6,034 research outputs found
Connections on modules over quasi-homogeneous plane curves
Let k be an algebraically closed field of characteristic 0, and let be a quasi-homogeneous plane curve. We show that for any graded
torsion free A-module M, there exists a natural graded integrable connection,
i.e. a graded A-linear homomorphism that satisfy the derivation property and preserves the
Lie product.
In particular, a torsion free module N over the complete local ring admits a natural integrable connection if A is a simple curve singularity,
or if A is irreducible and N is a gradable module.Comment: AMS-LaTeX, 12 pages, minor changes. To appear in Comm. Algebr
The two-and three-point correlation functions of the polarized five-year WMAP sky maps
We present the two- and three-point real space correlation functions of the
five-year WMAP sky maps, and compare the observed functions to simulated LCDM
concordance model ensembles. In agreement with previously published results, we
find that the temperature correlation functions are consistent with
expectations. However, the pure polarization correlation functions are
acceptable only for the 33GHz band map; the 41, 61, and 94 GHz band correlation
functions all exhibit significant large-scale excess structures. Further, these
excess structures very closely match the correlation functions of the two
(synchrotron and dust) foreground templates used to correct the WMAP data for
galactic contamination, with a cross-correlation statistically significant at
the 2sigma-3sigma confidence level. The correlation is slightly stronger with
respect to the thermal dust template than with the synchrotron template.Comment: 10 pages, 5 figures, published in ApJ. v2: New title, minor changes
to appendix, and fixed some typos. v3: Matches version published in Ap
The fields of uniformly accelerated charges in de Sitter spacetime
The scalar and electromagnetic fields of charges uniformly accelerated in de
Sitter spacetime are constructed. They represent the generalization of the Born
solutions describing fields of two particles with hyperbolic motion in flat
spacetime. In the limit Lambda -> 0, the Born solutions are retrieved. Since in
the de Sitter universe the infinities I^+- are spacelike, the radiative
properties of the fields depend on the way in which a given point of I^+- is
approached. The fields must involve both retarded and advanced effects: Purely
retarded fields do not satisfy the constraints at the past infinity I^-.Comment: 5 pages, 3 figures, RevTeX; Slightly expanded version of the paper
published in Physical Review Letters. (The published version can be generated
from the same TeX source.); problem with the postscript fixe
CMB likelihood approximation by a Gaussianized Blackwell-Rao estimator
We introduce a new CMB temperature likelihood approximation called the
Gaussianized Blackwell-Rao (GBR) estimator. This estimator is derived by
transforming the observed marginal power spectrum distributions obtained by the
CMB Gibbs sampler into standard univariate Gaussians, and then approximate
their joint transformed distribution by a multivariate Gaussian. The method is
exact for full-sky coverage and uniform noise, and an excellent approximation
for sky cuts and scanning patterns relevant for modern satellite experiments
such as WMAP and Planck. A single evaluation of this estimator between l=2 and
200 takes ~0.2 CPU milliseconds, while for comparison, a single pixel space
likelihood evaluation between l=2 and 30 for a map with ~2500 pixels requires
~20 seconds. We apply this tool to the 5-year WMAP temperature data, and
re-estimate the angular temperature power spectrum, , and likelihood,
L(C_l), for l<=200, and derive new cosmological parameters for the standard
six-parameter LambdaCDM model. Our spectrum is in excellent agreement with the
official WMAP spectrum, but we find slight differences in the derived
cosmological parameters. Most importantly, the spectral index of scalar
perturbations is n_s=0.973 +/- 0.014, 1.9 sigma away from unity and 0.6 sigma
higher than the official WMAP result, n_s = 0.965 +/- 0.014. This suggests that
an exact likelihood treatment is required to higher l's than previously
believed, reinforcing and extending our conclusions from the 3-year WMAP
analysis. In that case, we found that the sub-optimal likelihood approximation
adopted between l=12 and 30 by the WMAP team biased n_s low by 0.4 sigma, while
here we find that the same approximation between l=30 and 200 introduces a bias
of 0.6 sigma in n_s.Comment: 10 pages, 7 figures, submitted to Ap
Keynesian economics and the Oslo School
The economic crisis of the 1930’s hit Norway when Ragnar Frisch returned from the US to accept a professorship at University of Oslo. On his return he wrote newspaper articles proposing tax relief and monetary policies to fight the economic crisis. Frisch abandoned his monetary policies and developed his Oslo School emphasising mathematical models, econometrics, national accounts, and detailed state governance. For the next four decades this School dominated economic policy in Norway where market forces had been substituted with administrative decision making. Keynes, with his General Theory, pointed out that a market economy with an active government can secure full employment. When the ideas of the Oslo School were challenged at the end of the 1970’s, by academics and through the poor performance of the economy, it collapsed. A decentralised market economy was reintroduced and The Keynesian paradigm emerged as the preferred theory compared to the approach of the Oslo School.
