Acceleration of the universe, vacuum metamorphosis, and the large-time asymptotic form of the heat kernel

We investigate the possibility that the late acceleration observed in the rate of expansion of the universe is due to vacuum quantum effects arising in curved spacetime. The theoretical basis of the vacuum cold dark matter (VCDM), or vacuum metamorphosis, cosmological model of Parker and Raval is revisited and improved. We show, by means of a manifestly nonperturbative approach, how the infrared behavior of the propagator (related to the large-time asymptotic form of the heat kernel) of a free scalar field in curved spacetime causes the vacuum expectation value of its energy-momentum tensor to exhibit a resonance effect when the scalar curvature R of the spacetime reaches a particular value related to the mass of the field. we show that the back reaction caused by this resonance drives the universe through a transition to an accelerating expansion phase, very much in the same way as originally proposed by Parker and Raval. Our analysis includes higher derivatives that were neglected in the earlier analysis, and takes into account the possible runaway solutions that can follow from these higher-derivative terms. We find that the runaway solutions do not occur if the universe was described by the usual classical FRW solution prior to the growth of vacuum energy-density and negative pressure (i.e., vacuum metamorphosis) that causes the transition to an accelerating expansion of the universe in this theory.Comment: 33 pages, 3 figures. Submitted to Physical Review D15 (Dec 23, 2003). v2: 1 reference added. No other change

Transition from decelerated to accelerated cosmic expansion in braneworld universes

Braneworld theory provides a natural setting to treat, at a classical level, the cosmological effects of vacuum energy. Non-static extra dimensions can generally lead to a variable vacuum energy, which in turn may explain the present accelerated cosmic expansion. We concentrate our attention in models where the vacuum energy decreases as an inverse power law of the scale factor. These models agree with the observed accelerating universe, while fitting simultaneously the observational data for the density and deceleration parameter. The redshift at which the vacuum energy can start to dominate depends on the mass density of ordinary matter. For Omega = 0.3, the transition from decelerated to accelerated cosmic expansion occurs at z approx 0.48 +/- 0.20, which is compatible with SNe data. We set a lower bound on the deceleration parameter today, namely q > - 1 + 3 Omega/2, i.e., q > - 0.55 for Omega = 0.3. The future evolution of the universe crucially depends on the time when vacuum starts to dominate over ordinary matter. If it dominates only recently, at an epoch z < 0.64, then the universe is accelerating today and will continue that way forever. If vacuum dominates earlier, at z > 0.64, then the deceleration comes back and the universe recollapses at some point in the distant future. In the first case, quintessence and Cardassian expansion can be formally interpreted as the low energy limit of our model, although they are entirely different in philosophy. In the second case there is no correspondence between these models and ours.Comment: In V2 typos are corrected and one reference is added for section 1. To appear in General Relativity and Gravitatio

Dark energy and dark matter from an inhomogeneous dilaton

A cosmological scenario is proposed where the dark matter (DM) and dark energy (DE) of the universe are two simultaneous manifestations of an inhomogenous dilaton. The equation of state of the field is scale-dependent and pressureless at galactic and larger scales and it has negative pressure as a DE at very large scales. The dilaton drives an inflationary phase followed by a kinetic energy-dominated one, as in the "quintessential inflation" model introduced by Peebles & Vilenkin, and soon after the end of inflation particle production seeds the first inhomogeneities that lead to galaxy formation. The dilaton is trapped near the minimum of the potential where it oscillates like a massive field, and the excess of kinetic energy is dissipated via the mechanism of "gravitational cooling" first introduced by Seidel & Suen. The inhomogeneities therefore behave like solitonic oscillations around the minimum of the potential, known as "oscillatons", that we propose account for most DM in galaxies. Those regions where the dilaton does not transform enough kinetic energy into reheating or carry an excess of it from regions that have cooled, evolve to the tail of the potential as DE, driving the acceleration of the universe.Comment: 9 pages, 8 figures, uses revtex, submitted PR

Emotional intelligence and British expatriates’ cross-cultural adjustment in international construction projects

