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We study the one-dimensional totally asymmetric simple exclusion process in contact with two reservoirs including also a fugacity at one boundary. The eigenvectors and the eigenvalues of the corresponding Markov matrix are computed using the modified algebraic Bethe ansatz, method introduced recently to study the spin chain with non-diagonal boundaries. We provide in this case a proof of this method.

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The existence of two independent filler-dependent high-temperature Maxwell–Wagner–Sillars (MWS) dielectric processes is demonstrated and characterized in detail in silica-filled styrene–butadiene (SB) industrial nanocomposites of simplified composition using Broadband Dielectric Spectroscopy (BDS). The uncrosslinked samples are made with 140 kg/mol SB-chains, half of which carry a single graftable end-function (50% D3), and Zeosil 1165 MP silica incorporated by solid-phase mixing. While one high-temperature process is known to exist in other systems, the dielectric properties of a new silica-related process – strength, relaxation time, and activation energy – have been evidenced and described as a function of silica volume fraction and temperature. In particular, it is shown that its strength follows a percolation behavior as observed with the ionic conductivity and rheology. Moreover, activation energies show the role of polymer layers separating aggregates even when they are percolated. Apart from simultaneous characterization over a broad frequency range up to local polymer and silanol dynamics, it is believed that such high-temperature BDS-measurements can thus be used to detect reorganizations in structurally-complex silica nanocomposites. Moreover, they should contribute to a better identification of dynamical processes via the described sensitivity to structure in such systems.

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The collision of a liquid drop against a small target results in the formation of a thin liquid sheet that extends radially until it reaches a maximum diameter. The subsequent retraction is due to the air-liquid surface tension. We have used a time- and space-resolved technique to measure the thickness field of this class of liquid sheet, based on the grey level measurement of the image of a dyed liquid sheet recorded using a fast camera. This method enables a precise measurement of the thickness in the range $(10-450) \, \mathrm{\mu m}$, with a temporal resolution equal to that of the camera. We have measured the evolution with time since impact, $t$, and radial position, $r$, of the thickness, $h(r,t)$, for various drop volumes and impact velocities. Two asymptotic regimes for the expansion of the sheet are evidenced. The scalings of the thickness with $t$ and $r$ measured in the two regimes are those that were predicted in \citet{Rozhkov2004} fort the short-time regime and \citet{Villermaux2011} for the long time regime, but never experimentally measured before. Interestingly, our experimental data also evidence the existence of a maximum of the film thickness $h_{\rm{max}}(r)$ at a radial position $r_{\rm{h_{max}}}(t)$ corresponding to the crossover of these two asymptotic regimes. The maximum moves with a constant velocity of the order of the drop impact velocity, as expected theoretically. Thanks to our visualization technique, we also evidence an azimuthal thickness modulation of the liquid sheets.

Commentaires: accepted for publication in Journal of Fluid Mechanics. Réf Journal: J. Fluid Mech. (2015), vol. 764, pp. 428-444

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We analyze the first-order formulation of the ghost-free bigravity model in three-dimensions known as zwei-dreibein gravity. For a special choice of parameters, it was argued to have an additional gauge symmetry and give rise to a partially massless theory. We provide a thorough canonical analysis and identify that whether the theory becomes partially massless depends on the form of the stability condition of the secondary constraint responsible for the absence of the ghost. Generically, it is found to be an equation for a Lagrange multiplier implying that partially massless zwei-dreibein gravity does not exist. However, for special backgrounds this condition is identically satisfied leading to the presence of additional symmetries, which however disappear at quadratic order in perturbations.

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This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb$^{-1}$. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of $\sigma_s$=5.0$\pm$4.3 pb, consistent with the Standard Model expectation.

Commentaires: 10 pages plus author list plus cover page (26 pages total), 3 figures, 2 tables, submitted to Phys. Lett. B. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2014-03/ ; See paper for full list of authors