Braneworlds scenarios in a gravity model with higher order spatial three-curvature terms

In this work we study a Horava-like five-dimensional model in the context of braneworld theory. To begin with, the equations of motion of such model are obtained and, within the realm of warped geometry, we show that the model is consistent if and only if $\lambda$ takes its relativistic value 1. Furthermore, since the first derivative of the warp factor is discontinuous over the branes, we show that the elimination of problematic terms involving the square of the warp factor second order derivatives are eliminated by imposing detailed balance condition in the bulk. Afterwards, the Israel's junction conditions are computed, allowing the attainment of an effective Lagrangian in the visible brane. In particular, for a (4+1)-dimensional Horava-like model defined in the bulk without cosmological constant, we show that the resultant effective Lagrangian in the brane corresponds to a (3+1)-dimensional Horava-like model with an emergent positive cosmological constant but without detailed balance condition. Now, restoration of detailed balance condition, at this time imposed over the brane, plays an interesting role by fitting accordingly the sign of the arbitrary constant $\beta$ that labels the extra terms in the model, insuring a positive brane tension and a real energy for the graviton within its dispersion relation. To end up with, the brane consistency equations are obtained and, as a result, we show that the detailed balance condition again plays an essential role in eliminating bad behaving terms and that the model admits positive brane tensions in the compactification scheme if, and only if, $\beta$ is negative, what is in accordance with the previous result obtained for the visible brane.Comment: 23 pages, 1 figure, title modifie

Shelf-Ocean material exchange influencing the Atlantic chemical composition off NW Iberian margin since the last glaciation

Rivers are the main conduit of sediment to the shelf. The basin geology, the drainage area and the discharge rate are the major factors that determine their sediment load (Milliman and Syvistski, 1992). Besides suspended particles, dissolved components may also give some information on the eroded crust. Sr isotopes in carbonate shells of biological organisms have been used to study, in the geological record, the influence exerted by the chemical weathering of the continental crust on the seawater composition (Macdougall, 1991). In this work, Sr isotope ratios obtained in tests of foraminifera representing the last 40 ka are presented and discussed in the scope of the palaeogeographical evolution of NW Iberia. This work aims to present and discuss the results of Sr isotope analyses (performed, by TIMS, in the Isotope Geology Laboratory of the University of Aveiro) of tests of two species of foraminifera, from nine samples taken along the OMEX core KC 024-19 (181 cm; 42°08’98’’N, 10°29´96’’W, and 2765m), collected in the Galicia Bank area, off Galicia. Taking into account that Sr contained in the carbonate tests is usually considered as preserving the signature of the contemporaneous seawater, one planktonic species (Globigerina bulloides) and one benthic species (Cibicides wuellerstorfi) were selected in order to try to detect Sr isotope variations both through time and between two different levels of the water column. The core age model, which records the last 40 ka, is based on a combination of oxygen isotope stratigraphy, eight AMS 14C datings and the synchronisation of the last four Heinrich Events in the Iberian Margin sedimentary records. As a whole, the obtained 87Sr/86Sr ratios vary between 0.709209 and 0.709108, with a mean 2σ error of 0.000025. These values lie within the range of modern marine Sr isotope ratios (0.70910-0.70922), as previously defined using analyses of both seawater and marine carbonates (see compilation by Faure and Mensing, 2005). Despite their small variation, the 87Sr/86Sr ratios obtained in G. bulloides seem to indicate that Sr dissolved in seawater at the KC 024-19 core site became slightly less radiogenic after the Last Glacial Maximum (LGM). This decrease is concomitant with diminishing amounts of the detrital components in the sediments (Fig. 1). Therefore, both the composition of dissolved Sr, as revealed by results on tests of planktonic foraminifera, and the proportions of suspended terrigenous particulate material arriving at the KC 024-19 site point to a decreasing importance of the contribution of the erosion of the Iberian Variscan crust since the Last Glacial Maximum and in the Holocene. The 87Sr/86Sr ratios measured in tests of benthic foraminifera (C. wuellerstorfi) are more erratic and no correlation can be established with palaeogeographical/palaeoclimatic constraints. The difference between the behaviour of Sr compositions in G. bulloides and C. wuellerstorfi may indicate that whilst the planktonic foraminifera should reproduce very closely the seawater composition, the benthic organisms should, in addition to the major role of seawater, also be affected by some sort of interaction with the sediments. As such, planktonic foraminifera are probably more reliable indicators of seawater composition in studies involving very small periods and corresponding very slight variations of the 87Sr/86Sr ratios. Taking into account that G. bulloides is a common planktonic species (living mostly in the first 50m of the water column), whose tests seem to be in equilibrium with sea water composition, variations in its 87Sr/86Sr ratios can be related with changes in the chemical composition of the water of the Atlantic Ocean off NW Iberian Margin. The highest 87Sr/86Sr values are contemporaneous with a period of low sea level (about -140 m; Dias et al., 2000) during the LGM. According to Dias et al. (2000) at 18 ka BP the shoreline was close to the shelf break. The summital parts of the Gerês and Estrela mountains were covered by local glaciers and close to the coast freezing occurred frequently. The river catchments, which extended far to the shelf, received more rainfall due to a longer, compared to present day conditions, wet season, which promoted both physical and chemical weathering. Higher pluviosity combined with the effect of spring ice melting maintained high river discharge and consequently caused very important sediment supply to the coastal zone. The extremely narrow shelf was a very energetic environment due to sea bottom inclination and very limited long wave refraction. Therefore, at that time, a long wet season and very competent rivers should have caused important erosion of the Variscan basement in NW Iberia. Additionally, then, the shoreline was much closer to the KC 024-19 site. The combination of all these factors favoured an important deposition of terrigenous sediments and the local slight enrichment in radiogenic Sr of the seawater. With sea level rise, after the deglaciation and during the Holocene, the river estuaries became progressively far away from the shelf break. Their competence of transport also became progressively reduced and the offshore transport of detrital sediments became progressively lower. Conversely the biogenic carbonate proportion in the sediments increased, due to lower dilution by the terrigenous particles. Simultaneously, the values of 87Sr/86Sr in the seawater at the KC 024-19 site became lower, as a consequence of a complete homogenization with the ocean global composition, which was now more effective with the increasing distance towards shoreline