© 2016 Informa UK Limited, trading as Taylor & Francis Group. Today’s internationalized business demands global mindset, intercultural sensitivity and the ability to skilfully negotiate through cross-cultural interactions. Therefore, the overall aim was to investigate the influence of emotional intelligence (EI) on cross-cultural adjustment (CCA) of British expatriates working on International Architectural, Engineering and Construction assignments in Sub-Saharan Africa, China, Middle East and Indian Sub-Continent. Specifically, the causal relationship between EI and three facets of CCA i.e. work, general and interaction adjustment was explored. A sequential exploratory mixed methods design was adopted. These include extensive review of existing literature, eighteen unstructured interviews, and questionnaire survey of 191 British expatriates operating in 29 different countries from the four regions under investigation. Structural equation modelling was used to assess the causal relationship between EI and CCA. Results show that EI accounted for 91, 64 and 24% of the variance in work, interaction and general adjustment respectively. Overall, the model was able to explain 60% variance in CCA, suggesting that EI competencies play a huge role in facilitating an expatriate understand and adapt to host country culture. The findings would help decision-makers (HR managers) during expatriate selection process, in understanding that along with technical skills, it is the emotional competencies that are crucial in assisting expatriates adjust to foreign way of life

An exact model of conformal quintessence

A non--minimally coupled quintessence model is investigated and the conditions for a stationary solution to the coincidence problem are obtained. For a conformally coupled scalar field and dissipative matter, a general solution possessing late acceleration is found. It fits rather well the high redshift supernovae data and gives a good prediction of the age of the Universe. Likewise, the cold dark matter component dominates the cosmological perturbations at late times albeit they decrease with expansion.Comment: 19 pages, RevTeX 4, 4 figures, to appear in Phys. Rev.

The SPTPoL extended cluster survey

We describe the observations and resultant galaxy cluster catalog from the 2770 deg2 SPTpol Extended Cluster Survey (SPT-ECS). Clusters are identified via the Sunyaev-Zel'dovich (SZ) effect and confirmed with a combination of archival and targeted follow-up data, making particular use of data from the Dark Energy Survey (DES). With incomplete follow-up we have confirmed as clusters 244 of 266 candidates at a detection significance ξ ≥ 5 and an additional 204 systems at 4 4 threshold, and 10% of their measured SZ flux. We associate SZ-selected clusters, from both SPT-ECS and the SPT-SZ survey, with clusters from the DES redMaPPer sample, and we find an offset distribution between the SZ center and central galaxy in general agreement with previous work, though with a larger fraction of clusters with significant offsets. Adopting a fixed Planck-like cosmology, we measure the optical richness-SZ mass (l - M) relation and find it to be 28% shallower than that from a weak-lensing analysis of the DES data-a difference significant at the 4σ level-with the relations intersecting at λ = 60. The SPT-ECS cluster sample will be particularly useful for studying the evolution of massive clusters and, in combination with DES lensing observations and the SPT-SZ cluster sample, will be an important component of future cosmological analyses

Detection of CMB-cluster lensing using polarization data from SPTpol

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes Q U map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500     deg 2 survey at the locations of roughly 18 000 clusters with richness λ ≥ 10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8 σ . The mean stacked mass of the selected sample is found to be ( 1.43 ± 0.40 ) × 10 14 M ⊙ which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements

Ecological networks act as extensions of protected areas for arthropod biodiversity conservation

1.Landscape-scale ecological networks (ENs) are composed of linear corridors and are widely used to mitigate the adverse effects of intensive land use. One drawback with ENs used for conservation is that being small or linear they result in more edge relative to interior than would be the case naturally. Furthermore, there is little evidence to date that ENs do conserve indigenous biodiversity. 2.Here, we use five arthropod taxa at many sites over two geographical areas within South Africa with different elevations and grassland types to test the conservation value of remnant grassland ENs in a plantation forestry context. In particular, the relative value of arthropod biodiversity in exotic plantation blocks, their edges and the interiors of ENs among the plantations were compared with those in neighbouring protected areas (PAs). We use the effects that the plantation blocks have on the adjacent PAs as a reference for comparing the ENs among the plantations. Arthropods were selected to represent biodiversity, as they are small, diverse, habitat sensitive, resource dependent, ecologically important and can be sampled in large numbers. 3.In total, 10422 individuals from 244 species were sampled. Importantly, there were no significant differences in species richness, abundance or assemblage composition between EN interior zones and PA interior zones in both geographical areas. 4.Using earlier established edge zones of 32m, we found that plantation blocks had the lowest species richness and abundance compared with either grassland edge zones (64m) to overcome edge effects, they can support similar levels and quality of arthropod biodiversity as protected areas. Remnant grassland ecological networks in agroforestry can provide natural finger-like extensions from neighbouring protected areas and therefore have conservation value. © 2012 The Authors. Journal of Applied Ecology © 2012 British Ecological Society

