can occur, generating a multiverse of regions with varying physical constants and fields. This landscape provides a potential anthropic explanation for why our universe possesses constants—such as the cosmological constant—that are uniquely suited for life.2