7,201 research outputs found
Universal Unitarity Triangle and Physics Beyond the Standard Model
We make the simple observation that there exists a universal unitarity
triangle for all models, like the SM, the Two Higgs Doublet Models I and II and
the MSSM with minimal flavour violation, that do not have any new operators
beyond those present in the SM and in which all flavour changing transitions
are governed by the CKM matrix with no new phases beyond the CKM phase. This
universal triangle can be determined in the near future from the ratio (Delta
M)_d/(Delta M)_s and sin(2 beta) measured first through the CP asymmetry in
B_d^0 to psi K_S and later in K to pi nu nubar decays. Also suitable ratios of
the branching ratios for B to X_{d,s} nu nubar and B_{d,s} to mu^+ mu^- and the
angle gamma measured by means of CP asymmetries in B decays can be used for
this determination. Comparison of this universal triangle with the
non-universal triangles extracted in each model using epsilon, (Delta M)_d and
various branching ratios for rare decays will allow to find out in a
transparent manner which of these models, if any, is singled out by experiment.
A virtue of the universal triangle is that it allows to separate the
determination of the CKM parameters from the determination of new parameters
present in the extensions of the SM considered here.Comment: 12 pages, 1 figur
Do methanethiol adsorbates on the Au(111) surface dissociate?
The interaction of methanethiol molecules CHSH with the Au(111) surface
is investigated, and it is found for the first time that the S-H bond remains
intact when the methanethiol molecules are adsorbed on the regular Au(111)
surface. However, it breaks if defects are present in the Au(111) surface. At
low coverage, the fcc region is favored for S atom adsorption, but at saturated
coverage the adsorption energies at various sites are almost iso-energetic. The
presented calculations show that a methanethiol layer on the regular Au(111)
surface does not dimerize.Comment: 4 pages, 2 figures, 4 tables, submitted to Phys. Rev. Let
For banks, fair value adjustments do infl uence dividend policy
Most researchers who investigate the interplay between fair value accounting (FVA) and the fi nancial crisis look at the time period during the crisis. This paper investigates a potential role for FVA prior to the crisis: If FVA led to increased accounting profi ts with the recognition of transitory gains through profi t and loss during the boom, and if those increased profi ts provided the rationale for increased dividends, then bank capital became riskier prior to the crisis, and this would have made the system more prone to failure. A study by Goncharov and Van Triest (2011) found no empirical support for an increase in dividends in response to unrealised positive fair value adjustments to income. In contrast, when the setting is limited to only South African banks, this paper fi nds that South African banks did pay dividends from unrealised transitory gains. This fi nding is based on a combination of three strands of evidence: a panel regression of the annual dividends declared by the large South African universal banks that showed that those banks probably ignored the unrealised nature of FVA profi ts when dividends were determined; monthly data from the total South African bank system in a co-integrated regression that showed that unrealised fair value profi ts from the banking book raised the average level of bank profi ts materially; and simple descriptive statistics on distributions that showed that South African banks distributed a greater proportion of profi ts during the critical period of 2004 to 2008 when unrealised fair value profi ts from the banking book raised the level of bank profi ts. The fi nding that South African banks did pay dividends from unrealised transitory gains was also confirmed by bank representatives and the post-fi nancial crisis disclosure of one of the South African banks.Key words: fair value accounting, dividend policy, earnings persistence, bank
The lattice of quasi-uniformities
Includes bibliographical references.Over the last thirty years much progress has been made in the investigation of the lattice of uniformities on a set X. In particular, Pelant, Reiterman, Rodl and Simon have published several articles concerning anti-atoms and complements in this lattice. The aim of this dissertation is to begin a similar investigation into the lattice of quasi-uniformities θ(X) on a set X. It starts off with a summary of results obtained for the lattice of topologies on X, which, having been studied in great detail in the past, is intended as an example as to what may be achieved with θ(X). An exposit ion of the lattice of uniformities is then given. We conclude by commencing an investigation into the lattice of quasi-uniformities on X . Where possible, results obtained for the lattice of uniformities are generalized to θ(X), and some original results for θ(X) are also presented
2-Dust : a Dust Radiative Transfer Code for an Axisymmetric System
We have developed a general purpose dust radiative transfer code for an
axisymmetric system, 2-Dust, motivated by the recent increasing availability of
high-resolution images of circumstellar dust shells at various wavelengths.
