Dynamical symmetries in ageing phenomena

Systems undergoing physical ageing can be characterised by (i) undergoing slow relaxation (ii) absence of time-translation-invariance and (iii) dynamical scaling. Specific examples are obtained by quenching many-body systems from a high-temperature initial state to below their critical temperature. Here, we shall consider consequences of an assumed extension of dynamical scaling to a larger group of {\em local scale-transformations}. Explicit scaling forms of two-time responses and correlators are obtained. These will be compared with simulational data in simple magnets, as well as in many-body systems without an equilibrium stationary state, such as critical directed percolation or domain-growth in the Kardar-Parisi-Zhang universality class.\\[4pt] [1] M. Henkel, M. Pleimling, {\it Non-equilibrium phase transitions}, Vol. 2, Springer (Heidelberg 2010) \\[0pt] [2] M. Henkel, J.D. Noh, M. Pleimling, Phys. Rev. {\bf E85}, 030102(R) (2012) {\tt [arxiv:1109.5022]} \\[0pt] [3] M. Henkel, {\tt arxiv:1009.4139} \\[0pt] [4] M. Henkel, S. Stoimenov, Nucl. Phys. {\bf B847} [FS], 612 (2011) {\tt [arxiv:1011.6315]}