On ADE Quiver Models and F-Theory Compactification

Based on mirror symmetry, we discuss geometric engineering of N=1 ADE quiver models from F-theory compactifications on elliptic K3 surfaces fibered over certain four-dimensional base spaces. The latter are constructed as intersecting 4-cycles according to ADE Dynkin diagrams, thereby mimicking the construction of Calabi-Yau threefolds used in geometric engineering in type II superstring theory. Matter is incorporated by considering D7-branes wrapping these 4-cycles. Using a geometric procedure referred to as folding, we discuss how the corresponding physics can be converted into a scenario with D5-branes wrapping 2-cycles of ALE spaces.Comment: 21 pages, Latex, minor change

Super Calabi-Yau's and Special Lagrangians

We apply mirror symmetry to the super Calabi-Yau manifold CP^{(n|n+1)} and show that the mirror can be recast in a form which depends only on the superdimension and which is reminiscent of a generalized conifold. We discuss its geometrical properties in comparison to the familiar conifold geometry. In the second part of the paper examples of special-Lagrangian submanifolds are constructed for a class of super Calabi-Yau's. We finally comment on their infinitesimal deformations.Comment: 20 pages, no figures, latex; v2: references added; v3: minor clarifications added, version published in JHE

On Black Attractors in 8D and Heterotic/Type IIA Duality

Motivated by the study of black attractors in 8D supergravity with 16 supersymmetries, we use the field theory approach and 8D supersymmetry with non trivial central charges to shed light on the exact duality between heterotic string on T^2 and type IIA on real connected and compact surfaces {\Sigma}2. We investigate the two constraints that should be obeyed by {\Sigma}2 and give their solutions in terms of intersecting 2-cycles as well their classification using Dynkin diagrams of affine Kac-Moody algebras. It is shown as well that the moduli space of these dual theories is given by SO(1,1)x((SO(2,r+2))/(SO(2)xSO(r+2))) where r stands for the rank of the gauge symmetry G_{r} of the 10D heterotic string on T^2. The remarkable cases r=-2,-1,0 as well as other features are also investigated.Comment: LaTex, 18 pages, 2 figures, To appear in JHE

Effet de l’hydratation et du rapport E/C sur les paramètres de la rugosité de surface de pâtes cimentaires

Ce travail s'inscrit dans le cadre du projet national à Fond Unique Interministériel, nommé ERGOFORM (ERGOnomic FORMwork-Système de coffrage auto-stable diminuant la pénibilité de chantier), qui vise à mettre au point un procédé de coffrage innovant. Quatre pâtes de ciment ont été élaborées avec des rapports Eau sur Ciment (E/C) de respectivement 0,30, 0,35, 0,40 et 0,45. L'évolution des propriétés physiques et mécaniques des pâtes de ciment ont été mesurées : la porosité accessible à l'eau sous vide, les résistances à la compression et en flexion trois points. L'évolution des paramètres de rugosité en fonction du temps de cure a été analysée par microscopie interférométrique et microscopie électronique à balayage environnemental (MEB-E). Les résultats expérimentaux montrent que l'augmentation du dosage en ciment diminue la porosité accessible à l'eau et améliore les propriétés mécaniques à 24h (après décoffrage nommé T0). L'évolution de la porosité en fonction du temps de cure montre une augmentation se stabilisant après 4 jours d'immersion dans l'eau pour les pâtes cimentaires de rapports E/C de 0,40 et de 0,45 (Groupe 2). En revanche, cette augmentation se prolonge légèrement pour les pâtes de ciment 0,30 et 0,35 (Groupe 1). Par ailleurs, l'évolution des paramètres de rugosité est fonction du dosage en ciment. En effet, les analyses microscopiques et par diffraction des rayons X mettent en évidence une diminution de la quantité des pores en surface, mais aussi l'évolution des paramètres de rugosité par un changement de sa morphologie et la formation de portlandite même après 2 heures de cure normalisée. : The experimental study is part of the national project ERGOnomic FORMwork (Self-Stable Formwork System Reducing Site Difficulty) named ERGOFORM, which aims to develop an innovative formwork process for construction field. Four cement pastes were provided with different water-to-cement ratio (W/C), respectively, 0.30, 0.35, 0.40 and 0.45. The evolution of physical and mechanical properties of cement pastes was measured through water porosity under vacuum, compressive strength and flexural strength. The variation of the roughness parameters was performed by the interferometry microscope. The environmental scanning electron microscopy (E-SEM) was used to analyze the evolution of the surface morphology. The experimental results show that the increase of cement quantity decreases the water porosity and improves the mechanical properties of studied mix designs at 24 hours (after stripping, called T0). The evolution of porosity versus curing time shows that the variation stabilizes after 4 days of immersion in water for the ratio W/C 0.40 and 0.45, named G2 (Group 2). On the other hand, this variation slightly continued for cement pastes 0.30 and 0.35, named G1 (Group 1). Moreover, the evolution of roughness parameters is dependent on cement quantity in mix design. Indeed, the MEB coupling EDX and X-ray diffraction analyzes reveal a decrease in the amount of surface pores, but also the evolution of the roughness parameters by a change in its morphology and the formation of portlandite even after 2 hours of standardized cure

