superPlanckian

Super-Planckian describes quantities that exceed the Planck scale, such as energies, field values, or energy densities. The Planck scale is defined by fundamental constants; Planck energy is about 1.22 × 10^19 GeV, Planck length is about 1.616 × 10^-35 meters, and the reduced Planck mass is about 2.4 × 10^18 GeV. At or above these scales quantum gravity effects are expected to become important, and conventional effective field theories may lose reliability.

In cosmology, super-Planckian often refers to large-field inflation, where the inflaton field travels a distance greater than the Planck mass during inflation. Such super-Planckian excursions have implications for the sensitivity of models to ultraviolet physics and to higher-dimensional operators suppressed by the Planck scale, influencing predictions for primordial gravitational waves and non-Gaussianities.

Outside cosmology, the term can denote energy densities or field values beyond Planckian limits, a regime where a UV-complete theory of quantum gravity is expected to be required. In string theory and related approaches, proposals such as the swampland conjectures place constraints on super-Planckian field excursions and the viability of corresponding effective field theories.

The term is descriptive rather than a hard boundary; it signals regimes where quantum gravity or ultraviolet physics cannot be ignored. See also Planck scale, inflation, swampland conjectures.