Toward the Gravity Dual of Heterotic Small Instantons

The question of what happens when the heterotic SO(32) instanton becomes small was answered sometime back by Witten. The heterotic theory develops an enhanced Sp(2k) gauge symmetry for k small instantons, besides the allowed SO(32) gauge symmetry. An interesting question now is to ask what happens when we take the large k limit. In this paper we argue that in some special cases, where Gauss' law allows the large k limit, the dynamics of the large k small instantons can be captured by a dual gravitational description. For the cases that we elaborate in this paper, the gravity duals are non-Kahler manifolds although in general they could be non-geometric. These small instantons are heterotic five-branes and the duality allows us to study the strongly coupled field theories on these five-branes. We review and elaborate on some of the recent observations pointing towards this duality, and argue that in certain cases the gauge/gravity duality may be understood as small instanton transitions under which the instantons smoothen out and consequently lose the Sp(2k) gauge symmetry. This may explain how branes disappear on the dual side and are replaced by fluxes. We analyse the torsion classes before and after the transitions, and discuss briefly how the ADHM sigma model and related vector bundles could be studied for these scenarios.Comment: 47 pages, 3 eps figures, LaTex, JHEP3 file; v2: Another consistency check added, typos corrected and a reference added; v3: Text expanded a bit, minor typos corrected and a few references updated. Final version to appear in Phys. Rev.

Enquête sur les petits lieux de vente du livre en Franche-Comté

L’enquête présentée ici s\u27est déroulée de décembre 2016 à septembre 2017. Les "Petits lieux de vente du livre" désignent des établissements de commerce de proximité dont le chiffre d’affaires réalisé par la vente de livres neufs représente moins de 50 % du CA total, dont les maisons de la presse. Sont exclus les musées ou offices de tourisme, dont les modèles économiques et les problématiques professionnelles paraissent trop éloignées de celles des points de vente indépendants. Grâce à cette étude, le Centre régional du livre en Franche-Comté et ses partenaires souhaitent connaître les lieux de vente physique du livre sur leur territoire et mieux appréhender les spécificités et besoins de ces petits lieux de vente. Quelle place occupe le livre dans ces commerces, y a-t-il des possibilités de renforcer la présence du livre dans ces lieux

Agrobacterium tumefaciens gene transfer to Casuarina glauca : a tropical nitrogen-fixing tree

Transgenic calli of the tropical tree #Casuarina glauca were produced using #Agrobacterium tumefaciens-mediated gene transfer. Hypocotyls, cotyledons and epicotyls were excised from 30-60-day old #Casuarina seedlings and cocultivated with #Agrobacterium strain C58C1(pGV2260) containing the binary vector BIN19GUSINT. Transformed calli were selected on nutrient medium supplemented with 0,5 microM NAA, 2,5 microM BA and 50 mg/l kanamycin. Some of the factors influencing T-DNA transfer to #C. glauca$ explants were studied. Optimal transformation rates were obtained when explants from 45-day old seedlings were cocultivated for 3 days in the presence of 25 microM acetosyringone. Transgenic buds differentiated on 10% of the calli grown on transformed epicotyls. Evidence for genetic transformation was obtained by beta-glucuronidase assay, PCR and Southern hybridization. (Résumé d'auteur

Non-Extremality, Chemical Potential and the Infrared limit of Large N Thermal QCD

Non-extremal solution with warped resolved-deformed conifold background is important to study the infrared limit of large N thermal QCD. Earlier works in this direction have not taken into account all the back-reactions on the geometry, namely from the branes, fluxes, and black-hole carefully. In the present work we make some progress in this direction by solving explicitly the supergravity equations of motions in the presence of the backreaction from the black-hole. The backreactions from the branes and the fluxes on the other hand and to the order that we study, are comparatively suppressed. Our analysis reveal, among other things, how the resolution parameter would depend on the horizon radius and how the RG flows of the coupling constants should be understood in these scenarios, including their effects on the background three-form fluxes. We also study the effect of switching on a chemical potential in the background and, in a particularly simplified scenario, compute the actual value of the chemical potential for our case.Comment: 61 pages, LaTex, 3 eps figures; v2: Some corrections done in sec 2.1 to sharpen the regime of validity of our results. Text expanded, typos corrected and minor corrections added to the other sections; v3: Text expanded at various places, typos corrected and references added. Final version to appear in Physical Review