1,602 research outputs found
Motivation for Technology Adoption and Its Impact on Abandonment: A Case Study of U.S. Cotton Farmers
We estimate a bivariate probit model with sample selection to identify factors affecting adoption and abandonment of precision farming technologies for cotton farmers, using the 2009 Southern Cotton Precision Farming Survey conducted in 12 Southern states in the United States. Farmers for whom being at the forefront of agricultural technology is not an important reason for adoption are more likely to abandon precision farming technologies. This study identified various factors associated with adoption and retention of precision farming technologies. Findings from this study offer significant information to policy‐makers for a better formulation of agri‐environmental programs that encourage farmers to adopt environmentally benign farming practices including precision farming technologies.Technology Abandonment, Technology Adoption, Bivariate Probit with Sample Selection, Multinomial Logit, Precision Farming, Agribusiness, Crop Production/Industries, Farm Management, Production Economics, Research and Development/Tech Change/Emerging Technologies, Q10, Q12, Q16,
The corrections to the first moment of the polarized virtual photon structure function
We present the next-to-next-to-leading order () corrections
to the first moment of the polarized virtual photon structure function
in the kinematical region ,
where is the mass squared of the probe (target) photon and
is the QCD scale parameter. In order to evaluate the three-loop-level
photon matrix element of the flavor singlet axial current, we resort to the
Adler-Bardeen theorem for the axial anomaly and we calculate in effect the
two-loop diagrams for the photon matrix element of the gluon operator. The
corrections are found to be about 3% of the sum of the
leading order () andthe next-to-leading order ()
contributions, when and , and the
number of active quark flavors is three to five.Comment: 21 page
Virtual photon structure functions and positivity constraints
We study the three positivity constraints among the eight virtual photon
structure functions, derived from the Cauchy-Schwarz inequality and which are
hence model-independent. The photon structure functions obtained from the
simple parton model show quite different behaviors in a massive quark or a
massless quark case, but they satisfy, in both cases, the three positivity
constraints. We then discuss an inequality which holds among the unpolarized
and polarized photon structure functions , and
, in the kinematic region , where is the mass squared of the probe (target) photon, and we examine
whether this inequality is satisfied by the perturbative QCD results.Comment: 24 pages, 13 eps figure
Has the QCD RG-Improved Parton Content of Virtual Photons been Observed?
It is demonstrated that present and DIS ep data on the structure of
the virtual photon can be understood entirely in terms of the standard `naive'
quark--parton model box approach. Thus the QCD renormalization group (RG)
improved parton distributions of virtual photons, in particular their gluonic
component, have not yet been observed. The appropriate kinematical regions for
their future observation are pointed out as well as suitable measurements which
may demonstrate their relevance.Comment: 24 pages, LaTeX, 5 figure
Moments of the Virtual Photon Structure Function
The photon structure function is a useful testing ground for QCD. It is
perturbatively computable apart from a contribution from what is usually called
the hadronic component of the photon. There have been many proposals for this
nonperturbative part of the real photon structure function. By studying moments
of the virtual photon structure function, we explore the extent to which these
proposed nonperturbative contributions can be identified experimentally.Comment: LaTeX, 16 pages + 14 compressed and uuencoded postscript figures,
UMN-TH-1111/9
Adaptive Optimization of Wave Functions for Fermion Lattice Models
We present a simulation algorithm for Hamiltonian fermion lattice models. A
guiding trial wave function is adaptively optimized during Monte Carlo
evolution. We apply the method to the two dimensional Gross-Neveu model and
analyze systematc errors in the study of ground state properties. We show that
accurate measurements can be achieved by a proper extrapolation in the
algorithm free parameters.Comment: 4 pages, 6 figures (Encapsulated PostScript
Generating All Wigner Functions
In the context of phase-space quantization, matrix elements and observables
result from integration of c-number functions over phase space, with Wigner
functions serving as the quasi-probability measure. The complete sets of Wigner
functions necessary to expand all phase-space functions include off-diagonal
Wigner functions, which may appear technically involved. Nevertheless, it is
shown here that suitable generating functions of these complete sets can often
be constructed, which are relatively simple, and lead to compact evaluations of
matrix elements. New features of such generating functions are detailed and
explored for integer-indexed sets, such as for the harmonic oscillator, as well
as continuously indexed ones, such as for the linear potential and the
Liouville potential. The utility of such generating functions is illustrated in
the computation of star functions, spectra, and perturbation theory in phase
space.Comment: LaTex2e, 21 page
- …