Spherically Symmetric and Rotating Wormholes Produced by Lightlike Branes

Lightlike p-branes (LL-branes) with dynamical (variable) tension allow simple and elegant Polyakov-type and dual to it Nambu-Goto-like world-volume action formulations. Here we first briefly describe the dynamics of LL-branes as test objects in various physically interesting gravitational backgrounds of black hole type, including rotating ones. Next we show that LL-branes are the appropriate gravitational sources that provide proper matter energy momentum tensors in the Einstein equations of motion needed to generate traversable wormhole solutions, in particular, self-consistent cylindrical rotating wormholes, with the LL-branes occupying their throats. Here a major role is being played by the dynamical LL-brane tension which turns out to be negative but may be of arbitrary small magnitude. As a particular solution we obtain traversable wormhole with Schwarzschild geometry generated by a LL-brane positioned at the wormhole throat, which represents the correct consistent realization of the original Einstein-Rosen "bridge" manifold.Comment: 27 pages; important clarifications regarding the meaning of the original Einstein-Rosen "bridge" construction; an important addition to the Appendix; acknowledgments adde

Hiding and Confining Charges via "Tube-like" Wormholes

We describe two interesting effects in wormhole physics. First, we find that a genuinely charged matter source may appear neutral to an external observer - a phenomenon opposite to the famous Misner-Wheeler "charge without charge" effect. This phenomenon takes place when coupling a bulk gravity/nonlinear-gauge-field system to a charged lightlike brane as a matter source. The "charge-hiding" effect occurs in a wormhole solution which connects a non-compact "universe", comprising the exterior region of Schwarzschild-(anti-)de-Sitter (SdS) or purely Schwarzschild black hole beyond the Schwarzschild horizon, to a Levi-Civita-Bertotti-Robinson-type (LCBR) "tube-like" "universe" via a wormhole "throat" occupied by the brane. In this solution the whole electric flux produced by the brane is expelled into the "tube-like" "universe" and the brane is detected as neutral by an observer in the non-compact "universe". Next, we find a truly charge-confining wormhole solution when we couple the bulk gravity/nonlinear-gauge-field system to two oppositely charged lightlike branes. The latter system possesses a "two-throat" wormhole solution, where the "left-most" and the "right-most" "universes" are two identical copies of the exterior region of SdS black hole beyond the Schwarzschild horizon, whereas the "middle" "universe" is of LCBR "tube-like" form with geometry dS_2 x S^2. It comprises the finite-extent intermediate region of dS_2 between its two horizons. Both "throats" are occupied by the two oppositely charged lightlike branes and the whole electric flux produced by the latter is confined entirely within the middle "tube-like" "universe". A crucial ingredient is the special form of the nonlinear gauge field action, which contains both the standard Maxwell term as well as a square root of the latter. This theory was previously shown to produce a QCD-like confining dynamics in flat space-time.Comment: 26 pages, 2 figures; v.2 several references added, missing constant factors in few equations inserted, acknowledgement added, results unchanged; v.3 28 pages, several clarifying remarks, references and acknowledgements added, version to appear in International Journal of Modern Physics

A foundation for provitamin A biofortification of maize: genome-wide association and genomic prediction models of carotenoid levels.

Efforts are underway for development of crops with improved levels of provitamin A carotenoids to help combat dietary vitamin A deficiency. As a global staple crop with considerable variation in kernel carotenoid composition, maize (Zea mays L.) could have a widespread impact. We performed a genome-wide association study (GWAS) of quantified seed carotenoids across a panel of maize inbreds ranging from light yellow to dark orange in grain color to identify some of the key genes controlling maize grain carotenoid composition. Significant associations at the genome-wide level were detected within the coding regions of zep1 and lut1, carotenoid biosynthetic genes not previously shown to impact grain carotenoid composition in association studies, as well as within previously associated lcyE and crtRB1 genes. We leveraged existing biochemical and genomic information to identify 58 a priori candidate genes relevant to the biosynthesis and retention of carotenoids in maize to test in a pathway-level analysis. This revealed dxs2 and lut5, genes not previously associated with kernel carotenoids. In genomic prediction models, use of markers that targeted a small set of quantitative trait loci associated with carotenoid levels in prior linkage studies were as effective as genome-wide markers for predicting carotenoid traits. Based on GWAS, pathway-level analysis, and genomic prediction studies, we outline a flexible strategy involving use of a small number of genes that can be selected for rapid conversion of elite white grain germplasm, with minimal amounts of carotenoids, to orange grain versions containing high levels of provitamin A