This code solves the equation of radiative transfer following the principle of
long characteristic in a 2-D polar grid while considering a 3-D radiation field
at each grid point. A solution is sought through an iterative scheme in which
self-consistency of the solution is achieved by requiring a global luminosity
constancy throughout the shell. The dust opacities are calculated through Mie
theory from the given size distribution and optical properties of the dust
grains. The main focus of the code is to obtain insights on (1) the global
energetics of dust grains in the shell (2) the 2-D projected morphologies that
are strongly dependent on the mixed effects of the axisymmetric dust
distribution and inclination angle of the shell. Here, test models are
presented with discussion of the results. The code can be supplied with a
user-defined density distribution function, and thus, is applicable to a
variety of dusty astronomical objects possessing the axisymmetric geometry.Comment: To be published in ApJ, April 2003 issue; 13 pages, 4 tables, 17
figures, 5-page appendix (no figures for the main text included in this
preprint). For the complete preprint and code distribution, contact the
author
Six Years of ScoX-1 Monitoring with BeppoSAX Wide Field Cameras
We performed a systematic analysis of 54 Wide Field Camera (WFC) observations
of ScoX-1 available in the BeppoSAX public archive. Observations span over the
six years of BeppoSAX mission lifetime and include 690 hr of data. We searched
for shifts and shape changes of the Z pattern in the color-color diagrams. We
find that the Z pattern occupies most of the time the same locus in the
color-color diagram. There are however a few exceptions, which are discussed in
detail.Comment: 4 Pages, 4 figures. To appear in Proc. of the BeppoSAX Symposium:
"The Restless High-Energy Universe", E.P.J. van den Heuvel, J.J.M. in 't
Zand, and R.A.M.J. Wijers (Eds
Drivers of land use change and household determinants of sustainability in smallholder farming systems of Eastern Uganda
Smallholder farming systems in sub-Saharan Africa have undergone changes in land use, productivity and sustainability. Understanding of the drivers that have led to changes in land use in these systems and factors that influence the systems’ sustainability is useful to guide appropriate targeting of intervention strategies for improvement. We studied low input Teso farming systems in eastern Uganda from 1960 to 2001 in a place-based analysis combined with a comparative analysis of similar low input systems in southern Mali. This study showed that policy-institutional factors next to population growth have driven land use changes in the Teso systems, and that nutrient balances of farm households are useful indicators to identify their sustainability. During the period of analysis, the fraction of land under cultivation increased from 46 to 78%, and communal grazing lands nearly completely disappeared. Cropping diversified over time; cassava overtook cotton and millet in importance, and rice emerged as an alternative cash crop. Impacts of political instability, such as the collapse of cotton marketing and land management institutions, of communal labour arrangements and aggravation of cattle rustling were linked to the changes. Crop productivity in the farming systems is poor and nutrient balances differed between farm types. Balances of N, P and K were all positive for larger farms (LF) that had more cattle and derived a larger proportion of their income from off-farm activities, whereas on the medium farms (MF), small farms with cattle (SF1) and without cattle (SF2) balances were mostly negative. Sustainability of the farming system is driven by livestock, crop production, labour and access to off-farm income. Building private public partnerships around market-oriented crops can be an entry point for encouraging investment in use of external nutrient inputs to boost productivity in such African farming systems. However, intervention strategies should recognise the diversity and heterogeneity between farms to ensure efficient use of these external inputs
Impacts of heterogeneity in soil fertility on legume-finger millet productivity, farmers ' targeting and economic benefits
Targeting of integrated management practices for smallholder agriculture in sub-Saharan Africa is necessary due to the great heterogeneity in soil fertility. Experiments were conducted to evaluate the impacts of landscape position and field type on the biomass yield, N accumulation and N2-fixation by six legumes (cowpea, green gram, groundnut, mucuna, pigeonpea and soyabean) established with and without P during the short rain season of 2005. Residual effects of the legumes on the productivity of finger millet were assessed for two subsequent seasons in 2006 in two villages in Pallisa district, eastern Uganda. Legume biomass and N accumulation differed significantly (P <0.001) between villages, landscape position, field type and P application rate. Mucuna accumulated the most biomass (4.8–10.9 Mg ha-1) and groundnut the least (1.0–3.4 Mg ha-1) on both good and poor fields in the upper and middle landscape positions. N accumulation and amounts of N2-fixed by the legumes followed a similar trend as biomass, and was increased significantly by application of P. Grain yields of finger millet were significantly (P <0.001) higher in the first season after incorporation of legume biomass than in the second season after incorporation. Finger millet also produced significantly more grain in good fields (0.62–2.15 Mg ha-1) compared with poor fields (0.29–1.49 Mg ha-1) across the two villages. Participatory evaluation of options showed that farmers preferred growing groundnut and were not interested in growing pigeonpea and mucuna. They preferentially targeted grain legumes to good fields except for mucuna and pigeonpea which they said they would grow only in poor fields. Benefit-cost ratios indicated that legume-millet rotations without P application were only profitable on good fields in both villages. We suggest that green gram, cowpea and soyabean without P can be targeted to good fields on both upper and middle landscape positions in both villages. All legumes grown with P fertiliser on poor fields provided larger benefits than continuous cropping of millet
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