Fluidity and supercriticality of the QCD matter created in relativistic heavy ion collisions

In this paper we discuss the fluidity of the hot and dense QCD matter created in ultrarelativistic heavy ion collisions in comparison with various other fluids, and in particular suggest its possible supercriticality. After examining the proper way to compare non-relativistic and relativistic fluids from both thermodynamic and hydrodynamic perspectives, we propose a new fluidity measure which shows certain universality for a remarkable diversity of critical fluids. We then demonstrate that a fluid in its supercritical regime has its fluidity considerably enhanced. This may suggest a possible relationship between the seemingly good fluidity of the QCD matter produced in heavy ion collisions at center of mass energy of $\sqrt{s}=200 \rm AGeV$ and the supercriticality of this matter with respect to the Critical-End-Point on the QCD phase diagram. Based on such observation, we predict an even better fluidity of the matter to be created in heavy ion collisions at LHC energy and the loss of good fluidity at certain lower beam energy. Finally based on our criteria, we analyze the suitability of a hydrodynamic description for the fireball evolution in heavy ion collisions at various energies.Comment: 12 pages, 6 figures; minor corrections; final version published in PR

Cooperativity flows and Shear-Bandings: a statistical field theory approach

Cooperativity effects have been proposed to explain the non-local rheology in the dynamics of soft jammed systems. Based on the analysis of the free-energy model proposed by L. Bocquet, A. Colin \& A. Ajdari ({\em Phys. Rev. Lett.} {\bf 103}, 036001 (2009)), we show that cooperativity effects resulting from the non-local nature of the fluidity (inverse viscosity), are intimately related to the emergence of shear-banding configurations. This connection materializes through the onset of inhomogeneous compact solutions (compactons), wherein the fluidity is confined to finite-support subregions of the flow and strictly zero elsewhere. Compactons coexistence with regions of zero fluidity ("non-flowing vacuum") is shown to be stabilized by the presence of mechanical noise, which ultimately shapes up the equilibrium distribution of the fluidity field, the latter acting as an order parameter for the flow-noflow transitions occurring in the material.Comment: 33 pages, 10 figure

Fluidity Onset in Graphene

Viscous electron fluids have emerged recently as a new paradigm of strongly-correlated electron transport in solids. Here we report on a direct observation of the transition to this long-sought-for state of matter in a high-mobility electron system in graphene. Unexpectedly, the electron flow is found to be interaction-dominated but non-hydrodynamic (quasiballistic) in a wide temperature range, showing signatures of viscous flows only at relatively high temperatures. The transition between the two regimes is characterized by a sharp maximum of negative resistance, probed in proximity to the current injector. The resistance decreases as the system goes deeper into the hydrodynamic regime. In a perfect darkness-before-daybreak manner, the interaction-dominated negative response is strongest at the transition to the quasiballistic regime. Our work provides the first demonstration of how the viscous fluid behavior emerges in an interacting electron system.Comment: 8pgs, 4fg

Economic Boom and Social Mobility: The Irish Experience

In this paper we examine the consequences for social mobility patterns of the unprecedented period of economic growth experienced in Ireland over the 1990s and the implications of developments for current theories of social fluidity. Contrary to suggestions that the ?Celtic Tiger? experience has been associated with a deepening problem of marginalization we found evidence for a substantial upgrading of the class structure and increased levels of social mobility. We also found evidence for increased social fluidity in relation to long-range hierarchical mobility. Such increased openness could not be explained by changes in the manner in which education mediates the relationship between origins and destinations. There is no necessary relationship between economic growth and social fluidity. However, the pattern of change over time in the Irish case suggests that both long-term factors associated with the upgrading of the class structure and short-term factors reflected in the unprecedented tightness of the labour market have produced a situation where employers have increasingly applied criteria other than education in a manner that has facilitated increased social fluidity. The Irish case provides further support to the argument for reconsidering the balance that mobility research has struck between social fluidity and absolute mobility and encouraging increased attention to the evolution of firms and jobs. It also provides support for the conclusion, that in circumstances where policies in advanced industrial societies have shown an increasing tendency to diverge, increased social fluidity may come about as a consequence of very different economic and social policies.

Performing Gender: A Study of Gender Fluidity

The subjective quality of identity and the relativistic nature of gender are subjects that continue to bemuse and attract social scientists. In this study I examine gender fluidity – an inconsistent gender identity – within the framework of Western ontology. By analyzing narratives, I note that my informants recognize this gender identity as fluctuating feelings (which I call the feelings of gender) that influence how they perceive and interact with their bodies. Furthermore, I examine other important elements that may have influenced my informants\u27 understanding of their gender identities and bodies: upbringing, previous relationships and interactions, communities, and language

Spatial repartition of local plastic processes in different creep regimes in a granular material

Granular packings under constant shear stress display below the Coulomb limit, a logarithmic creep dynamics. However the addition of small stress modulations induces a linear creep regime characterized by an effective viscous response. Using Diffusing Wave Spectroscopy, we investigate the relation between creep and local plastic events spatial distribution ("hot-spots") contributing to the plastic yield. The study is done in the two regimes, i.e. with and without mechanical activation. The hot-spot dynamics is related to the material effective fluidity. We show that far from the threshold, a local visco-elastic rheology coupled to an ageing of the fluidity parameter, is able to render the essential spatio-temporal features of the observed creep dynamics