675 research outputs found
Fluidization and Active Thinning by Molecular Kinetics in Active Gels
We derive the constitutive equations of an active polar gel from a model for
the dynamics of elastic molecules that link polar elements. Molecular binding
kinetics induces the fluidization of the material, giving rise to Maxwell
viscoelasticity and, provided that detailed balance is broken, to the
generation of active stresses. We give explicit expressions for the transport
coefficients of active gels in terms of molecular properties, including
nonlinear contributions on the departure from equilibrium. In particular, when
activity favors linker unbinding, we predict a decrease of viscosity with
activity - active thinning - of kinetic origin, which could explain some
experimental results on the cell cortex. By bridging the molecular and
hydrodynamic scales, our results could help understand the interplay between
molecular perturbations and the mechanics of cells and tissues.Comment: 6 pages, 2 figure
Topological spin liquids: Robustness under perturbations
We study the robustness of the paradigmatic kagome Resonating Valence Bond
(RVB) spin liquid and its orthogonal version, the quantum dimer model. The
non-orthogonality of singlets in the RVB model and the induced finite length
scale not only makes it difficult to analyze, but can also significantly affect
its physics, such as how much noise resilience it exhibits. Surprisingly, we
find that this is not the case: The amount of perturbations which the RVB spin
liquid can tolerate is not affected by the finite correlation length, making
the dimer model a viable model for studying RVB physics under perturbations.
Remarkably, we find that this is a universal phenomenon protected by
symmetries: First, the dominant correlations in the RVB are spinon
correlations, making the state robust against doping with visons. Second,
reflection symmetry stabilizes the spin liquid against doping with spinons, by
forbidding mixing of the initially dominant correlations with those which lead
to the breakdown of topological order.Comment: v2: accepted versio
A Possibilistic and Probabilistic Approach to Precautionary Saving
This paper proposes two mixed models to study a consumer's optimal saving in
the presence of two types of risk.Comment: Panoeconomicus, 201
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