Lightlike Brane as a Gravitational Source of Misner-Wheeler-Type Wormhole

Consistent Lagrangian description of lightlike p-branes (LL-branes) is presented in two equivalent forms - a Polyakov-type formulation and a dual to it Nambu-Goto-type formulation. An important characteristic feature of the LL-branes is that the brane tension appears as a non-trivial additional dynamical degree of freedom. Next, properties of p=2 LL-brane dynamics (as a test brane) in D=4 Kerr or Kerr-Newman gravitational backgrounds are discussed in some detail. It is shown that the LL-brane automatically positions itself on the horizon and rotates along with the same angular velocity. Finally, a Misner-Wheeler-type of Reissner-Nordstroem wormhole is constructed in a self-consistent electrically sourceless Einstein-Maxwell system in the D=4 bulk interacting with a LL-brane. The pertinent wormhole throat is located precisely at the LL-brane sitting on the outer Reissner-Nordstroem horizon with the Reissner-Nordstroem mass and charge being functions of the dynamical LL-brane tension.Comment: improved derivation in section 4; additional comment in conclusions; results unchange

Influencia del rendimiento sobre el estilo decisional en jugadores de fútbol

El objetivo principal del presente trabajo fue analizar cómo el nivel de rendimiento afecta al perfil de estilo decisional. Se empleó una muestra de 247 jugadores de fútbol, de los cuales 106 pertenecían a la categoría infantil y 141 a la categoría cadete. La variable independiente fue el nivel de rendimiento, determinado por el puesto que ocupó cada equipo en la clasificación final de la competición. Las variables dependientes fueron la Competencia Decisional Percibida, la Ansiedad y Agobio al Decidir y el Compromiso en el Aprendizaje Decisional, variables que fueron medidas a partir del Cuestionario de Estilo de Toma de Decisiones (CETD) (Ruiz & Graupera, 2005). Los datos determinaron diferencias significativas, en función del nivel de rendimiento, en la variable Competencia Decisional Percibida, coincidiendo este resultado con estudios anteriores (Gaspar, 2001; García, Ruiz, & Graupera, 2009). Respecto a la Ansiedad y Agobio al Decidir, los deportistas mostraron más ansiedad a medida que se incrementaba el nivel de rendimiento, siendo este resultado opuesto al que se refleja en investigaciones precedentes (López, 2002; Jiménez, 2007). Por último, en el Compromiso en el Aprendizaje Decisional no se observaron diferencias en función del nivel de rendimiento, contradiciendo igualmente a estudios anteriores que reforzaban un aumento del compromiso en función del nivel de rendimiento (Ruiz et al., 2002; Jiménez, 2004)

The (un)resolved X-ray background in the Lockman Hole

Most of the soft and a growing fraction of the harder X-ray background has been resolved into emission from point sources, yet the resolved fraction above 7 keV has only been poorly constrained. We use ~700 ks of XMM-Newton observations of the Lockman Hole and a photometric approach to estimate the total flux attributable to resolved sources in a number of different energy bands. We find the resolved fraction of the X-ray background to be ~90 per cent below 2 keV but it decreases rapidly at higher energies with the resolved fraction above ~7 keV being only ~50 per cent. The integrated X-ray spectrum from detected sources has a slope of Gamma~1.75, much softer than the Gamma=1.4 of the total background spectrum. The unresolved background component has the spectral signature of highly obscured AGN.Comment: 6 pages, 6 figures, MNRAS Letters, in press, changed to reflect accepted versio

Averaging the AGN X-ray spectra from deep Chandra fields

The X-ray spectra of Active Galactic Nuclei (AGN) carry the signatures of the emission from the central region, close to the Super Massive Black Hole (SMBH). For this reason, the study of deep X-ray spectra is a powerful instrument to investigate the origin of their emission. The emission line most often observed in the X-ray spectra of AGN is Fe K. It is known that it can be broadened and deformed by relativistic effects if emitted close enough to the central SMBH. In recent statistical studies of the X-ray spectra of AGN samples, it is found that a narrow Fe line is ubiquitous, while whether the broad features are as common is still uncertain. We present here the results of an investigation on the characteristics of the Fe line in the average X-ray spectra of AGN in deep Chandra fields. The average spectrum of the AGN is computed using Chandra spectra with more than 200 net counts from the AEGIS, Chandra Deep Field North and Chandra Deep Field South surveys. The sample spans a broader range of X-ray luminosities than other samples studied with stacking methods up to z=3.5. We analyze the average spectra of this sample using our own averaging method, checking the results against extensive simulations. Subsamples defined in terms of column density of the local absorber, luminosity and z are also investigated. We found a very significant Fe line with a narrow profile in all our samples and in almost all the subsamples that we constructed. The equivalent width (EW) of the narrow line estimated in the average spectrum of the full sample is 74 eV. The broad line component is significantly detected in the subsample of AGN with L<1.43 1E44 cgs and z<0.76, with EW=108 eV. We concluded that the narrow Fe line is an ubiquitous feature of the X-ray spectra of the AGN up to z=3.5.The broad line component is significant in the X-ray spectra of the AGN with low luminosity and low z.Comment: 17 pages, 23 figures, accepted for publication in Astronomy & Astrophysics. Replacements in the bibliography: Iwasawa K., Mainieri V., Brusa M., et al., 2011, arXiv:1111.2447v1 (previously: Iwasawa et al 2011, in preparation); Mateos S., Carrera F.J., Page M.J., et al., 2010, \aap, 510, A35 (previously: Mateos S., Warwick R.S., Carrera F.J., et al., 2008, \aap, 492, 51

