Abelian homotopy Dijkgraaf-Witten theory

We construct a version of Dijkgraaf-Witten theory based on a compact abelian Lie group within the formalism of Turaev's homotopy quantum field theory. As an application we show that the 2+1-dimensional theory based on U(1) classifies lens spaces up to homotopy type.Comment: 23 pages, 1 figur

Forage legume impact on soil fertility and N balance

Dairy production systems in Europe are to a large extent based on ley-arable rotations. In the ley phase of such rotations nitrogen accumulation occurs as a result of (1) organic carbon accumulation in soil not disturbed by tillage operations and (2) a considerable nitrogen surplus in grasslands, particularly under grazing regimes where a large part of the N in ingested grass is recycled to soil via urine and faeces. The accumulation of N and C in grasslands starts soon after establishment, the rate asymptotically declining with age and depends on practices such as fertiliser level, animal feed composition, stocking density, length of grazing and the botanical composition of the sward. In these pasture systems, key perennial legumes are white clover (Trifolium repens L.) red clover (Trifolium pratense L.) and lucerne (Medicago sativa). They are used because of their valuable contribution to production, feed quality and N inputs via biological fixation of atmospheric N2 (Ledgard et al., 2010) Grassland cultivation almost always results in a substantial residual effect and the mineralization of N often exceeds the requirement of the succeeding crop. Thus, there is a high risk of nitrate leaching following sward cultivation. Management practices to control nitrate losses include delayed ploughing until late winter or spring, the use of efficient catch crops after ploughing and a reduction in fertilizer N application to cereals after ploughing. The objective of this paper is to illustrate by examples the importance of management for N fertility building and efficient utilization in crop rotations containing forage legumes

Effect of feeding fermentable fibrerich feedstuffs on meat quality with emphasis on chemical and sensory boar taint in entire male and female pigs

Skatole, androstenone and other compounds such as indole cause boar taint in entire male pork. However, female pigs also produce skatole and indole. The purpose of this experiment was to minimise boar taint and increase overall impression of sensory quality by feeding entire male and female pigs with fibrerich feedstuffs. The pigs have been fed three organic diets for either 1 or 2 weeks prior to slaughter of which two diets contained different fermentable fibre-rich feedstuffs – 10–13.3% dried chicory roots or 25% blue lupines. These two treatments were compared with pigs fed with an organic control diet for either 1 or 2 weeks prior to slaughter. Lupines significantly reduced skatole in blood and backfat for both genders after 1 week. Moreover, lupines showed negative impact on growth rate and feed conversion whilst chicory showed no significant differences in this respect. However, the indole concentration was significantly lower in chicory than lupine fed pigs. From a sensory perspective, chicory and lupine feeding reduced boar taint since odour and flavour of manure related to skatole and urine associated to androstenone were minimised. The level of boar taint in the entire male pigs was most effectively reduced after 14 days by both fibre-rich feeds while lupine had the largest influence on ‘‘boar” taint reduction in female pigs

Increasing evidence for hemispherical power asymmetry in the five-year WMAP data

(Abridged)Motivated by the recent results of Hansen et al. (2008) concerning a noticeable hemispherical power asymmetry in the WMAP data on small angular scales, we revisit the dipole modulated signal model introduced by Gordon et al. (2005). This model assumes that the true CMB signal consists of a Gaussian isotropic random field modulated by a dipole, and is characterized by an overall modulation amplitude, A, and a preferred direction, p. Previous analyses of this model has been restricted to very low resolution due to computational cost. In this paper, we double the angular resolution, and compute the full corresponding posterior distribution for the 5-year WMAP data. The results from our analysis are the following: The best-fit modulation amplitude for l <= 64 and the ILC data with the WMAP KQ85 sky cut is A=0.072 +/- 0.022, non-zero at 3.3sigma, and the preferred direction points toward Galactic coordinates (l,b) = (224 degree, -22 degree) +/- 24 degree. The corresponding results for l <~ 40 from earlier analyses was A = 0.11 +/- 0.04 and (l,b) = (225 degree,-27 degree). The statistical significance of a non-zero amplitude thus increases from 2.8sigma to 3.3sigma when increasing l_max from 40 to 64, and all results are consistent to within 1sigma. Similarly, the Bayesian log-evidence difference with respect to the isotropic model increases from Delta ln E = 1.8 to Delta ln E = 2.6, ranking as "strong evidence" on the Jeffreys' scale. The raw best-fit log-likelihood difference increases from Delta ln L = 6.1 to Delta ln L = 7.3. Similar, and often slightly stronger, results are found for other data combinations. Thus, we find that the evidence for a dipole power distribution in the WMAP data increases with l in the 5-year WMAP data set, in agreement with the reports of Hansen et al. (2008).Comment: 6 pages, 2 figures; added references and minor comments. Accepted for publication in Ap

Co- and counter-helicity interaction between two adjacent laboratory prominences

The interaction between two side-by-side solar prominence-like plasmas has been studied using a four-electrode magnetized plasma source that can impose a wide variety of surface boundary conditions. When the source is arranged to create two prominences with the same helicity (co-helicity), it is observed that helicity transfer from one prominence to the other causes the receiving prominence to erupt sooner and faster than the transmitting prominence. When the source is arranged to create two prominences with opposite helicity (counter-helicity), it is observed that upon merging, prominences wrap around each other to form closely spaced, writhing turns of plasma. This is followed by appearance of a distinct bright region in the middle and order of magnitude higher emission of soft x rays. The four-electrode device has also been used to change the angle of the neutral line and so form more pronounced S-shapes

Evidence of vorticity and shear at large angular scales in the WMAP data: a violation of cosmological isotropy?

