Soft Report - Dipartimento di Fisica - Sapienza

Scientific MissionThe scientific works of Soft can be roughly classified in three main Activities that –in the CNR funding scheme- coincide with the three “commesse” in which theresearch center is partitioned. These activities are:A. Non equilibrium dynamics and ComplexityB. Self Assembly, Clustering, Structural ArrestC. Elastic and inelastic X-ray and neutron scatteringThe specific scientific mission of each activity is outlined below.A. Non equilibrium dynamics and ComplexityOne of the characteristic of the CRS SOFT is the long standing expertise of many ofthe senior investigator in the field of undercooled liquids and the glass transition.Taking advantage of this expertise, we are transferring the culture, the tools andthe language pertaining to this fields in the Soft Matter physics. In the undercooledliquids field there are, however, specific sectors that are currently under very quickdevelopment. We think that the deeper investigation of these aspects of the physicsof supercooled liquids, is of fundamental importance for the transfer of knowledgetowards (and backwards) the Soft Matter research. The aim of this activity is tofollow the state of the art research in those sub-fields of the physics of liquids thatare more close to the Soft Matter physics. For this reason we are studying materialswhich are not usually classified as Soft Matter. The specific actions, describedbelow, refer to the study of the interplay between different time-scales in thesystem dynamics. These different time-scales can be either induced by externalflows -as in Research Project A1- or generated by the aging phenomena -as in A2-.The systems that we are investigating include molecular liquids, polymers andcolloids.A1. Slow dynamics of systems in steady states induced by external flows.The aim of this Proget is the study of the dynamics of liquids, polymers and colloidskept off-equilibrium (more specifically: in a steady state) by external forces. Inparticular our goal is the test of the theoretical predictions based on the extensionof the Mode Coupling Theory (MCT) on the shape of the correlation functions [1],and the test of the validity of a generalized form of the dissipation-fluctuation (FD)relation for systems in stationary states [2]. It is also our aim to verify thegenerality of these predictions by investigate a) different kind of systems (rangingfrom molecular glass formers to colloids), b) different kind of observables, and c)different kind of flows. As example of external flows, one can easy think to studysystem under shear (with different time dependence of the shear rate, eitherperiodic or stationary) or system subjected to temperature gradient. Other lesscommon external forces can be also envisaged as, for example, the case of systemsunder composition gradient, or subject to intense electric field as those produced bypulsed Lasers. After the system under investigation has been put in a stationary9SOFT Scientific Report 2004-06