2,545 research outputs found
NON-FARM LABOR SUPPLY: THEORY AND ESTIMATION
During the last decade considerable research has been carried out on the non-farm labor supply of farm households. New insights and hypotheses on the economic behavior of households, known as "new home economics," and progress in applying more sophisticated estimation techniques have stimulated these research activities. The focus of this paper is the standard neoclassical model of labor supply and a corresponding empirical research strategy. The empirical model refers to household-level data from West Germany. As the results reveal, farm households decide on the allocation of their resources in a very rational manner. This shows their high capacity and flexibility to adjust to varying economic circumstances.Labor and Human Capital,
NONDISTORTING AGRICULTURAL INCOME SUPPORT: SOME REFLECTIONS ON THE DISCUSSION IN WEST GERMANY
Agricultural Finance,
A well-scaling natural orbital theory
We introduce an energy functional for ground-state electronic structure
calculations. Its variables are the natural spin-orbitals of singlet many-body
wave functions and their joint occupation probabilities deriving from
controlled approximations to the two-particle density matrix that yield
algebraic scaling in general, and Hartree-Fock scaling in its seniority-zero
version. Results from the latter version for small molecular systems are
compared with those of highly accurate quantum-chemical computations. The
energies lie above full configuration interaction calculations, close to doubly
occupied configuration interaction calculations. Their accuracy is considerably
greater than that obtained from current density-functional theory
approximations and from current functionals of the one-particle density matrix.Comment: http://www.pnas.org/cgi/doi/10.1073/pnas.1615729113. arXiv admin
note: text overlap with arXiv:1309.392
Atmospheric studies of habitability in the Gliese 581 system
The M-type star Gliese 581 is orbited by at least one terrestrial planet
candidate in the habitable zone, i.e. GL 581 d. Orbital simulations have shown
that additional planets inside the habitable zone of GL 581 would be
dynamically stable. Recently, two further planet candidates have been claimed,
one of them in the habitable zone.
In view of the ongoing search for planets around M stars which is expected to
result in numerous detections of potentially habitable Super-Earths, we take
the GL 581 system as an example to investigate such planets. In contrast to
previous studies of habitability in the GL 581 system, we use a consistent
atmospheric model to assess surface conditions and habitability. Furthermore,
we perform detailed atmospheric simulations for a much larger subset of
potential planetary and atmospheric scenarios than previously considered.
A 1D radiative-convective atmosphere model is used to calculate temperature
and pressure profiles of model atmospheres, which we assumed to be composed of
molecular nitrogen, water, and carbon dioxide. In these calculations, key
parameters such as surface pressure and CO2 concentration as well as orbital
distance and planetary mass are varied.
Results imply that surface temperatures above freezing could be obtained,
independent of the here considered atmospheric scenarios, at an orbital
distance of 0.117 AU. For an orbital distance of 0.146 AU, CO2 concentrations
as low as 10 times the present Earth's value are sufficient to warm the surface
above the freezing point of water. At 0.175 AU, only scenarios with CO2
concentrations of 5% and 95% were found to be habitable. Hence, an additional
Super-Earth planet in the GL 581 system in the previously determined dynamical
stability range would be considered a potentially habitable planet.Comment: 5 pages, 4 figures, accepted in Astronomy&Astrophysic
Hierarchical decomposition of domains with fractures
We consider the efficient and robust numerical solution of elliptic problems with jumping coefficients occuring on a network of fractures. These thin geometric structures are resolved by anisotropic trapezoidal elements. We present an iterative solution concept based on a hierarchical separation of the fractures and the surrounding rock matrix. Upper estimates for the convergence rates are independent of the the jump of coefficients and of the width of the fractures and depend only polynomially on the number of refinement steps. The theoretical results are illustrated by numerical experiments
A Quantum Lovasz Local Lemma
The Lovasz Local Lemma (LLL) is a powerful tool in probability theory to show
the existence of combinatorial objects meeting a prescribed collection of
"weakly dependent" criteria. We show that the LLL extends to a much more
general geometric setting, where events are replaced with subspaces and
probability is replaced with relative dimension, which allows to lower bound
the dimension of the intersection of vector spaces under certain independence
conditions. Our result immediately applies to the k-QSAT problem: For instance
we show that any collection of rank 1 projectors with the property that each
qubit appears in at most of them, has a joint satisfiable
state.
We then apply our results to the recently studied model of random k-QSAT.
Recent works have shown that the satisfiable region extends up to a density of
1 in the large k limit, where the density is the ratio of projectors to qubits.
Using a hybrid approach building on work by Laumann et al. we greatly extend
the known satisfiable region for random k-QSAT to a density of
. Since our tool allows us to show the existence of joint
satisfying states without the need to construct them, we are able to penetrate
into regions where the satisfying states are conjectured to be entangled,
avoiding the need to construct them, which has limited previous approaches to
product states.Comment: 19 page
An Exact Algorithm for TSP in Degree-3 Graphs via Circuit Procedure and Amortization on Connectivity Structure
The paper presents an O^*(1.2312^n)-time and polynomial-space algorithm for
the traveling salesman problem in an n-vertex graph with maximum degree 3. This
improves the previous time bounds of O^*(1.251^n) by Iwama and Nakashima and
O^*(1.260^n) by Eppstein. Our algorithm is a simple branch-and-search
algorithm. The only branch rule is designed on a cut-circuit structure of a
graph induced by unprocessed edges. To improve a time bound by a simple
analysis on measure and conquer, we introduce an amortization scheme over the
cut-circuit structure by defining the measure of an instance to be the sum of
not only weights of vertices but also weights of connected components of the
induced graph.Comment: 24 pages and 4 figure
Very high-energy γ-ray observations of the Crab nebula and other potential sources with the GRAAL experiment
The “γ-ray astronomy at Almeria” (GRAAL) experiment uses 63 heliostat-mirrors with a total mirror area of ≈2500 m2 from the CESA-1 field at the “Plataforma Solar de Almeria” to collect Cherenkov light from air showers. The detector is located in a central solar tower and detects photon-induced showers with an energy threshold of 250±110 GeV and an asymptotic effective detection area of about 15 000 m2. A comparison between the results of detailed Monte-Carlo simulations and data is presented.
Data sets taken in the period September 1999–September 2000 in the direction of the Crab pulsar, the active galaxy 3C 454.3, the unidentified γ-ray source 3EG J1835+59 and a “pseudosource” were analyzed for high energy γ-ray emission. Evidence for a γ-ray flux from the Crab pulsar with an integral flux of 2.2±0.4 above threshold and a significance of 4.5σ in a total measuring time of 7 h and 10 min on source was found. No evidence for emission from the other sources was found.
Some difficulties with the use of heliostat fields for γ-ray astronomy are pointed out. In particular the effect of field-of-view restricted to the central part of a detected air shower on the lateral distribution and timing properties of Cherenkov light are discussed. Upon restriction the spread of the timing front of proton-induced showers sharply decreases and the reconstructed direction becomes biased towards the pointing direction. This is shown to make efficient γ-hadron separation difficult
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