Full or partial outdoor rearing of slaughter pigs – effects on performance, carcass quality and nutrient load
An experiment with slaughter pigs from weaning to slaughter including five treatments and five replicates was carried out at the Danish organic experimental station, Rugballegård. Treatments included full or partial outdoor rearing of the pigs, and the replicates covered the seasonal effects. Pigs fed ad libitum indoors had a significantly lower feed consumption (5 MJ ME /kg gain), a lower lean percentage (2.3% points), and a higher backfat depth (1.1 mm, P < 0.05) than pigs fed ad libitum outdoors. Compared with outdoor pigs fed ad libitum, restricted feeding outdoors resulted in a significantly lower daily gain (107 g), a lower feed consumption (6.3 MJ ME/kg gain), higher lean percentage (2.1% points), and a reduced backfat (1.8 mm) (P <0.001). The content of soil nitrogen was considerably higher than for the soil outside the paddocks. Despite a considerable variation within the paddocks, N was distributed throughout the paddock. The present investigation highlights the fact that outdoor rearing of organic finishers may be a competitive option even in a temperate climate and all year round
In field N transfer, build-up, and leaching in ryegrass-clover mixtures
Two field experiments investigating dynamics in grass-clover mixtures were conducted, using 15N- and 14C-labelling to trace carbon (C) and nitrogen (N) from grass (Lolium perenne L.) and clover (Trifolium repens L. and Trifolium pratense L.). The leaching of dissolved inorganic nitrogen (DIN), as measured in pore water sampled by suction cups, increased during the autumn and winter, whereas the leaching of dissolved organic nitrogen (DON) was fairly constant during this period. Leaching of 15N from the sward indicated that ryegrass was the direct source of less than 1-2 percent of the total N leaching measured, whereas N dynamics pointed to clover as an important contributor to N leaching. Sampling of roots indicates that the dynamics in smaller roots were responsible for N and C build-up in the sward, and that N became available for transfer among species and leaching from the root zone. The bi-directional transfer of N between ryegrass and clover could however not be explained only by root turnover. Other processes like direct uptake of organic N compounds, may have contributed
Tournaments with prize-setting agents
In many tournaments it is the contestants themselves who determine reward allocation. Labor-union members bargain over wage distribution, and many firms allow self-managed teams to freely determine internal resource allocation, incentive structure, and division of labour. We analyze, and test experimentally, a rank-order tournament where heterogenous agents determine the spread between winner prize and looser prize. We investigate the relationship between prize spread, uncertainty (i.e. noise between e¤ort and performance), heterogeneity and effort. The paper challenges well-known results from tournament theory. We find that a large prize spread is associated with low degree of uncertainty and high degree of heterogeneity, and that heterogeneity triggers effort. By and large, our real-effort experiment supports the theoretical predictions.Rank-order tournament; prize spread; ability-difference
The Rise and Fall of the Oslo School
In 1931 Ragnar Frisch became professor at the University of Oslo. By way of his research, a new study programme and new staff he created the ”Oslo School”, characterised by mathematical modelling, econometrics, economic planning and scepticism towards the market economy. Consequently, detailed state economic planning and governance dominated Norwegian economic policy for three decades after WWII. In the 1970s the School’s dominance came to an end when the belief in competitive markets gained a foothold and the economy had poor performance. As a result a decentralized market economy was reintroduced. However, mathematical modelling and econometrics remain in the core of most economic programmes.
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