6,031 research outputs found
Alternative experimental evidence for chiral restoration in excited baryons
Given existing empirical spectral patterns of excited hadrons it has been
suggested that chiral symmetry is approximately restored in excited hadrons at
zero temperature/density (effective symmetry restoration). If correct, this
implies that mass generation mechanisms and physics in excited hadrons is very
different as compared to the lowest states. One needs an alternative and
independent experimental information to confirm this conjecture. Using very
general chiral symmetry arguments it is shown that strict chiral restoration in
a given excited nucleon forbids its decay into the N \pi channel. Hence those
excited nucleons which are assumed from the spectroscopic patterns to be in
approximate chiral multiplets must only "weakly" decay into the N \pi channel,
(f_{N^*N\pi}/f_{NN\pi})^2 << 1. However, those baryons which have no chiral
partner must decay strongly with a decay constant comparable with f_{NN\pi}.
Decay constants can be extracted from the existing decay widths and branching
ratios. It turnes out that for all those well established excited nucleons
which can be classified into chiral doublets N_+(1440) - N_-(1535), N_+(1710) -
N_-(1650), N_+(1720) - N_-(1700), N_+(1680) - N_-(1675), N_+(2220) - N_-(2250),
N_+(?) - N_-(2190), N_+(?) - N_-(2600), the ratio is (f_{N^*N\pi}/f_{NN\pi})^2
~ 0.1 or much smaller for the high-spin states. In contrast, the only well
established excited nucleon for which the chiral partner cannot be identified
from the spectroscopic data, N(1520), has a decay constant into the N\pi
channel that is comparable with f_{NN\pi}. This gives an independent
experimental verification of the chiral symmetry restoration scenario.Comment: 4 pp. A new footnote with an alternative proof of impossibility of
parity doublet decay into pi + N is added. To appear in Phys. Rev. Let
Kinetic energy cascades in quasi-geostrophic convection in a spherical shell
We consider triadic nonlinear interaction in the Navier-Stokes equation for
quasi-geostrophic convection in a spherical shell. This approach helps
understanding the origin of kinetic energy transport in the system and the
particular scheme of mode interaction, as well as the locality of the energy
transfer. The peculiarity of convection in the sphere, concerned with
excitation of Rossby waves, is considered. The obtained results are compared
with our previous study in Cartesian geometry
InGaAs/GaAs/alkanethiolate radial superlattices: Experimental
A radial InGaAs/GaAs/1-hexadecanethiol superlattice is fabricated by the
roll-up of a strained InGaAs/GaAs bilayer passivated with a molecular
self-assembled monolayer. Our technique allows the formation of multi-period
inorganic/organic hybrid heterostructures. This paper contains the detailed
experimental description of how to fabricate these structures.Comment: 2 pages, no figures, Version 2; minor changes (fixed typos and update
references
On the compatibility of causality and symmetry (Comments on "Analysis of causality in time-dependent density functional theory")
It is argued that there exists the only one inverse of the linear response
function , i.e. , which depends symmetrically of its
spatial-times variables, see M.K. Harbola, and A. Banerjee, Phys. Rev. A {\bf
60}, 5101 (1999). Some brief comments on this consideration are presented. We
show instead, that it is possible to construct the causal inverse also. At the
same time we confirm the main statement of M.K. Harbola and A. Banerjee that in
fact there is no contradiction between the symmetry and causality.Comment: 4 pages, LaTe
Stable Exact Solutions in Cosmological Models with Two Scalar Fields
The stability of isotropic cosmological solutions for two-field models in the
Bianchi I metric is considered. We prove that the sufficient conditions for the
Lyapunov stability in the Friedmann-Robertson-Walker metric provide the
stability with respect to anisotropic perturbations in the Bianchi I metric and
with respect to the cold dark matter energy density fluctuations. Sufficient
conditions for the Lyapunov stability of the isotropic fixed points of the
system of the Einstein equations have been found. We use the superpotential
method to construct stable kink-type solutions and obtain sufficient conditions
on the superpotential for the Lyapunov stability of the corresponding exact
solutions. We analyze the stability of isotropic kink-type solutions for string
field theory inspired cosmological models.Comment: 23 pages, v3:typos corrected, references adde
Accounting of 131l decomposition under retrospective assessment of its deposition on the basis of determination of 129l deposition
It is known that after the Chernobyl accident on the territories with deposition density of 137Cs less than 3.7x10" Bq/kg insufficient number of direct thyroid measurements for the public and a limited number of the spectrometrical measurements of 131l in soil were conducted. At the same time, in the case of availability of representative number of the estimates of the 131l ground deposition density for the territory under consideration, reliable estimates of the average dose to the thyroid for the public in a given settlement can be derived, for example for an adult population with further assessment of the doses for the residents of the other age-groups. In this regard, reconstruction of the ground deposition density of 131l (during the significant period of thyroid dose formation) on the basis of the determination of the ground deposition density of 129l is very helpful for reconstruction of the estimates of the thyroid dose for the residents of the settlements, for which the estimates of the 137Cs deposition density are available. However, to find a solution was necessary to resolve a specific but important task that distinguished from 129l (half-life is equal to 1.6x107 years) the level of 131l (half-life is equal to 8.04 days) was substantially decreasing during the period of thyroid dose formation. The
given article aimed a justification of approaches to account of radioactive decay of 131l in the course of determination of its ground deposition density on the basis of determination of the ground deposition density of 129l at the late stage after the accident
Bianchi Type III String Cosmological Models with Time Dependent Bulk Viscosity
Bianchi type III string cosmological models with bulk viscous fluid for
massive string are investigated. To get the determinate model of the universe,
we have assumed that the coefficient of bulk viscosity () is inversely
proportional to the expansion () in the model and expansion ()
in the model is proportional to the shear (). This leads to , and are constants. The behaviour of the model in presence
and absence of bulk viscosity, is discussed. The physical implications of the
models are also discussed in detail.Comment: 11 pages, no figur
Land Evaluation for improved Rice Production in Watari Irrigation Project Kano State, Nigeria
This study aimed at raising irrigated rice production in Watari Irrigation scheme, in Kano state, as to bridge the gap between the demand for rice and its supply. The food and Agricultural Organization FAO, (1985) frame work for land evaluation for irrigated rice production was employed, and the soil map of the study area has already been produced by Haskoning NigeriaLimited in 1987 and only those mapping units identified as suitable for irrigation were considered for the study. Six (6) Land mapping units were delineated and twenty six(26) sampling points considered with a single profile from each mapping unit and various soil augerings.These were evaluated with respect to their land qualities and characteristics which are then matched with the requirements and limitations for irrigated rice using the FAO, (1985) rating for suitability. The results of the study revealed three (3) suitability classes via; moderately suitable, marginally suitable and not suitable classes with some degree of limitations. However, the area has been found to be moderately suitableâ because of the larger area covered by the moderately suitable mapping units compare to the marginally suitable and not suitable mapping units. The limitations identified are those of stoniness, slope, texture, nutrient availability and drainability. The appropriate recommended management practices suggested to overcome these limitation and upgrade the suitability of the mapping units for increased rice production are; application of inorganic fertilizer, improve the low levels of nutrients and organic matter contents of the soil in the area and other recommendations include land leveling and conservation measures to control the effects oferosional hazards and slope steepness.Keywords: Suitability, Evaluation and Irrigated rice
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