Holography of the N=1 Higher-Spin Theory on AdS4

We argue that the N=1 higher-spin theory on AdS4 is holographically dual to the N=1 supersymmetric critical O(N) vector model in three dimensions. This appears to be a special form of the AdS/CFT correspondence in which both regular and irregular bulk modes have similar roles and their interplay leads simultaneously to both the free and the interacting phases of the boundary theory. We study various boundary conditions that correspond to boundary deformations connecting, for large-N, the free and interacting boundary theories. We point out the importance of parity in this holography and elucidate the Higgs mechanism responsible for the breaking of higher-spin symmetry for subleading N.Comment: 19 page

Holography and Quaternionic Taub-NUT

As a concrete application of the holographic correspondence to manifolds which are only asymptotically Anti-de Sitter, we take a closer look at the quaternionic Taub-NUT space. This is a four dimensional, non-compact, inhomogeneous, riemannian manifold with the interesting property of smoothly interpolating between two symmetric spaces, AdS_4 itself and the coset SU(2,1)/U(2). Even more interesting is the fact that the scalar curvature of the induced conformal structure at the boundary (corresponding to a squashed three-sphere) changes sign as we interpolate between these two limiting cases. Using twistor methods, we construct the bulk-to-bulk and bulk-to-boundary propagators for conformally coupled scalars on quaternionic Taub-NUT. This may eventually enable us to calculate correlation functions in the dual strongly coupled CFT on a squashed S^3 using the standard AdS/CFT prescription.Comment: 1+36 pages, no figures. Some minor typos correcte

Étude des équilibres des phases dans le système Ag-Sn-In à 280 °C

The Ag-Sn system is among the most studied ones in the prospective of the abandon of the lead containing alloys. On the other hand the temperatures of these alloys are higher than those of the now used Pb-Sn eutectic alloys. Consecutively the addition of In – a low melting element is interesting from the new materials’ development. The isothermal section of the Ag-Sn-In system at 280°C was studied by using optical and scanning electron (SEM) microscopies, X-ray diffraction, differential scanning calorimetry (DSC) and Vickers’ microhardness measurements. The microhardness values of $\alpha$(Ag), $\epsilon$(Ag$_4$Sn) and $\zeta$ phases were measured. The ternary eutectic‘s position reported in the literature was confirmed. The respective third element’s solubilities were determined.Le système Ag-Sn est parmi les systèmes les plus étudiés dans la perspective de l'abandon des alliages à base de Pb. D'autre part les températures de fusion de ces alliages sont plus élevées que celle de l'eutectique Pb-Sn actuellement employé. Consécutivement, l'addition d'indium, un élément ayant température de fusion relativement basse, est un moyen intéressant pour la mise au point de nouvelles brasures. La coupe isotherme du système Ag-Sn-In à 280°C a été construite à l'aide des microscopies optique et électronique à balayage (MEB), de la diffraction des rayons X, de mesures de microdureté Vickers et de calorimétrie différentielle à balayage (DSC). Les microduretés des phases $\alpha$(Ag), $\epsilon$(Ag$_4$Sn) et $\zeta$ ont été mesurées. La position de l'eutectique ternaire rapportée antérieurement dans la littérature a été confirmée. Les solubilités du troisième élément respectif ont été déterminées

Étude expérimentale du système Sn-Ti-Zn à 600 °C

The interest towards the new lead-free solders becomes important in view of the prohibition of lead solders. Multiple substituting materials are presently at study. Tin and zinc are often constituents of various potential solders. Further, the additions of Ti in the binary systems improve the mechanical properties and alloys’ wetting. The isothermal section of the Sn-Ti-Zn system was studied using scanning electron microscopy, X-ray diffraction, and metallographic methods. An important result of this work is the discovery of a formerly unknown ternary compound. The statistical treatment of the obtained data gives compositions between Sn$_4$Ti$_5$Zn$_11$ and SnTiZn$_2$.L'intérêt des alliages de brasure sans plomb devient important dans la perspective d’interdiction des brasures au plomb. De nombreux matériaux de substitution sont actuellement à l'étude. L'étain et le zinc sont souvent utilisés dans les alliages de brasures potentiels. Par ailleurs, en général, les additions de Ti dans les systèmes binaires entraînent une amélioration des propriétés mécaniques et de la mouillabilité des alliages. La coupe isotherme du système Sn-Ti-Zn a été étudiée, en utilisant la diffraction des rayons X, la microscopie électronique à balayage et les méthodes métallographiques. Un résultat important de cette étude est la découverte d'un composé ternaire, inconnu auparavant. Le traitement statistique des données situe la composition entre Sn$_4$Ti$_5$Zn$_11$ et SnTiZn$_2$