21,089 research outputs found
ENVIRONMENTAL AND ECONOMIC ACCOUNTING FOR THE GERMAN AGRICULTURAL SECTOR
How can we estimate the negative externalities of agriculture at the national level, and attribute these to specific production activities and outputs? The paper presents a method that calculates the mass flow in the whole agricultural sector including inputs from other sectors, and that allows to analyse resource use and emissions, e.g. of greenhouse gases. Data inputs are the German economic accounts for agriculture, farm structural survey and market statistics, as well as environmental statistics. In the framework of the German agricultural sector model RAUMIS, material flows within the agricultural sector are described, as well as inputs from other German sectors and imports. Through a processanalytical approach, all information is integrated and matrices of resource use and emissions for all agricultural production activities are generated. A monetary allocation is used to identify the respective activities that are responsible for emissions, including indirect emissions in upstream sectors. Related to the market output, cumulative emissions per unit of output can be computed. Results for the period from 1995 to 2007 show the trend of resource uses and emissions for the national average values of important commodities such as milk and meat.SEEA, Input-Output Analysis, agriculture, resource use, trade, emissions, carbon footprint, Livestock Production/Industries, Resource /Energy Economics and Policy,
Role of QCD compositeness in the production of scalar and tensor mesons through single-photon annihilation
We study the exclusive production of scalar and tensor mesons through single-photon annihilation . Using QCD compositeness of the involved hadrons considered as
quark-antiquark systems, the prediction for the scaling of the differential
cross sections of these processes is at large . We
further derive the scaling of the and transition form factors:
and . Results for the respective cross
sections of the scalar and tensor meson production are presented. Note, when
scalar and tensor mesons are considered as tetraquark systems of two tightly
bound color diquarks, corresponding to them transition form factors and
differential cross sections have the same falloffs as in case of
quark-antiquark picture. For other tetraquark or two-hadron molecules
configurations the transition form factors and
the differential cross section have additional and
falloffs, respectively.Comment: 7 page
Direct Detection of Leptophilic Dark Matter in a Model with Radiative Neutrino Masses
We consider an electro-weak scale model for Dark Matter (DM) and radiative
neutrino mass generation. Despite the leptophilic nature of DM with no direct
couplings to quarks and gluons, scattering with nuclei is induced at the 1-loop
level through photon exchange. Effectively, there are charge-charge,
dipole-charge and dipole-dipole interactions. We investigate the parameter
space consistent with constraints from neutrino masses and mixing, charged
lepton-flavour violation, perturbativity, and the thermal production of the
correct DM abundance, and calculate the expected event rate in DM direct
detection experiments. We show that current data from XENON100 start to
constrain certain regions of the allowed parameter space, whereas future data
from XENON1T has the potential to significantly probe the model.Comment: 24 pages, 8 figures, 2 tables, discussion of large theta13 added,
version to appear in PR
Resummed effective action in the world-line formalism
Using the world-line method we resum the scalar one-loop effective action.
This is based on an exact expression for the one-loop action obtained for a
background potential and a Taylor expansion of the potential up to quadratic
order in x-space. We thus reproduce results of Masso and Rota very
economically. An alternative resummation scheme is suggested using ``center of
mass'' based loops which is equivalent under the assumption of vanishing third
and higher derivatives in the Taylor expansion but leads to simplified
expressions. In an appendix some general issues concerning the relation between
world-line integrals with fixed end points versus integrals with fixed center
are clarified. We finally note that this method is also very valuable for gauge
field effective actions where it is based on the Euler--Heisenberg type
resummation.Comment: 15 page
Low-metallicity star formation: Relative impact of metals and magnetic fields
Low-metallicity star formation poses a central problem of cosmology, as it
determines the characteristic mass scale and distribution for the first and
second generations of stars forming in our Universe. Here, we present a
comprehensive investigation assessing the relative impact of metals and
magnetic fields, which may both be present during low-metallicity star
formation. We show that the presence of magnetic fields generated via the
small-scale dynamo stabilises the protostellar disc and provides some degree of
support against fragmentation. In the absence of magnetic fields, the
fragmentation timescale in our model decreases by a factor of ~10 at the
transition from Z=0 to Z>0, with subsequently only a weak dependence on
metallicity. Similarly, the accretion timescale of the cluster is set by the
large-scale dynamics rather than the local thermodynamics. In the presence of
magnetic fields, the primordial disc can become completely stable, therefore
forming only one central fragment. At Z>0, the number of fragments is somewhat
reduced in the presence of magnetic fields, though the shape of the mass
spectrum is not strongly affected in the limits of the statistical
uncertainties. The fragmentation timescale, however, increases by roughly a
factor of 3 in the presence of magnetic fields. Indeed, our results indicate
comparable fragmentation timescales in primordial runs without magnetic fields
and Z>0 runs with magnetic fields.Comment: MNRAS in pres
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