Einstein-Katz action, variational principle, Noether charges and the thermodynamics of AdS-black holes

In this paper we describe 4-dimensional gravity coupled to scalar and Maxwell fields by the Einstein-Katz action, that is, the covariant version of the "Gamma-Gamma $-$ Gamma-Gamma" part of the Hilbert action supplemented by the divergence of a generalized "Katz vector". We consider static solutions of Einstein's equations, parametrized by some integration constants, which describe an ensemble of asymptotically AdS black holes. Instead of the usual Dirichlet boundary conditions, which aim at singling out a specific solution within the ensemble, we impose that the variation of the action vanishes on shell for the broadest possible class of solutions. We will see that, when a long-range scalar "hair" is present, only sub-families of the solutions can obey that criterion. The Katz-Bicak-Lynden-Bell ("KBL") superpotential built on this (generalized) vector will then give straightforwardly the Noether charges associated with the spacetime symmetries (that is, in the static case, the mass). Computing the action on shell, we will see next that the solutions which obey the imposed variational principle, and with Noether charges given by the KBL superpotential, satisfy the Gibbs relation, the Katz vectors playing the role of "counterterms". Finally, we show on the specific example of dyonic black holes that the sub-class selected by our variational principle satisfies the first law of thermodynamics when their mass is defined by the KBL superpotential.Comment: Accepted for publication by JHE

Discrimination de courbes par régression inverse fonctionnelle

19 pagesNational audienceLes méthodes de régression inverse telles que la SIR (Li,1991) ont été développées dans le domaine de la régression multivariée pour éviter le célèbre fléau de la dimension. Elles ont été récemment étendues aux données fonctionnelles. Plusieurs approches ont été proposées et nous présentons ici un article de synthèse et de comparaison en abordant le cas où la variable réponse est un vecteur d'indicatrice d'appartenance à des classes. Nous montrons qu'alors la régression inverse conduit à une méthode de discrimination dont la pertinence est établie sur des données réelles et simulées

The weight of phonetic substance in the structure of sound inventories

In the research field initiated by Lindblom & Liljencrants in 1972, we illustrate the possibility of giving substance to phonology, predicting the structure of phonological systems with nonphonological principles, be they listener-oriented (perceptual contrast and stability) or speaker-oriented (articulatory contrast and economy). We proposed for vowel systems the Dispersion-Focalisation Theory (Schwartz et al., 1997b). With the DFT, we can predict vowel systems using two competing perceptual constraints weighted with two parameters, respectively λ and α. The first one aims at increasing auditory distances between vowel spectra (dispersion), the second one aims at increasing the perceptual salience of each spectrum through formant proximities (focalisation). We also introduced new variants based on research in physics - namely, phase space (λ,α) and polymorphism of a given phase, or superstructures in phonological organisations (Vallée et al., 1999) which allow us to generate 85.6% of 342 UPSID systems from 3- to 7-vowel qualities. No similar theory for consonants seems to exist yet. Therefore we present in detail a typology of consonants, and then suggest ways to explain plosive vs. fricative and voiceless vs. voiced consonants predominances by i) comparing them with language acquisition data at the babbling stage and looking at the capacity to acquire relatively different linguistic systems in relation with the main degrees of freedom of the articulators; ii) showing that the places “preferred” for each manner are at least partly conditioned by the morphological constraints that facilitate or complicate, make possible or impossible the needed articulatory gestures, e.g. the complexity of the articulatory control for voicing and the aerodynamics of fricatives. A rather strict coordination between the glottis and the oral constriction is needed to produce acceptable voiced fricatives (Mawass et al., 2000). We determine that the region where the combinations of Ag (glottal area) and Ac (constriction area) values results in a balance between the voice and noise components is indeed very narrow. We thus demonstrate that some of the main tendencies in the phonological vowel and consonant structures of the world’s languages can be explained partly by sensorimotor constraints, and argue that actually phonology can take part in a theory of Perception-for-Action-Control

Growth of the extremophilic Deinococcus geothermalis DSM 11302 using co-substrate fed-batch culture

