1,074 research outputs found
Fertilizer use on smallholder farms in Eastern Province, Zambia:
Fertilizers Zambia Eastern Province., Farms, Small Zambia Eastern Province.,
Detecting Features in the Dark Energy Equation of State: A Wavelet Approach
We study the utility of wavelets for detecting the redshift evolution of the
dark energy equation of state w(z) from the combination of supernovae, CMB and
BAO data. We show that local features in w, such as bumps, can be detected
efficiently using wavelets. To demonstrate, we first generate a mock supernovae
(SNe) data sample for a SNAP-like survey with a bump feature in w(z) hidden in,
then successfully discover it by performing a blind wavelet analysis. We also
apply our method to analyze the recently released "Constitution" SNe data,
combined with WMAP and BAO from SDSS, and find weak hints of dark energy
dynamics. Namely, we find that models with w(z) < -1 for 0.2 < z < 0.5, and
w(z)> -1 for 0.5 < z <1, are mildly favored at 95% confidence level. This is in
good agreement with several recent studies using other methods, such as
redshift binning with principal component analysis (PCA) (e.g. Zhao and Zhang,
arXiv:0908.1568)Comment: 8 pages, 6 figures. Minor changes from v1, matches the version
published in JCAP
Numerical modelling techniques for fretting fatigue crack initiation and propagation
status: publishe
Cosmological constraints on a decomposed Chaplygin gas
Any unified dark matter cosmology can be decomposed into dark matter
interacting with vacuum energy, without introducing any additional degrees of
freedom. We present observational constraints on an interacting vacuum plus
dark energy corresponding to a generalised Chaplygin gas cosmology. We consider
two distinct models for the interaction leading to either a barotropic equation
of state or dark matter that follows geodesics, corresponding to a rest-frame
sound speed equal to the adiabatic sound speed or zero sound speed,
respectively. For the barotropic model, the most stringent constraint on
comes from the combination of CMB+SNIa+LSS(m) gives
at the 95% confidence level, which indicates that
the barotropic model must be extremely close to the CDM cosmology. For
the case where the dark matter follows geodesics, perturbations have zero sound
speed, and CMB+SNIa+gISW then gives the much weaker constraint
at the 95% confidence level.Comment: a code bug removed, typos corrected, references added, Fig.7
changed,version published in PR
Role of terms of trade in Indian agricultural growth: a national and state level analysis
Using time series data, this paper analyses the relative contributions of terms of trade and non-price variables in explaining agricultural growth in recent decades in India. Agricultural growth is largely explained by expansion of irrigation, (which in the model is also a proxy for HYVs and other capital investments), and, until the 1970s, by increases in the net cultivated area. Agricultural output is inelastic, and is becoming increasingly more so over time. The terms of trade was not an important factor in explaining past growth. Even during the late 1960s and early 1970s when the terms of trade improved by 18 percent for agriculture, they only accounted for 15 percent of the growth in output. Increases in agricultural output are also found to worsen the terms of trade for agriculture, despite government attempts to control prices. The results highlight the importance of further investments in agricultural research, extension, irrigation and other supply-enhancing inputs if the ongoing policy reforms in India are to translate into more rapid and sustained agricultural growth.Agricultural productivity India., Terms of trade India., Investment of public funds India.,
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