Motivated by the large-scale asymmetry observed in the cosmic microwave background sky, we consider a specific class of anisotropic cosmological models -- Bianchi type VII_h -- and compare them to the WMAP first-year data on large angular scales. Remarkably, we find evidence of a correlation which is ruled out as a chance alignment at the 3sigma level. The best fit Bianchi model corresponds to x=0.55, Omega_0=0.5, a rotation axis in the direction (l,b)=(222degr,-62degr), shear (sigma/H)_0=2.4e-10 and a right--handed vorticity (omega/H)_0=6.1e-10. Correcting for this component greatly reduces the significance of the large-scale power asymmetry, resolves several anomalies detected on large angular scales (ie. the low quadrupole amplitude and quadrupole/octopole planarity and alignment), and can account for a non--Gaussian "cold spot" on the sky. Despite the apparent inconsistency with the best-fit parameters required in inflationary models to account for the acoustic peaks, we consider the results sufficiently provocative to merit further consideration.Comment: 4 pages, 3 figures; emulateapj.cls; ApJL accepted version plus fixed error in vorticity calculation (sqrt(2) off in Table 1, abstract, and conclusions); basic conclusions unchange

An improved 2.5 GHz electron pump: single-electron transport through shallow-etched point contacts driven by surface acoustic waves

We present an experimental study of a 2.5 GHz electron pump based on the quantized acoustoelectric current driven by surface acoustic waves (SAWs) through a shallow-etched point contact in a GaAs/AlGaAs heterostructure. At low temperatures and with an additional counter-propagating SAW beam, up to n = 20 current plateaus at I=nef could be resolved, where n is an integer, e the electron charge, and f the SAW frequency. In the best case the accuracy of the first plateau at 0.40 nA was estimated to be dI/I = +/- 25 ppm over 0.25 mV in gate voltage, which is better than previous results.Comment: 11 pages, 4 figure

Asymmetries in the CMB anisotropy field

We report on the results from two independent but complementary statistical analyses of the WMAP first-year data, based on the power spectrum and N-point correlation functions. We focus on large and intermediate scales (larger than about 3 degrees) and compare the observed data against Monte Carlo ensembles with WMAP-like properties. In both analyses, we measure the amplitudes of the large-scale fluctuations on opposing hemispheres and study the ratio of the two amplitudes. The power-spectrum analysis shows that this ratio for WMAP, as measured along the axis of maximum asymmetry, is high at the 95%-99% level (depending on the particular multipole range included). The axis of maximum asymmetry of the WMAP data is weakly dependent on the multipole range under consideration but tends to lie close to the ecliptic axis. In the N-point correlation function analysis we focus on the northern and southern hemispheres defined in ecliptic coordinates, and we find that the ratio of the large-scale fluctuation amplitudes is high at the 98%-99% level. Furthermore, the results are stable with respect to choice of Galactic cut and also with respect to frequency band. A similar asymmetry is found in the COBE-DMR map, and the axis of maximum asymmetry is close to the one found in the WMAP data.Comment: 6 pages, 5 figures; version to appear in ApJ, textual improvements, added reference

Dissipation Layers in Rayleigh-B\'{e}nard Convection: A Unifying View

Boundary layers play an important role in controlling convective heat transfer. Their nature varies considerably between different application areas characterized by different boundary conditions, which hampers a uniform treatment. Here, we argue that, independent from boundary conditions, systematic dissipation measurements in Rayleigh-B\'enard convection capture the relevant near-wall structures. By means of direct numerical simulations with varying Prandtl numbers, we demonstrate that such dissipation layers share central characteristics with classical boundary layers, but, in contrast to the latter, can be extended naturally to arbitrary boundary conditions. We validate our approach by explaining differences in scaling behavior observed for no-slip and stress-free boundaries, thus paving the way to an extension of scaling theories developed for laboratory convection to a broad class of natural systems

Structural precursor to freezing: An integral equation study

Recent simulation studies have drawn attention to the shoulder which forms in the second peak of the radial distribution function of hard-spheres at densities close to freezing and which is associated with local crystalline ordering in the dense fluid. We address this structural precursor to freezing using an inhomogeneous integral equation theory capable of describing local packing constraints to a high level of accuracy. The addition of a short-range attractive interaction leads to a well known broadening of the fluid-solid coexistence region as a function of attraction strength. The appearence of a shoulder in our calculated radial distribution functions is found to be consistent with the broadened coexistence region for a simple model potential, thus demonstrating that the shoulder is not exclusively a high density packing effect