266 research outputs found
Iso-curvature fluctuations through axion trapping by cosmic string wakes
We consider wake-like density fluctuations produced by cosmic strings at the
quark-hadron transition in the early universe. We show that low momentum axions
which are produced through the radiation from the axionic string at an earlier
stage, may get trapped inside these wakes due to delayed hadronization in these
overdense regions. As the interfaces, bordering the wakes, collapse, the axions
pick-up momentum from the walls and finally leave the wake regions. These
axions thus can produce large scale iso-curvature fluctuations. We have
calculated the detailed profile of these axionic density fluctuations and
discuss its astrophysical consequences.Comment: 23 pages, 4 figures, RevTe
Baryon Inhomogeneity Generation in the Quark-Gluon Plasma Phase
We discuss the possibility of generation of baryon inhomogeneities in a
quark-gluon plasma phase due to moving Z(3) interfaces. By modeling the
dependence of effective mass of the quarks on the Polyakov loop order
parameter, we study the reflection of quarks from collapsing Z(3) interfaces
and estimate resulting baryon inhomogeneities in the context of the early
universe. We argue that in the context of certain low energy scale inflationary
models, it is possible that large Z(3) walls arise at the end of the reheating
stage. Collapse of such walls could lead to baryon inhomogeneities which may be
separated by large distances near the QCD scale. Importantly, the generation of
these inhomogeneities is insensitive to the order, or even the existence, of
the quark-hadron phase transition. We also briefly discuss the possibility of
formation of quark nuggets in this model, as well as baryon inhomogeneity
generation in relativistic heavy-ion collisions.Comment: 11 pages, 2 figures, revtex4, more detailed discussion added about
formation and evolution of Z(3)domain walls in the univers
Genetic variability, characters association and path analysis for yield and fruit quality components in Brinjal
The experiment was done at AB District Seed Farm, BCKV, Kalyani Simanta, West-Bengal, India during autumn-winter 2013-14 and 2014-15. The characters that exhibited higher Phenotypic and Genotypic Co-efficient of variation values were number of fruits per plant (76.86, 75.63%), fruit weight (43.88, 41.34%), harvest index (23.57, 22.29%), fruit yield per plant (53.61, 51.17%), anthocyanin in peel, total phenols and DPPH (2,2-diphenyl-l-picryl hydrazyl) free radical scavenging (FRS) capacity indicating that a greater amount of genetic variability was present for these characters which provide greater scope for selection. High heritability coupled with high genetic advance as percent of mean was observed for the characters like plant height, days to 1st flowering, days to 50% flowering, number of fruits per plant, fruit weight, harvest index, fruit yield per plant, total sugar, anthocyanin in peel, total phenols and DPPH FRS capacity depicting that these traits were under the strong influence of additive gene action and hence simple selection based on phenotypic performance of these traits would be more effective. Fruit yield per plant showed highly positive significant correlation with number of primary branches per plant, number of fruits per plant, harvest index, vitamin-A and total phenols and significant negative correlation with days to 1st flowering, TSS, total sugars and total protein. Number of fruits per plant imparted the highest positive direct effect on yield followed by harvest index, fruit weight, days to 50% flowering and anthocyanin in peel. Number of fruits per plant and days to flowering were emerged as the main casual factors for positive or negative association of several characters with fruit yield per plant. Therefore, selection for fruit yield per plant based on these characters would be reliable
Baryon inhomogeneity generation via cosmic strings at QCD scale and its effects on nucleosynthesis
We have earlier shown that cosmic strings moving through the plasma at the
time of a first order quark-hadron transition in the early universe can
generate large scale baryon inhomogeneities. In this paper, we calculate
detailed structure of these inhomogeneities at the quark-hadron transition. Our
calculations show that the inhomogeneities generated by cosmic string wakes can
strongly affect nucleosynthesis calculations. A comparison with observational
data suggests that such baryon inhomogeneities should not have existed at the
nucleosynthesis epoch. If this disagreement holds with more accurate
observations, then it will lead to the conclusions that cosmic string formation
scales above GeV may not be consistent with nucleosynthesis
and CMBR observations. Alternatively, some other input in our calculation
should be constrained, for example, if the average string velocity remains
sufficiently small so that significant density perturbations are never produced
at the QCD scale, or if strings move ultra-relativistically so that string
wakes are very thin, trapping negligible amount of baryons. Finally, if
quark-hadron transition is not of first order then our calculations do not
apply.Comment: 24 pages, 5 figures, minor changes, version to appear in Phys. Rev.
