dimensionchanging

Dimension changing is a term used in physics and mathematics to describe processes or theories in which the effective number of dimensions of a system changes. In physics, this usually concerns spacetime dimensions, while in mathematics dimension is a formal property of a space that can be discussed in different contexts.

In physics, dimension changing commonly appears in theories with extra spatial dimensions. Early ideas, such as Kaluza-Klein theory, posited additional compactified dimensions beyond the familiar three of space and one of time. In string theory and M-theory, the consistent framework requires more than four spacetime dimensions (often 10 or 11 total), with the extra dimensions hidden at low energies through compactification or brane configurations. Some models describe cosmological evolution where the observed dimensionality could effectively change, for example if extra dimensions either expand, contract, or become inaccessible to standard-model fields. In braneworld scenarios, ordinary matter is confined to a three-plus-one dimensional brane while gravity can explore higher dimensions, altering the apparent dimensionality at different scales.

In mathematics and related disciplines, dimension can be context-dependent. The topological, metric, or fractal dimension of a set may vary with the scale of measurement, as seen in fractals, where complex structure yields a dimension between integers. More generally, passing to subspaces, quotients, or products with other spaces can change the ambient dimension of a construction, though many notions of dimension remain invariant under standard equivalences.

Overall, literal, dynamic changes in the total number of dimensions are speculative and subject to strong theoretical and observational constraints, but the concept serves as a useful framework in discussions of high-energy physics, cosmology, and geometry.