Edges and Diffractive Effects in Casimir Energies

The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined on the open regions of the plates or boundaries. The Casimir energy is then given in terms of the determinant of the nonlocal differential operator which defines the lower dimensional theory. We develop perturbative methods for computing these determinants. Our results are in good agreement with known results based on Monte Carlo simulations. The method is well suited to isolating the diffractive contributions to the Casimir energy.Comment: 32 pages, LaTeX, 9 figures. v2: additional discussion of renormalization procedure, version to appear in PRD. v3: corrected a sign error in (70

Diagnosis of Local Land-Atmosphere Feedbacks in India

Following the convective triggering potential (CTP)–humidity index (HIlow) framework by Findell and Eltahir, the sensitivity of atmospheric convection to soil moisture conditions is studied for India. Using the same slab model as Findell and Eltahir, atmospheric conditions in which the land surface state affects convective precipitation are determined. For India, CTP–HIlow thresholds for land surface–atmosphere feedbacks are shown to be slightly different than for the United States. Using atmospheric sounding data from 1975 to 2009, the seasonal and spatial variations in feedback strength have been assessed. The patterns of feedback strengths thus obtained have been analyzed in relation to the monsoon timing. During the monsoon season, atmospheric conditions where soil moisture positively influences precipitation are present about 25% of the time. During onset and retreat of the monsoon, the south and east of India show more potential for feedbacks than the north. These feedbacks suggest that large-scale irrigation in the south and east may increase local precipitation. To test this, precipitation data (from 1960 to 2004) for the period about three weeks just before the monsoon onset date have been studied. A positive trend in the precipitation just before the monsoon onset is found for irrigated stations. It is shown that for irrigated stations, the trend in the precipitation just before the monsoon onset is positive for the period 1960–2004. For nonirrigated stations, there is no such upward trend in this period. The precipitation trend for irrigated areas might be due to a positive trend in the extent of irrigated areas, with land–atmosphere feedbacks inducing increased precipitation

Benefit of System Science: The Case of Global Energy and Water Security

Narrowly focused, single-disciplinary science alone cannot adequately underpin policies and solutions to resolve major sustainability challenges. One example of the system’s approaches is the IIASA’s Global Energy Assessment (GEA), multidisciplinary study, whose findings were released during Rio+20 summit in 2012, and which became a major scientific underpinning of the Sustainable Development Goal (SDG) nr. 7 –Affordable and Clean Energy, adopted by the UN General Assembly in September 2015. The GEA links energy to climate, air quality, human health and mortality, economic growth, urbanization, water, land use, and other factors. The GEA scenarios find that energy access for all (by 2050) is possible with co-benefits of limiting warming to 2°C, improving air quality and human health, and stimulating economic growth within a green, inclusive economy framework. Next to GEA, other system-analytical approaches will be presented, including water-energy-food-environment nexus and human capital-education-demography nexus

Institutional governance barriers for the development and implementation of climate adaptation strategies

Abstract In this paper we summarise the main social barriers to adaptation presented in climate literature – the inherent uncertainty of climate change, fragmentation, institutional voids, short term horizon of politicians and policies, and the motives and willingness to start adapting. We have linked these topics to theories in public administration to explore if there is interesting overlap that could be beneficial for our understanding of institutional governance barriers for developing and implementing adaptation strategies. We conclude that there are strong interdependencies between what has been signalled in adaptation literature as barriers to adaptation and what has been theorised in public administration literature. However, barriers in the development of adaptation have been hardly discussed in climate adaptation literature. Therefore we argue that in order to understand factors that stagnate the development and implementation of adaptation policy strategies, existing theories of public administration could prove very valuable. Keywords; barriers; adaptation strategies; institutions; governance

Expression of Interest ICES/KIS-3 : Thema 4: Hoogwaardig Ruimtegebruik Speerpunt 6

Hoofddoel van dit speerpunt is om zowel de Nederlandse overheid als het bedrijfsleven uit te rusten met een operationele kennisinfrastructuur die toegesneden is op de relatie tussen (antropogene en natuurlijke) klimaatverandering en meervoudig ruimtegebrui

Climate research Netherlands : research highlights

In the Netherlands the temperature has risen, on average, by 1.6°C since 1900. Regional climate scenarios for the 21st century developed by the Dutch Royal Meteorological Institute [1] show that temperature in the Netherlands will continue to rise and mild winters and hot summers will become more common. On average winters will become wetter and extreme precipitation amounts will increase. The intensity of extreme rain showers in summer will increase and the sea level will continue to rise. Changing climate will affect all segments and sectors of the society and the economy of the Netherlands, but it also brings new opportunities for major innovation

Effects of precipitation uncertainty on discharge calculations for main river basins

This study quantifies the uncertainty in discharge calculations caused by uncertainty in precipitation input for 294 river basins worldwide. Seven global gridded precipitation datasets are compared at river basin scale in terms of mean annual and seasonal precipitation. The representation of seasonality is similar in all datasets, but the uncertainty in mean annual precipitation is large, especially in mountainous, arctic, and small basins. The average precipitation uncertainty in a basin is 30%, but there are strong differences between basins. The effect of this precipitation uncertainty on mean annual and seasonal discharge was assessed using the uncalibrated dynamic global vegetation and hydrology model Lund-Potsdam-Jena managed land (LPJmL), yielding even larger uncertainties in discharge (average 90%). For 95 basins (out of 213 basins for which measurements were available) calibration of model parameters is problematic because the observed discharge falls within the uncertainty of the simulated discharge. A method is presented to account for precipitation uncertainty in discharge simulations

Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surfac

Towards the lattice study of M-theory (II)

We present new results of the quenched simulations of the reduced D=4 supersymmetric Yang - Mills quantum mechanics for larger gauge groups SU(N), 2<N<9. The model, studied at finite temperature, reveals existence of the two distinct regions which may be precursors of a black hole and the elementary D0 branes phases of M-theory conjectured in the literature. Present results for higher groups confirm the picture found already for N=2. Similar behaviour is observed in the preliminary simulations for the D=6 and D=10 models.Comment: Talk presented at XIX International Symposium on Lattice Field Theory lattice2001(surfaces