Deinococcus geothermalis metabolism has been scarcely studied to date, although new developments on its utilization for bioremediation have been carried out. So, largescale production of this strain and a better understanding of its physiology are required. A fed-batch experiment was conducted to achieve a high cell density non-limiting culture of D. geothermalis DSM 11302. A co-substrate nutritional strategy using glucose and yeast extract was carried out in a 20-L bioreactor in order to maintain a non-limited growth at a maximal growth rate of 1 h−1 at 45 °C. Substrate supplies were adjusted by monitoring online culture parameters and physiological data (dissolved oxygen, gas analyses, respiratory quotient, biomass concentration). The results showed that yeast extract could serve as both carbon and nitrogen sources, although glucose and ammonia were consumed too. Yeast extract carbon-specific uptake rate reached a value 4.5 times higher than glucose carbon-specific uptake rate. Cell concentration of 9.6 g L−1 dry cell weight corresponding to 99 g of biomass was obtained using glucose and yeast extract as carbon and nitrogen sources

Lithium conducting solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 obtained via solution chemistry

NaSICON-type lithium conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) is synthesized with controlled grain size and composition using solution chemistry. After thermal treatment at 850 C, sub-micronic crystallized powders with high purity are obtained. They are converted into ceramic through Spark Plasma Sintering at 850–1000 C. By varying the processing parameters, pellet with conductivities up to 1.6 * 10−4 S/cm with density of 97% of the theoretical density have been obtained. XRD, FEG-SEM, ac-impedance and Vickers indentation were used to characterize the products. The influence of sintering parameters on pellet composition, microstructure and conductivity is discussed in addition to the analysis of the mechanical behavior of the grains interfaces

Plant and spider communities benefit differently from the presence of planted hedgerows in highway verges

International audienceRoad verges should play a crucial role as a refuge for native flora and fauna in human dominated landscapes. However, the influence of construction choices, such as plantation of woody species, on the biodiversity supported by roadsides has received little attention, although the presence of hedgerows in roadsides is likely to enhance their role as a refuge, notably for woodland species. Using standardised methods, we assessed the impact of planted hedgerows on two taxonomic groups (plants and spiders) inhabiting highway verges within an intensive agricultural landscape. We examined community richness, taxonomic and functional composition in sites with and without planted hedgerows. At the site level, the response of plant and spider communities to the presence of planted hedgerows differed markedly: hedgerows were associated with significantly higher plant richness (higher α-diversity), but similar spider richness. Plant communities in sites without hedgerows appeared as a subset of communities in sites with hedgerows, whereas spider communities in non-planted sites were complementary to that of planted sites (increased β-diversity). The presence of planted hedgerows was also associated with increased taxonomic and functional trait diversity at the landscape level (γ-diversity), through an increased β-diversity in both plants and spiders. Our results thus suggest that a mosaic of planted hedgerows and grassland habitats is crucial for the maintenance of biodiversity at a landscape scale. By providing information for road practitioners and policy makers regarding their potential impact on biodiversity, these results have important direct implications for the management of road networks

Passive tomography for elastic waves in solids

In this paper we derive relations between the cross-correlation of ambient noises recorded at two different points and the Green's function of the elastic waves in a medium with viscous damping. The Green's function allows to estimate physical parameters such as speeds or distances. Furthermore, this work is extended by introducing the Green's correlation function proposed by J-L. Lacoume in [Lacoume07]. Some recent works proved the possible reconstruction of the Green's function for scalar waves from the cross-correlation function of ambient noise. In this work, we consider vector waves propagating in a three dimensional solid medium. Two approaches are developed. Firstly, we extend theoretical derivations proposed by Y. Colin de Verdi`ere in [ColinDeVerdiere09], relating cross-correlation of scalar waves to 1D Green's function using linear operator theory. The second approach recasts the three dimensional problem in the framework of Fourier theory. This allows to improve physical understanding of the underlying physical processes as outlined in [Lacoume07].Comment: 24 page