Consistent couplings between fields with a gauge freedom and deformations of the master equation

The antibracket in the antifield-BRST formalism is known to define a map Hp × Hq → Hp + q + 1 associating with two equivalence classes of BRST invariant observables of respective ghost number p and q an equivalence class of BRST invariant observables of ghost number p + q + 1. It is shown that this map is trivial in the space of all functionals, i.e. that its image contains only the zeroth class. However, it is generically non-trivial in the space of local functionals. Implications of this result for the problem of consistent interactions among fields with a gauge freedom are then drawn. It is shown that the obstructions to constructing non-trivial such interactions lie precisely in the image of the antibracket map and are accordingly non-existent if one does not insist on locality. However consistent local interactions are severely constrained. The example of the Chern-Simons theory is considered. It is proved that the only consistent, local, Lorentz covariant interactions for the abelian models are exhausted by the non-abelian Chern-Simons extensions. © 1993.

Brackets in the jet-bundle approach to field theory

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Catalogue de la bibliothéque ...

Vols. 1-2: Dressé par C. Ekama; v. 3, par G. C.Bohnensieg; v. 4, par J. J. Verwijnen.

Determinationofgroundwatermercury(II)contentusingadisposable goldmodified screenprintedcarbonelectrode

Mercury (II)measurementswereperformedthankstoanewlydevelopedelectrochemicalmethodusinga disposablegoldmodified screenprintedcarbonelectrode.Themethodhasawidedynamicrange(1–100 mg/L), agoodaccuracyandalimitofdetectionincompliancewithWHOstandards.Theapplicationofthe methodtoseveralgroundwatersamplesmadeitpossibletoidentify,forthe first time,mercurycontent higherthantherecommendedWHOstandardvalueinagoldminingactivityareainthenorthern partofBurkinaFaso.TheaccuracyoftheassaywascheckedbyICP/MS.

Surface enrichment in gold/silver alloys: effects of temperature studied by atom probe tomography

Bimetallic alloys are increasingly used in heterogeneous catalysis. This interest is explained by the emergence of new features that are absent in the parent single metals. Synergistic effects between the two combined elements create a more efficient catalyst. One of the most challenging aspect of multicomponent materials in catalysis is the ability to fine-tune the catalytic properties of an alloy by controlling the nature and composition of the surface [1]. For example, the gold/silver alloy combines a high activity and a large selectivity for a broad range of oxidation reaction.It is well established that the surface composition of alloys may deviate from that of the bulk phase. Surface enrichment has also important consequences in some applications of heterogeneous catalysis. In some cases, the thermal and chemical treatments can lead to opposite trends regarding the nature of the metal prone to surface enrichment. Using atom probe tomography we aim to link the physicochemical conditions the composition of the very first atomic layers of bimetallic catalysts and eventually to fine-tune the catalytic features of the latter.

Catalytic CO2 hydrogenation: study at the molecular scale using field emission techniques

An accurate characterization of the rhodium specimen was obtained via FIM experiments. Reaction behaviors between H2 and CO2 were observed in FEM mode at 700 K. At this temperature, CO desorption occurs, preventing CO+H2 reaction. Surface is mainly recovered by oxygen; reaction with hydrogen occurs. Finally, we can identify the reaction as the Reverse Water Gas Shift.

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1868 (SER2,T3).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1878 (SER3,T1).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1863 (T3).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1863 (T4).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1874 (SER2,T8).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

Périodicité : Annuel

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1862 (T1).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1870 (SER2,T5).

Revue des sociétés savantes / publiée sous les auspices du Ministère de l'instruction publique et des cultes. Sciences mathématiques, physiques et naturelles

1862 (T2).