0 Memory in the aging of a polymer glass L . Bellon , S . Ciliberto and C .

Low frequency dielectric measurements on plexiglass (PMMA) show that cooling and heating the sample at constant rate give an hysteretic dependence on temperature of the dielectric constant ǫ. A temporary stop of cooling produces a downward relaxation of ǫ. Two main features are observed i) when cooling is resumed ǫ goes back to the values obtained without the cooling stop (i.e. the low temperature state is independent of the cooling history) ii) upon reheating ǫ keeps the memory of the aging history (Memory). The analogies and differences with similar experiments done in spin glasses are discussed.