L'acquisition de la négation en français par des adultes arabophones

International audienceThis paper is devoted to an empirical study of the acquisition of neagtion in French L2 by 6 adult Moroccans. The study focusses on two negators non(no) and pas (not) nd on two main informants. It is shown that the development of negator non and negator pasfollow different paths. The use of negator non seems to be determined by pargamtic factors whereas the use of negator pas is related to grammatical factors. The informants of this study show a certain measure of variability in the acquisition of nagation in French. Only one informant seems to use pre-verbal negation in the early stages of his learner variety. The study is not able to back up the claim of L1 transfer in the acquisition of negation in L2.Cet article fournit une description des itinéraires d'appropriation de la négation en français L2 par 6 adultes marocains. Deux marques de la négation sont privilégiés : non et pas, et l'étude se concentre sur les productions de 2 informateurs marocains essentiellement. Il apparaît que l'emploi de non et de pas obéit à des contraintes différentes ; l'emploi de la première marque semble être déterminé par des facteurs pragmatiques alors que l'usage du deuxième négateur est davantage déterminé par des considérations grammaticales. Les informateurs étudiés présentent une relative diversité de parcours dans l'appropriation de la négation en L2 ; un seul informateur privilégie nettement l'emploi d'une négation pré-prédicative dans les premières phases de sa variété d'apprenant. L'étude n'est pas en mesure de conclure à une influence décisive de la L1 dans l'emploi de la négation en L2

A study of online and blockwise updating of the EM algorithm for Gaussian mixtures.

A variant of the EM algorithm for the estimation of multivariate Gaussian mixtures, which allows for online as well as blockwise updating of sequentially obtained parameter estimates, is investigated. Several dierent update schemes are considered and compared, and the benets of articially performing EM in batches, even though all data are available, are discussed

E7(7) constraints on counterterms in N=8 supergravity

We prove by explicit computation that 6-point matrix elements of D^4R^4 and D^6R^4 in N=8 supergravity have non-vanishing single-soft scalar limits, and therefore these operators violate the continuous E7(7) symmetry. The soft limits precisely match automorphism constraints. Together with previous results for R^4, this provides a direct proof that no E7(7)-invariant candidate counterterm exists below 7-loop order. At 7-loops, we characterize the infinite tower of independent supersymmetric operators D^4R^6, R^8, phi^2 R^8,... with n>4 fields and prove that they all violate E7(7) symmetry. This means that the 4-graviton amplitude determines whether or not the theory is finite at 7-loop order. We show that the corresponding candidate counterterm D^8R^4 has a non-linear supersymmetrization such that its single- and double-soft scalar limits are compatible with E7(7) up to and including 6-points. At loop orders 7, 8, 9 we provide an exhaustive account of all independent candidate counterterms with up to 16, 14, 12 fields, respectively, together with their potential single-soft scalar limits.Comment: 9 pages, 1 table. Reference added, minor clarifications in abstract, typos correcte

Bivariate estimation of distribution algorithms for protein structure prediction.

A real-valued bivariate ‘Estimation of Distribution Algorithm’ specific for the ab initio and full-atom Protein Structure Prediction problem is proposed. It is known that this is a multidimensional and multimodal problem. In order to deal with the multimodality and the correlation of dihedral angles φ and ψ, we developed approaches based on Kernel Density Estimation and Finite Gaussian Mixtures. Simulation results have shown that both techniques are promising when applied to that problem

Note on graviton MHV amplitudes

Two new formulas which express n-graviton MHV tree amplitudes in terms of sums of squares of n-gluon amplitudes are discussed. The first formula is derived from recursion relations. The second formula, simpler because it involves fewer permutations, is obtained from the variant of the Berends, Giele, Kuijf formula given in Arxiv:0707.1035.Comment: 10 page

Generating Tree Amplitudes in N=4 SYM and N=8 SG

We study n-point tree amplitudes of N=4 super Yang-Mills theory and N=8 supergravity for general configurations of external particles of the two theories. We construct generating functions for n-point MHV and NMHV amplitudes with general external states. Amplitudes derived from them obey SUSY Ward identities, and the generating functions characterize and count amplitudes in the MHV and NMHV sectors. The MHV generating function provides an efficient way to perform the intermediate state helicity sums required to obtain loop amplitudes from trees. The NMHV generating functions rely on the MHV-vertex expansion obtained from recursion relations associated with a 3-line shift of external momenta involving a reference spinor |X]. The recursion relations remain valid for a subset of N=8 supergravity amplitudes which do not vanish asymptotically for all |X]. The MHV-vertex expansion of the n-graviton NMHV amplitude for n=5,6,...,11 is independent of |X] and exhibits the asymptotic behavior z^{n-12}. This presages difficulties for n > 12. Generating functions show how the symmetries of supergravity can be implemented in the quadratic map between supergravity and gauge theory embodied in the KLT and other similar relations between amplitudes in the two theories.Comment: 53 pages, 8 figures. v2: Added references, typos correcte

Holography for N=2∗{\cal N}=2^* on S4S^4

We find the gravity dual of $\mathcal{N}=2^*$ super-Yang-Mills theory on $S^4$ and use holography to calculate the universal contribution to the corresponding $S^4$ free energy at large $N$ and large 't Hooft coupling. Our result matches the expression previously computed using supersymmetric localization in the field theory. This match represents a non-trivial precision test of holography in a non-conformal, Euclidean signature setting.Comment: 31 pages + appendices, 3 figure

Anomaly Cancellation in Supergravity with Fayet-Iliopoulos Couplings

We review and clarify the cancellation conditions for gauge anomalies which occur when N=1, D=4 supergravity is coupled to a Kahler non-linear sigma-model with gauged isometries and Fayet-Iliopoulos couplings. For a flat sigma-model target space and vanishing Fayet-Iliopoulos couplings, consistency requires just the conventional anomaly cancellation conditions. A consistent model with non-vanishing Fayet-Iliopoulos couplings is unlikely unless the Green-Schwarz mechanism is used. In this case the U(1) gauge boson becomes massive and the D-term potential receives corrections. A Green-Schwarz mechanism can remove both the abelian and certain non-abelian anomalies in models with a gauge non-invariant Kahler potential.Comment: 27 page

A study of online and blockwise updating of the EM algorithm for Gaussian mixtures

A variant of the EM algorithm for the estimation of multivariate Gaussian mixtures, which allows for online as well as blockwise updating of sequentially obtained parameter estimates, is investigated. Several dierent update schemes are considered and compared, and the benets of articially performing EM in batches, even though all data are available, are discussed