High precision X-ray logN-logS distributions: implications for the obscured AGN population

We have constrained the extragalactic source count distributions over a broad range of X-ray fluxes and in various energy bands to test whether the predictions from X-ray background synthesis models agree with the observational constraints provided by our measurements. We have used 1129 XMM-Newton observations at |b|>20 deg covering a sky area of 132.3 deg^2 to compile the largest complete samples of X-ray objects to date in the 0.5-1 keV, 1-2 keV, 2-4.5 keV, 4.5-10 keV, 0.5-2 keV and 2-10 keV energy bands. Our survey includes in excess of 30,000 sources down to ~10^-15 erg/cm^2/s below 2 keV and down to ~10^{-14} erg/cm^2/s above 2 keV. A break in the source count distributions was detected in all energy bands except the 4.5-10 keV band. An analytical model comprising 2 power-law components cannot adequately describe the curvature seen in the source count distributions. The shape of the logN(>S)-logS is strongly dependent on the energy band with a general steepening apparent as we move to higher energies. This is due to non-AGN populations, comprised mainly of stars and clusters of galaxies, contribute up to 30% of the source population at energies 10^{-13} erg/cm^2/s, and these populations of objects have significantly flatter source count distributions than AGN. We find a substantial increase in the relative fraction of hard X-ray sources at higher energies, from >55% below 2 keV to >77% above 2 keV. However the majority of sources detected above 4.5 keV still have significant flux below 2 keV. Comparison with predictions from the synthesis models suggest that the models might be overpredicting the number of faint absorbed AGN, which would call for fine adjustment of some model parameters such as the obscured to unobscured AGN ratio and/or the distribution of column densities at intermediate obscuration.Comment: Accepted for publication in Astronomy and Astrophysics. Abridged Abstract. 23 pages, 47 figures, 8 table

Constraints on the distribution of absorption in the X-ray selected AGN population found in the 13H XMM-Newton/Chandra deep field

We present an analysis of the X-ray properties of sources detected in the 13H XMM-Newton deep (200ks) field. In order to constrain the absorbed AGN population, we use extensive Monte Carlo simulations to directly compare the X-ray colours of observed sources with those predicted by several model distributions. We have tested the simplest form of the AGN unified scheme, whereby the intrinsic XLF of absorbed AGN is set to be the same as that of their unabsorbed brethren, coupled with various model distributions of absorption. The best fitting of these models sets the fraction of AGN with absorbing column NH, proportional to (logNH)^8. We have also tested two extensions to the unified scheme: an evolving absorption scenario, and a luminosity dependent model distribution. Both of these provide poorer matches to the observed X-ray colour distributions than the best fitting simple unified model. We find that a luminosity dependent density evolution XLF reproduces poorly the 0.5-2 keV source counts seen in the 13H field. Field to field variations could be the cause of this disparity. Computing the simulated X-ray colours with a simple absorbed power-law + reflection spectral model is found to over-predict, by a factor of two, the fraction of hard sources that are completely absorbed below 0.5 keV, implying that an additional source of soft-band flux must be present for a number of the absorbed sources. Finally, we show that around 40% of the 13H sample are expected to be AGN with NH>10^22 cm^-2.Comment: 13 pages, 9 figures, Accepted for publication in MNRA

XMM-Newton 13H Deep field - I. X-ray sources

We present the results of a deep X-ray survey conducted with XMM-Newton, centred on the UK ROSAT 13H deep field area. This region covers 0.18 deg^2 and is the first of two areas covered with XMM-Newton as part of an extensive multi-wavelength survey designed to study the nature and evolution of the faint X-ray source population. We have produced detailed Monte-Carlo simulations to obtain a quantitative characterisation of the source detection procedure and to assess the reliability of the resultant sourcelist. We use the simulations to establish a likelihood threshold above which we expect less than 7 (3%) of our sources to be spurious. We present the final catalogue of 225 sources. Within the central 9 arcmin, 68 per cent of source positions are accurate to 2 arcsec, making optical follow-up relatively straightforward. We construct the N(>S) relation in four energy bands: 0.2-0.5 keV, 0.5-2 keV, 2-5 keV and 5-10 keV. In all but our highest energy band we find that the source counts can be represented by a double powerlaw with a bright end slope consistent with the Euclidean case and a break around 10^-14 cgs. Below this flux the counts exhibit a flattening. Our source counts reach densities of 700, 1300, 900 and 300 deg^-2 at fluxes of 4.1x10^-16, 4.5x10^-16, 1.1x10^-15 and 5.3x10^-15 cgs in the 0.2-0.5, 0.5-2, 2-5 and 5-10 keV energy bands respectively. We have compared our source counts with those in the two Chandra deep fields and Lockman hole and find our source counts to be amongst the highest of these fields in all energy bands. We resolve >51% (>50%) of the X-ray background emission in the 1-2 keV (2-5 keV) energy bands.Comment: 27 pages, 18 figures, MNRAS accepte