If we use the Friedmann-Lemaitre-Robertson-Walker model for avacuum dominated universe, we see that time may be a function ofa length, the so called co-moving distance. In the FLRW model, thisfunction is injective, so for each time t there is one co moving distancea(t). Straightforwardly, we can assume that time has the dimensionof a length, even if, in a fourdimensional universe, the four dimensionsare not isotropic. Taking account of this hypothesis, we can solve theEPR paradox for entangled states. Moreover, a simple model of antimatter can also be made: antimatter deforms the universe inwardswhile matter deforms the universe outwards. Dark matter is alsodeduced to be a track of massive moving objects within the local curvature of the universe. And finally, taking account that our universeis fourdimensional and that time may be the fourth dimension andhas the dimension of a length, the mystery of dark energy is solved.Indeed, in a fourdimensional universe, what we call dark energy hasa positive pressure which comes naturally from the expansion of theuniverse.

Organic aerogels based on polyurethane were elaborated via sol-gel synthesis and dried with supercritical carbon dioxide (CO2). The influence of the catalyst concentration was investigated, first in order to decrease the reaction kinetics, then to study its impact on the obtained materials properties. It was shown that this parameter also influences the global shrinkage and the bulk density of the resulting materials. Its effect on the dry materials was studied in terms of morphological, textural and thermal properties in order to determine the main correlations thanks to scanning electron microscopy (SEM), nitrogen adsorption, non-intrusive mercury porosimetry and thermal conductivity measurements. Results allowed us to demonstrate a correlation between the bulk density, the texture and the thermal conductivity of this family of polyurethane aerogels and to determine an optimal density range for thermal performance associated with a fine internal mesoporous texture.

A meta-surface made of a collection of nano-resonators characterized an electric dipole and a magnetic dipole was studied in the regime where the wavelength is large with respect to the size of the resonators. An effective description in terms of an impedance operator was derived.

We report on spatially- and time-resolved emission measurements and observation of transport of indirect excitons in ZnO/MgZnO wide single quantum wells.

We study discrete time Markov processes with periodic or open boundaryconditions and with inhomogeneous rates in the bulk. The Markov matrices aregiven by the inhomogeneous transfer matrices introduced previously to prove theintegrability of quantum spin chains. We show that these processes have asimple graphical interpretation and correspond to a sequential update. Wecompute their stationary state using a matrix ansatz and express theirnormalization factors as Schur polynomials. A connection between Bethe rootsand Lee-Yang zeros is also pointed out.

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It is often necessary to tailor nanoparticle (NP) interactions and their compatibility with a polymer matrix by grafting organic groups, but the commonly used silanization route offers little versatility, particularly in water. Herein, alumina-coated silica NPs in aqueous sols have been modified for the first time with low molecular-weight phosphonic acids (PAs) bearing organic groups of various hydrophobicities and charges: propyl, pentyl and octyl PAs, and two PAs bearing hydrophilic groups, either a neutraldiethylene glycol (DEPA) or a potentially charged carboxylic acid (CAPA) group. The interactions and aggregation in the sols have been investigated using zeta potential measurements, dynamic light scattering, transmission electron microscopy, and small-angle scattering methods. The surface modification has been studied using FTIR and 31P MAS NMR spectroscopies. Both high grafting density r and high hydrophobicity of the groups on the PAs induced aggregation, whereas suspensions of NPsgrafted by DEPA remained stable up to the highestr . Unexpectedly, CAPA-modified NPs showedaggregation even at low r, suggesting that the carboxylic end group was also grafted to the surface. Surface modification of aqueous sols with PAs allows thus for the grafting of a higher density and a wider variety of organic groups than organosilanes, offering an increased control of the interactions between NPs, which is of interest for designing waterborne nanocomposites.