Classicalization is a mechanism of UV completion of theories, which is alternative to the standard ones.
In theories with higher dimensinal operators usual field theoretical calculations lead to violation of unitarity at energies above some cut-off scale. Thus, some UV completion is required for such tehories.
The standard known examples of UV completions in the field theories are:
- The Wilsonian (perterbative) UV completion, where the unitarity is restored by additional weakly coupled degrees of freedom with the mass below the strong coupling scale. The well known example is the Higgs mechanism.
- UV completion in asymptotically free theories. Example – QCD, where the theory at low energies is formulated in terms of mesons, while at high energies the description should be switched to quarks and gluons.
In the classicalization it is stated that some specific theories may complete themeselves at high energies by specific dynamics. It is expectd, that in certain theories with derivative coupling in high energy collisions large field configurations (Classicalon
s) are formed, preventing the theory from accessing to small scale (i.e. high energy) dynamics. This scale grows with energy, leading to "classical" geometric cross-sections (as opposed to normal "quantum" behavior, where the scales, relevant for high energies, become smaller).
One of the theories, that is conjectured to excibit the classicalization behavior is gravity, where at high (transplanckian) energies scattering is expected to be saturated by creation of classical large black holes.
At present, no explicit (full) field theoretical calculations, confirming classicalization, exists.