BPS Amplitudes, Helicity Supertraces and Membranes in M-Theory

We study BPS dominated loop amplitudes in M-theory on T^2. For this purpose we generalize the concept of helicity supertraces to nine spacetime dimensions. These traces distinguish between various massive supermultiplets and appear as coefficients in their one-loop contributions to n-graviton scattering amplitudes. This can be used to show that only ultrashort BPS multiplets contribute to the R^4 term in the effective action, which was first computed by Green, Gutperle and Vanhove. There are two inequivalent ultrashort BPS multiplets which describe the Kaluza-Klein states and the wrapped membranes that cover the torus a number of times. From the perspective of the type-II strings they correspond to momentum and winding states and D0 or D1 branes.Comment: 15 page

Symmetries of Lagrangian fibrations

We construct fiber-preserving anti-symplectic involutions for a large class of symplectic manifolds with Lagrangian torus fibrations. In particular, we treat the K3 surface and the quintic threefold. We interpret our results as corroboration of the view that in homological mirror symmetry, an anti-symplectic involution is the mirror of duality. In the same setting, we construct fiber-preserving symplectomorphisms that can be interpreted as the mirror to twisting by a holomorphic line bundle.Comment: 45 page

Les représentations de la description de personnages dans l'écriture d'un récit d'aventures chez les élèves de première secondaire

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

La construction des barrages au Québec, 1898 à 1963 : un essai sur l'évolution des techniques et sur la place des ingénieurs francophones

Québec Université Laval, Bibliothèque 201