24,997 research outputs found
Mott transition in the Hubbard model away from particle-hole symmetry
We solve the Dynamical Mean Field Theory equations for the Hubbard model away
from the particle-hole symmetric case using the Density Matrix Renormalization
Group method. We focus our study on the region of strong interactions and
finite doping where two solutions coexist. We obtain precise predictions for
the boundaries of the coexistence region. In addition, we demonstrate the
capabilities of this precise method by obtaining the frequency dependent
optical conductivity spectra.Comment: 4 pages, 4 figures; updated versio
Catastrophic Drought Insurance based on the Remotely Sensed Normalized Difference Vegetation Index for Smallholder Farmers in Zimbabwe
Index insurance, which indemnifies agricultural producers based on an objectively observable variable that is highly correlated with production losses but which cannot be influenced by the producer, can provide adequate protection against catastrophic droughts without suffering from the moral hazard and adverse selection problems that typically cause conventional agricultural insurance programs to fail. Using historical maize and cotton yield data from nine districts in Zimbabwe, we find that catastrophic drought insurance contracts based on the Normalized Difference Vegetation Index (NDVI) can be constructed whose indemnities exhibit higher correlations with yield losses compared to the conventional rainfall index. In addition the NDVI contracts can be offered within the 5–10 per cent premium range considered reasonably affordable to many poor smallholder farmers in Zimbabwe.Crop Production/Industries, Risk and Uncertainty,
On Galois-Division Multiple Access Systems: Figures of Merit and Performance Evaluation
A new approach to multiple access based on finite field transforms is
investigated. These schemes, termed Galois-Division Multiple Access (GDMA),
offer compact bandwidth requirements. A new digital transform, the Finite Field
Hartley Transform (FFHT) requires to deal with fields of characteristic p, p
\neq 2. A binary-to-p-ary (p \neq 2) mapping based on the opportunistic
secondary channel is introduced. This allows the use of GDMA in conjunction
with available digital systems. The performance of GDMA is also evaluated.Comment: 6 pages, 4 figures. In: XIX Simposio Brasileiro de Telecomunicacoes,
2001, Fortaleza, CE, Brazi
Multiplicative local linear hazard estimation and best one-sided cross-validation
This paper develops detailed mathematical statistical theory of a new class of cross-validation techniques of local linear kernel hazards and their multiplicative bias corrections. The new class of cross-validation combines principles of local information and recent advances in indirect cross-validation. A few applications of cross-validating multiplicative kernel hazard estimation do exist in the literature. However, detailed mathematical statistical theory and small sample performance are introduced via this paper and further upgraded to our new class of best one-sided cross-validation. Best one-sided cross-validation turns out to have excellent performance in its practical illustrations, in its small sample performance and in its mathematical statistical theoretical performance
Harnack's Inequality for Parabolic De Giorgi Classes in Metric Spaces
In this paper we study problems related to parabolic partial differential
equations in metric measure spaces equipped with a doubling measure and
supporting a Poincare' inequality. We give a definition of parabolic De Giorgi
classes and compare this notion with that of parabolic quasiminimizers. The
main result, after proving the local boundedness, is a scale and location
invariant Harnack inequality for functions belonging to parabolic De Giorgi
classes. In particular, the results hold true for parabolic quasiminimizers
Extracting CKM phase from and ,
We discuss some aspects of the search for CP asymmetry in the three body B
decays, revealed through the interference among neighbor resonances in the
Dalitz plot. We propose a competitive method to extract the CKM angle
combining Dalitz plot amplitude analysis of
and untagged , . The method also obtains the
ratio and phase difference between the {\it tree} and {\it penguin}
contributions from and decays and the
CP asymmetry between and . From Monte Carlo studies of 100K
events for the neutral mesons, we show the possibility of measuring .Comment: Revised enlarged version to appear at Phys Rev
Valence-bond theory of highly disordered quantum antiferromagnets
We present a large-N variational approach to describe the magnetism of
insulating doped semiconductors based on a disorder-generalization of the
resonating-valence-bond theory for quantum antiferromagnets. This method
captures all the qualitative and even quantitative predictions of the
strong-disorder renormalization group approach over the entire experimentally
relevant temperature range. Finally, by mapping the problem on a hard-sphere
fluid, we could provide an essentially exact analytic solution without any
adjustable parameters.Comment: 5 pages, 3 eps figure
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