Evènements

Juin 2017

Vendredi, 23 Juin, 2017

Séminaire

Valerio Lucarini

Department of Mathematics and Statistics, University of Reading, UK
CEN, University of Hamburg, Germany

 

The climate is a complex, chaotic, non-equilibrium system featuring a limited horizon of predictability and variability on a vast range of temporal and spatial scales. We show how the Ruelle response theory allows for predicting climate change –  global averages and spatial patterns - using Green functions constructed for comprehensive global climate models. We show how a breakdown of the Ruelle formulas occurs near climatic critical transitions. We find evidence of a clear violation of the fluctuation-dissipation theorem and clarify its theoretical reasons and practical relevance. Finally, we address the problem of climate multistability resulting from the ice-albedo feedback, and find the Melancholia state, i.e. the edge state between the two attractors corresponding to the co-existing warm and snowball climate states. The Melancholia state is the gate for the noise-inducted transitions between the two stable states.

 

Vendredi, 30 Juin, 2017

Séminaire

Davide Rossini

Università degli Studi di Pisa

Cold atomic gases endowed with a synthetic dimension are emerging as an ideal platform to address the interplay between interactions and static gauge fields. A fundamental question is whether these setups can give access to pristine two-dimensional phenomena, such as the fractional quantum Hall effect, and how. We show that unambiguous signatures of Laughlin-like states can be observed and characterized in synthetic ladders, thus being related to an unconventional fractional quantum Hall effect in the thin-torus limit. In particular we demonstrate the existence of a hierarchy of fractional insulating and conducting states, showing that the gapped states are characterized by density and magnetic order, whereas the gapless phases can support helical modes. Our analysis provides a guideline towards the observability and understanding of strongly correlated states of matter in synthetic ladders.