Equality of immanantal decomposable tensors, II

We state a necessary and sufficient condition for equality of nonzero decomposable symmetrized tensors when the symmetrizer is associated to an irreducible character of the symmetric group of degree m.info:eu-repo/semantics/publishedVersio

Constraining Elko Dark Matter at the LHC with Monophoton Events

A mass dimension one fermion, also known as Elko, constitutes a dark matter candidate which might interact with photons at the tree level in a specific fashion. In this work, we investigate the constraints imposed by unitarity and LHC data on this type of interactions using the search for new physics in monophoton events. We found that Elkos which can explain the dark matter relic abundance mainly through electromagnetic interactions are excluded at the 95\%CL by the 8 TeV LHC data for masses up to 1 TeV.Comment: 6 pages, 4 figure

Caracterização da macrofauna invertebrada do solo sob diferentes fitofisionomias do Pantanal.

bitstream/item/66197/1/31473.pdfFERTBIO

Revisiting the Ediacaran-Cambrian boundary in the Ossa-Morena Zone (SW Iberia)

Some of the best outcrops of Iberia to study the Ediacaran-Cambrian boundary are located in the Ossa- Morena Zone. In the Crato-Campo Maior region (SW Iberia, Portugal), this stratigraphic boundary is marked by an angular unconformity (Gonçalves, 1971). The Ediacaran sedimentary rocks of the Série Negra Group (maximum depositional age of c. 545 Ma; Linnemann et al., 2008) are overlain by Early Cambrian strata. A folded foliation has been recognized in the Ediacaran metagreywackes, metapelites, black metachert, marbles and metabasic rocks (Pereira & Silva, 2002). This deformation event is previous to the intrusion of c. 526-525 Ma granitic rocks (Barquete and Barreiros plutons; Pereira et al., 2011; Sánchez-García et al., 2013), and is not represented in the unconformable overlying Early Cambrian strata including sandstone (maximum depositional age of c. 532 Ma; Pereira et al., 2011). At the base of the lower Cambrian stratigraphic section there is the Freixo-Segóvia volcanosedimentary complex consisting of felsic tuff interbedded with conglo-merate and rhyolitic-dacitic lava flow (Pereira et al., 2006). The conglomerate is composed of pebbles of volcanic rock (basalt, rhyolite, dacite and mafic and felsic tuff), granitic rocks, chert, quartzite, arkosic sandstone, greywacke and shale in a tuffaceous sandy matrix. This volcano-sedimentary complex is overlain by a sequence of sandstone and shale passing vertically to limestone beds which have been attributed to the lower Cambrian (Pereira et al., 2006) (see Fig. 12). An ongoing research project intends to date the volcanic rocks of the volcano-sedimentary complex using U-Pb zircon geochronology. The absolute dates determined from these volcanic rocks will provide the time framework for the calibration of the existing stratigraphic scheme based on regional correlation

Superposition relations of microfabrics in the northern hanging-wall block

This study reports alternation of D2 extension-related and D3 contraction-related microfabrics in the northern hanging wall block of a gneiss dome-like structure recognized in the Évora Massif (Ossa-Morena Zone). In the Arraiolos – Santo Antonio de Alcorrego traverse high- to low-grade mylonites are dominant. Microfabrics related to D2 ductile deformation and M2 high-amphibolite to greenschist facies characterize an extensional shear zone with telescoping metamorphic isograds. D2 microstructures indicate shear sense with top-to-SE. Superposition of D3 contraction developed under greenschist facies (M3) producing folding of D2 microfabrics, mylonitization of granites along strike-slip shear zones and retrogression of M2 mineral assemblages