Current control of phytosanitary insect pests in table grape vineyards of the Hex River Valley, South Africa

Phlyctinus callosus (Coleoptera: Curculionidae), a key phytosanitary pest of South African table grapes, is controlled using sticky Plantex® trunk barriers, while Epichoristodes acerbella (Lepidoptera: Tortricidae), another important phytosanitary pest, is controlled using DiPel® (Bacillus thuringiensis var. kurstaki). Other less important pests are Gonocephalum simplex (Coleoptera: Tenebrionidae), Dysdercus fasciatus (Hemiptera: Pyrrhocoridae) and Gryllus bimaculatus (Orthoptera: Gryllidae). Bunches of grapes in vineyards were sampled for all phytosanitary pests during the 2003/2004 season, by both direct inspection and by shaking individual bunches to collect insects that fell. Insects moving up the vine trunk were collected with cardboard collars. The heads and bases of vines were also inspected. Cover crops and surrounding habitats were sampled by sweep netting. Pheromone traps, using E. acerbella pheromone capsules, were placed in vineyards. Abundance of pests was related to presence or absence of sticky trunk barriers, use of DiPel® (Bacillus thuringiensis var. kurstaki), mean rainfall and maximum temperature, height and type of cover crop. The effects of surrounding habitats, time of day pests were active and the time of year they were found was also evaluated. Use of Plantex® trunk barriers gave effective preventive control of P. callosus. DiPel® was effective against E. acerbella larvae. Numbers of P. callosus weevils increased after periods of high ambient temperatures, while E. acerbella numbers decreased following rainfall. Most phytosanitary pests infested vineyards from adjacent vineyards, with few pests recorded in cover crops or in surrounding uncultivated habitats. Thus, successful long-term reduction in phytosanitary rejections of table grapes from the Hex River Valley, South Africa, requires the coordinated control of phytosanitary pests within vineyards.Articl

Importance of using many taxa and having adequate controls for monitoring impacts of fire for arthropod conservation

Fire is a key natural and anthropogenic disturbance factor across many ecosystems, and also an important conservation management tool. However, little is known about arthropod responses to fire, particularly in Mediterranean-type ecosystems, including the biodiverse Cape Floristic Region (CFR). We investigate here the relative variety of responses by different arthropod taxa to fire, and ask whether single-taxon or multi-taxa approaches better suit post-fire biomonitoring for conservation management. Sampling involved multiple techniques and was conducted before fire, 1 year after fire, and 3 years after fire, with unburned areas as controls. Before-and-after statistics were used to identify changes in arthropod populations and assemblages as a result of fire, and between treatment and control sites. However, this was against a background of the annual effects having a major influence on the arthropods, irrespective of fire. Abundance was so variable, even in control plots, that we found it an unreliable indicator of the impact of fire. Overall, arthropods were remarkably resilient to fire, with most taxa recovering in species richness and assemblage composition within 3 years of the fire. Although all taxa showed resilience to fire, there was nevertheless little congruence in temporal recovery of the various taxa. Our results highlight the shortcomings of monitoring fire impacts using only a single-taxon without prior testing for complementarity or sensitivity to fire, while emphasizing the importance of sampling a wide range of taxa to represent overall responses of compositional biodiversity. From this, we recommend, at least for the CFR, that a cross-section of taxa, such as butterflies, ants, and scarab beetles, be used for monitoring arthropods in recovery/fire management conservation programmes. We also recommend that such monitoring be considered against the background of large annual variation seen in unburned areas. © 2011 Springer Science+Business Media B.V