Aging under Shear: Structural Relaxation of a Non-Newtonian Fluid

The influence of an applied shear field on the dynamics of an aging colloidal suspension has been investigated by the dynamic light scattering determination of the density autocorrelation function. Though a stationary state is never observed, the slow dynamics crosses between two different non-equilibrium regimes as soon as the structural relaxation time approaches the inverse shear rate. In the shear dominated regime (at high shear rate values) the structural relaxation time is found to be strongly sensitive to shear rate while aging proceeds at a very slow rate. The effect of shear on the detailed shape of the density autocorrelation function is quantitatively described assuming that the structural relaxation process arises from the heterogeneous superposition of many relaxing units each one independently coupled to shear with a parallel composition rule for timescales.Comment: 5 pages, 5 figure

L∞-norm and energy quantization for the planar Lane–Emden problem with large exponent

For any smooth bounded domain (Formula presented.), we consider positive solutions to (Formula presented.)which satisfy the uniform energy bound (Formula presented.)for (Formula presented.). We prove convergence to (Formula presented.) as (Formula presented.) of the (Formula presented.)-norm of any solution. We further deduce quantization of the energy to multiples of (Formula presented.), thus completing the analysis performed in De Marchis et al. (J Fixed Point Theory Appl 19:889–916, 2017)

Colloidal attraction induced by a temperature gradient

Colloidal crystals are of extreme importance for applied research, such as photonic crystals technology, and for fundamental studies in statistical mechanics. Long range attractive interactions, such as capillary forces, can drive the spontaneous assembly of such mesoscopic ordered structures. However long range attractive forces are very rare in the colloidal realm. Here we report a novel strong and long ranged attraction induced by a thermal gradient in the presence of a wall. Switching on and off the thermal gradient we can rapidly and reversibly form stable hexagonal 2D crystals. We show that the observed attraction is hydrodynamic in nature and arises from thermal induced slip flow on particle surfaces. We used optical tweezers to directly measure the force law and compare it to an analytic prediction based on Stokes flow driven by Marangoni forces.Comment: 4 pages, 4 figure

Geo-neutrinos

We review a new interdisciplinary field between Geology and Physics: the study of the Earth's geo-neutrino flux. We describe competing models for the composition of the Earth, present geological insights into the make up of the continental and oceanic crust, those parts of the Earth that concentrate Th and U, the heat producing elements, and provide details of the regional settings in the continents and oceans where operating and planned detectors are sited. Details are presented for the only two operating detectors that are capable of measuring the Earth's geo-neutrinos flux: Borexino and KamLAND; results achieved to date are presented, along with their impacts on geophysical and geochemical models of the Earth. Finally, future planned experiments are highlighted

Quasi-radial solutions for the Lane–Emden problem in the ball

We consider the Lane-Emden problem in the unit ball B of ℝ^2 centered at the origin with Dirichlet boundary conditions and exponent ∈(1,+∞) of the power nonlinearity. We prove the existence of sign-changing solutions having 2 nodal domains, whose nodal line does not touch ∂ and which are non-radial. We call these solutions quasi-radial. The result is obtained for any p sufficiently large, considering least energy nodal solutions in spaces of functions invariant under suitable dihedral groups of symmetry and proving that they fulfill the required qualitative properties. We also show that these symmetric least energy solutions are instead radial for p close enough to 1, thus displaying a breaking of symmetry phenomenon in dependence on the exponent p. We then investigate the nonradial bifurcation at certain values of p from the sign-changing radial least energy solution of.. The bifurcation result gives again, with a different approach and for values of p close to the ones at which the bifurcations appear, the existence of non-radial but quasi-radial nodal solutions

The likelihood for supernova neutrino analyses

We derive the event-by-event likelihood that allows to extract the complete information contained in the energy, time and direction of supernova neutrinos, and specify it in the case of SN1987A data. We resolve discrepancies in the previous literature, numerically relevant already in the concrete case of SN1987A data.Comment: 7 pages, 2 figures. Accepted for publication in PR