Finite Approximations of Physical Models over Local Fields

We show that the Schr\"odinger operator associated with a physical system over a local field can be approximated in a very strong sense by finite Schr\"odinger operators. Some striking numerical results are included at the end of the article

A discussion of norms for S supply in organic farming based on content in forage and ruminant performance in Norway

The content of sulphur (S) in grassland on 27 Norwegian organic farms with dairy or sheep production was investigated in 2001 and 2002. The forage content of S was below the norms (2 g S kg DM-1) for both plants and animals in a large proportion of the samples. The average S content in forage at dairy farms was 1.4 g S kg DM-1 and at sheep farms 1.5 g. Even on grasslands with low plant S content (<1 g S kg DM-1), S-fertilization did not increase yields and increased the plants’ S content only very slightly. No indications of S deficiency were observed on the dairy farms. For one sheep farm with a forage S content of 1.1 ± 0.1g S kg DM-1, brittle and short winter wool was reported

Produksjon og utnytting av gjenvekst ved høge avdråttsnivå

Kyr med høg avdrått må få energirikt grovfôr frå eng som er tidleg og hyppig slått, og der gjenvekstar utgjer ein stor del av årsavlinga. Mellom vårvekst og gjenvekst vil det vere variasjon i proteininnhald og fiberkvalitet. Det trengst meir kunnskap om korleis ein kan balansere dei ulike kvalitetane i ei målretta fôring

Pair-copula constructions of multiple dependence

Building on the work of Bedford, Cooke and Joe, we show how multivariate data, which exhibit complex patterns of dependence in the tails, can be modelled using a cascade of pair-copulae, acting on two variables at a time. We use the pair-copula decomposition of a general multivariate distribution and propose a method to perform inference. The model construction is hierarchical in nature, the various levels corresponding to the incorporation of more variables in the conditioning sets, using pair-copulae as simple building blocs. Pair-copula decomposed models also represent a very flexible way to construct higher-dimensional coplulae. We apply the methodology to a financial data set. Our approach represents the first step towards developing of an unsupervised algorithm that explores the space of possible pair-copula models, that also can be applied to huge data sets automatically

Contribution of N from frequently chopped green manure to a succeeding crop of barley

The aim of the present work was to study to what extent N in mulched green manure herbage contributes to spring barley grain yield the subsequent year. The green manure herbage was either chopped and left on stubble (GML) or removed (GMR). On silty clay loam with spring incorporated green manure the subsequent barley grain yield was 10% higher with GML than with GMR. The additional grain N yield of 4 kg ha-1 with GML corresponded to only 3 % of N in above-ground green manure biomass. On loamy soil with late autumn incorporated green manure the treatments did not affect the grain yield the subsequent year. How large part of the N that was lost through leaching or gaseous emissions and how large part that was built into soil organic matter was not measured. However, this investigation confirms that potential N losses from mowed green manure might be large. Alternative ways of using the herbage should be found

Monte Carlo simulations of dissipative quantum Ising models

The dynamical critical exponent $z$ is a fundamental quantity in characterizing quantum criticality, and it is well known that the presence of dissipation in a quantum model has significant impact on the value of $z$. Studying quantum Ising spin models using Monte Carlo methods, we estimate the dynamical critical exponent $z$ and the correlation length exponent $\nu$ for different forms of dissipation. For a two-dimensional quantum Ising model with Ohmic site dissipation, we find $z \approx 2$ as for the corresponding one-dimensional case, whereas for a one-dimensional quantum Ising model with Ohmic bond dissipation we obtain the estimate $z \approx 1$.Comment: 9 pages, 8 figures. Submitted to Physical Review