Local scale-invariances in the bosonic contact and pair-contact processes

Florian Baumann, Stoimen Stoimenov, Malte Henkel

Published 2005-10-28, updated 2006-03-02Version 2

Local scale-invariance for ageing systems without detailed balance is tested through studying the dynamical symmetries of the critical bosonic contact process and the critical bosonic pair-contact process.Their field-theoretical actions can be split into a Schr\"odinger-invariant term and a pure noise term. It is shown that the two-time response and correlation functions are reducible to certain multipoint response functions which depend only on the Schr\"odinger-invariant part of the action. For the bosonic contact process, the representation of the Schr\"odinger group can be derived from the free diffusion equation, whereas for the bosonic pair-contact process, a new representation of the Schr\"odinger group related to a non-linear Schr\"odinger equation with dimensionful couplings is constructed. The resulting predictions of local scale-invariance for the two-time responses and correlators are completely consistent with the exactly-known results in both models.