Dark Energy as a Born-Infeld Gauge Interaction Violating the Equivalence Principle

We investigate the possibility that dark energy does not couple to gravitation in the same way than ordinary matter, yielding a violation of the weak and strong equivalence principles on cosmological scales. We build a transient mechanism in which gravitation is pushed away from general relativity by a Born-Infeld gauge interaction acting as an "Abnormally Weighting" (dark) Energy. This mechanism accounts for the Hubble diagram of far-away supernovae by cosmic acceleration and time variation of the gravitational constant while accounting naturally for the present tests on general relativity.Comment: 5 pages, 3 figures, sequel of Phys. Rev. D 73 023520 (2006), to appear in Physical Review Letter

Rippled Cosmological Dark Matter from Damped Oscillating Newton Constant

Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its General Relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation -> dark matter -> dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the General Relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favorably examined.Comment: RevTex4, 12 pages, 5 figures; Minor revision, References adde

Cosmological test of the Yilmaz theory of gravity

We test the Yilmaz theory of gravitation by working out the corresponding Friedmann-type equations generated by assuming the Friedmann-Robertson-Walker cosmological metrics. In the case that space is flat the theory is consistent only with either a completely empty universe or a negative energy vacuum that decays to produce a constant density of matter. In both cases the total energy remains zero at all times, and in the latter case the acceleration of the expansion is always negative. To obtain a more flexible and potentially more realistic cosmology, the equation of state relating the pressure and energy density of the matter creation process must be different from the vacuum, as for example is the case in the steady-state models of Gold, Bondi, Hoyle and others. The theory does not support the cosmological principle for curved space K =/= 0 cosmological metrics

Photoactivatable genetically encoded calcium indicators for targeted neuronal imaging.

Circuit mapping requires knowledge of both structural and functional connectivity between cells. Although optical tools have been made to assess either the morphology and projections of neurons or their activity and functional connections, few probes integrate this information. We have generated a family of photoactivatable genetically encoded Ca(2+) indicators that combines attributes of high-contrast photolabeling with high-sensitivity Ca(2+) detection in a single-color protein sensor. We demonstrated in cultured neurons and in fruit fly and zebrafish larvae how single cells could be selected out of dense populations for visualization of morphology and high signal-to-noise measurements of activity, synaptic transmission and connectivity. Our design strategy is transferrable to other sensors based on circularly permutated GFP (cpGFP)

Bowhead Whale (Balaena mysticetus) Feeding near Point Barrow, Alaska, During the 1985 Spring Migration

Examination of stomach contents and behavioral observations showed conclusively that bowhead whales were feeding in the Point Barrow area during the spring of 1985. All three bowheads harvested near the village of Barrow had over five litres of pelagic zooplankton (calanoid copepods and euphausiids) in their stomachs. Over 60 whales were observed during the period 26 May through 6 June diving repeatedly under the landfast ice and feeding in an area 11.2 km southwest of Point Barrow. Observers recorded times for dive, surfacing and respiration intervals for these whales. The recorded times were significantly different from those of bowhead whales migrating past Point Barrow in the spring and from bowheads, whose major activity was feeding, recorded in the Canadian Beaufort Sea during the summer and fall.Key words: Balaena mysticetus, Point Barrow, feeding, bowhead whale, behavior, copepod,  euphausiid, respiration, springUn examen du contenu stomacal de baleines franches et des observations de leur comportement ont montré sans aucun doute qu’elles se nourrissaient dans la zone de Point Barrow pendant le printemps de1985. Les trois baleines franches pêchées près du village de Barrow avaient toutes dans l’estomac plus de cinq litres de zooplancton pélagique (copépodes calanoïdes et euphausiacés). Pendant la période allant du 26 mai au 6 juin, on a observé plus de 60 baleines qui plongeaient de façon répétée sous la banquise côtière pour se nourrir dans une zone située à 11,2 km au sud-ouest de Point Barrow. Les observateurs ont noté le moment de la plongée et celui du retour à la surface, et l’intervalle entre les souffles des baleines. Les durées enregistrées étaient nettement différentes de celles mesurées pour des baleines franches qui passaient à Point Barrow pendant leur migration au printemps, et de celles enregistrées dans la mer de Beaufort canadienne en été et en automne pour des baleines franches dont l’activité principale était de se nourrir.Mots clés: Balaena mysticetus, Point Barrow, se nourrir, baleine franche, comportement, copépode, euphausiacé, respiration, printemp

Effectively four-dimensional spacetimes emerging from d=5 Einstein-Gauss-Bonnet Gravity

Einstein-Gauss-Bonnet gravity in five-dimensional spacetime provides an excellent example of a theory that, while including higher-order curvature corrections to General Relativity, still shares many of its features, such as second-order field equations for the metric. We focus on the largely unexplored case where the coupling constants of the theory are such that no constant-curvature solution is allowed, leaving open the question of what the vacuum state should then be. We find that even a slight deviation from the anti-de Sitter Chern-Simons theory, where the vacuum state is five-dimensional AdS spacetime, leads to a complete symmetry breakdown, with the fifth dimension either being compactified into a small circle or shrinking away exponentially with time. A complete family of solutions, including duality relations among them, is uncovered and shown to be unique within a certain class. This dynamical dimensional reduction scenario seems particularly attractive as a means for higher-dimensional theories to make contact with our four-dimensional world.Comment: 9 pages, 4 figures. v2: New section on geometrical significance of solutions. Final version for CQ

Perserverance measures and attainment in first year computing science students.

We investigate the link between concepts of perseverance such as conscientiousness and grit, and the academic attainment of first year computing students. We review the role that perseverance plays in learning models, as well as describing the trait of conscientiousness in the Five Factor Model of personality. We outline research that links this trait with academic success, before focussing on more recent, narrower conceptualisations of perseverance such as academic tenacity and grit. We describe one of the questionnaire tools that have been used to assess the construct of grit. We give details of an investigation that looked for correlations between student responses to Duckworth's Grit Survey, the Big Five Inventory (BFI) Personality Survey and summative attainment scores in a first year programming course. The results suggest a weak but significant correlation between conscientiousness, grit and programming achievement. We discuss these results as well as the limitations of the method used. Finally, we make some observations about the importance of these concepts in Computer Science education and outline further work in this area

Dynamic Provenance for SPARQL Update

While the Semantic Web currently can exhibit provenance information by using the W3C PROV standards, there is a "missing link" in connecting PROV to storing and querying for dynamic changes to RDF graphs using SPARQL. Solving this problem would be required for such clear use-cases as the creation of version control systems for RDF. While some provenance models and annotation techniques for storing and querying provenance data originally developed with databases or workflows in mind transfer readily to RDF and SPARQL, these techniques do not readily adapt to describing changes in dynamic RDF datasets over time. In this paper we explore how to adapt the dynamic copy-paste provenance model of Buneman et al. [2] to RDF datasets that change over time in response to SPARQL updates, how to represent the resulting provenance records themselves as RDF in a manner compatible with W3C PROV, and how the provenance information can be defined by reinterpreting SPARQL updates. The primary contribution of this paper is a semantic framework that enables the semantics of SPARQL Update to be used as the basis for a 'cut-and-paste' provenance model in a principled manner.Comment: Pre-publication version of ISWC 2014 pape