The dimer-monomer equilibrium of SARS-CoV-2 main protease is affected by small molecule inhibitors

The maturation of coronavirus SARS-CoV-2, which is the etiological agent at the origin of the COVID-19 pandemic, requires a main protease Mpro to cleave the virus-encoded polyproteins. Despite a wealth of experimental information already available, there is wide disagreement about the Mpro monomer-dimer equilibrium dissociation constant. Since the functional unit of Mpro is a homodimer, the detailed knowledge of the thermodynamics of this equilibrium is a key piece of information for possible therapeutic intervention, with small molecules interfering with dimerization being potential broad-spectrum antiviral drug leads. In the present study, we exploit Small Angle X-ray Scattering (SAXS) to investigate the structural features of SARS-CoV-2 Mpro in solution as a function of protein concentration and temperature. A detailed thermodynamic picture of the monomer-dimer equilibrium is derived, together with the temperature-dependent value of the dissociation constant. SAXS is also used to study how the Mpro dissociation process is affected by small inhibitors selected by virtual screening. We find that these inhibitors affect dimerization and enzymatic activity to a different extent and sometimes in an opposite way, likely due to the different molecular mechanisms underlying the two processes. The Mpro residues that emerge as key to optimize both dissociation and enzymatic activity inhibition are discussed

The Supermembrane with Central Charges on a G2 Manifold

We construct the 11D supermembrane with topological central charges induced through an irreducible winding on a G2 manifold realized from the T7/Z2xZ2xZ2 orbifold construction. The hamiltonian H of the theory on a T7 target has a discrete spectrum. Within the discrete symmetries of H associated to large diffeomorphisms, the Z2xZ2xZ2 group of automorphisms of the quaternionic subspaces preserving the octonionic structure is relevant. By performing the corresponding identification on the target space, the supermembrane may be formulated on a G2 manifold, preserving the discretness of its supersymmetric spectrum. The corresponding 4D low energy effective field theory has N=1 supersymmetry.Comment: Reviewed version. spectral propertis discussed, two more sections added, 27 pages,Late

The Topological B-model on a Mini-Supertwistor Space and Supersymmetric Bogomolny Monopole Equations

In the recent paper hep-th/0502076, it was argued that the open topological B-model whose target space is a complex (2|4)-dimensional mini-supertwistor space with D3- and D1-branes added corresponds to a super Yang-Mills theory in three dimensions. Without the D1-branes, this topological B-model is equivalent to a dimensionally reduced holomorphic Chern-Simons theory. Identifying the latter with a holomorphic BF-type theory, we describe a twistor correspondence between this theory and a supersymmetric Bogomolny model on R^3. The connecting link in this correspondence is a partially holomorphic Chern-Simons theory on a Cauchy-Riemann supermanifold which is a real one-dimensional fibration over the mini-supertwistor space. Along the way of proving this twistor correspondence, we review the necessary basic geometric notions and construct action functionals for the involved theories. Furthermore, we discuss the geometric aspect of a recently proposed deformation of the mini-supertwistor space, which gives rise to mass terms in the supersymmetric Bogomolny equations. Eventually, we present solution generating techniques based on the developed twistorial description together with some examples and comment briefly on a twistor correspondence for super Yang-Mills theory in three dimensions.Comment: 55 pages; v2: typos fixed, published versio