Centre de Physique Théorique


Mercredi 15 novembre 2017

XIIIe Ecole de Cosmologie

XIIIe Ecole de Cosmologie

Ecole thématique du CNRS organisée par François Bouchet (IAP) et Roland Triay (CPT)

This school, which is open to international students, has as objectives the reciprocal upgrade and the development of a multidisciplinary community on the research lines promoted by the CNRS. It will favour the transfer of methods/techniques and the development of a multidisciplinary community that is either connected or interested in the massive data processing and statistical analysis. It will train new generations of researchers, notably on the basis of the existing Planck community. They will thus be able to take up the many challenges of all kinds that these ambitious projects involve, on theoretical aspects, instrumental ones and analysis of massive and complex data. The competencies (already obtained) in the processing of data are of interest to other scientific communities which have already expressed their interest, which will lead to the creation of networks for exchanges and collaborations.

13h00 – 15h00, Amphi 5 - CPT

Étude de problèmes inverses et directs pour différentes équations aux dérivées partielles

Yavar KIAN

Soutenance HDR Yavar Kian

15h30 – 17h00, Amphi 5 du CPT

Emergence : from spins to charges

Peter Holdsworth (ENS Lyon)

Emergence is one of the major buzz words of our times - but what does it mean ? Many things to many people is the answer. My working definition, which gives plenty of room for manoeuvre is : the appearance of unexpected many body phenomena, given the symmetries of the Hamiltonian and degrees of freedom at the microscopic level. In this colloquium I will discuss two topical examples in which the quasi-particle excitations of a model spin system with discrete symmetry appear as the topological charges of an emergent electro-magnetic field. In the planar clock model in two dimensions one finds the now famous Kosterlitz-Thouless phase transition which is a confinement - deconfinement transition of emergent electric charge. In the frustrated magnetic material, spin ice the quasi-particles appear to be freely moving magnetic charge - magnetic monopoles - and the system emerges as a magnetic Coulomb fluid in the grand canonical ensemble. With the addition of quantum fluctuations the emergent magneto-statics develops further into a complete analogue of quantum electrodynamics. I will aliment this discussion with experimental results from a wide range of systems.