Soil Quality Parameters and Carbon Stock as Influenced by Fodder Grasses and Organic Amendments in an Alfisol of Northeastern India
Intensive tillage, cultivation along the slope, low input, minimal nutrient replacement and high rainfall are among major causes of land degradation in the north eastern hill (NEH) region (Ghosh et al. 2009). Maintaining and enhancing soil quality are crucial to sustaining agricultural productivity and environmental quality (Lal, 2004). Continuous cropping, without use of conservation-effective measures, has negative effects on the soil and environment (e.g., loss of SOC, soil erosion, water pollution). Thus, soil management methods are needed that enhance use efficiency of inputs, reduce losses and minimize adverse impacts on the environment (Bilalis et al. 2009). Perennial grasses provide year- round ground cover, which reduces run-off and soil erosion from sloping land (Ghosh et al. 2009).
Cultivation of forages in degraded and sloping lands not only supply green palatable fodders to livestocks but also rehabilitates the degraded soils by improving physico-chemical properties. Forages have strong root systems compared to field crops (such as rice, maize etc.), protect soil and improve aggregation (Ghosh et al. 2009). Soils under perennial grasses and those which are undisturbed for a long time are potential C sinks because the grasses add organic matter (OM) to soils through root growth, and decline in OM decomposition because of lack of tillage. Further, conversion of degraded cropland soils to forages and perennial grasses lead to C sequestration (Grandy and Robertson, 2007).
Thus, present investigation was conducted with the objective to assess the impact of perennial forage grasses and organic amendments on soil properties and C-sequestration potential
Cosmic string induced sheet like baryon inhomogeneities at quark-hadron transition
Cosmic strings moving through matter produce wakes where density is higher
than the background density. We investigate the effects of such wakes occurring
at the time of a first order quark-hadron transition in the early universe and
show that they can lead to separation of quark-gluon plasma phase in the wake
region, while the region outside the wake converts to the hadronic phase.
Moving interfaces then trap large baryon densities in sheet like regions which
can extend across the entire horizon. Typical separation between such sheets,
at formation, is of the order of a km. Regions of baryon inhomogeneity of this
nature, i.e. having a planar geometry, and separated by such large distance
scales, appear to be well suited for the recent models of inhomogeneous
nucleosynthesis to reconcile with the large baryon to photon ratio implied by
the recent measurements of the cosmic microwave background power spectrum.Comment: 8 pages, 3 figure
Blood flow peculiarities in vessels bifurcation
In this article we study the blood flow in models of branching blood vessels. Blood is a heterogeneous fluid and owing to the complex composition (erythrocytes, platelets, leukocytes, plasma) and the presence of special rheological properties (viscosity, pseudoplasticity, thixotropy), it can be attributed to non-Newtonian fluids. Red blood cells, called erythrocytes, responsible for transporting oxygen to tissues; white blood cells (platelets) for the regulation of the coagulation system activity. All blood components tend to deform and orientate in the stream and gather in clusters, which introduces significant changes in the behavior of blood flow. In the simplest terms, blood can be considered as a suspension of blood cells in physiological solution. The red cells are able to accumulate in the molecular chain and modify its configuration (shape and orientation in the flow). In our study, the blood flow simulation is implemented using rheological viscoelastic FENE-P model. It predicts the properties corresponding to real biological fluid such as the anomaly of viscosity, variable longitudinal viscosity and the finite time of relaxation of stresses. Governing parameters of the flows of such fluids is the Weissenberg number We, which characterizes the ratio of viscous to elastic properties, the Reynolds number Re describing the ratio of inertial to viscous properties, the ability of erythrocytes to change their orientation in the flow, the degree of disentanglement of the chains L2 and the coefficient of retardation characterizing the concentration of red blood cells. This article discusses the loss of symmetry of the fluid flow under given values of model parameters
Theoretical and experimental evidence of a site-selective Mott transition in Fe2O3 under pressure
We provide experimental and theoretical evidence for a novel type of
pressure-induced insulator-metal transition characterized by site-selective
delocalization of the electrons. M\"ossbauer spectroscopy, X-ray diffraction
and electrical transport measurements on FeO to 100 GPa, along with
dynamical mean-field theory (DFT+DMFT) calculations, reveal this site-selective
Mott transition between 50 and 68 GPa, such that the metallization can be
described by (^\rm{VI}Fe)O [ structure]
(^\rm{VIII}FeFe^\rm{M})O [ structure]
(^\rm{VI}Fe^\rm{M})O [
structure]. Within the crystal structure, characterized by two
distinct coordination sites (VI and VIII), we observe equal abundances of
ferric ions (Fe) and ions having delocalized electrons (Fe^\rm{M}),
and only at higher pressures is a fully metallic structure obtained, all
at room temperature. The transition is characterized by
delocalization/metallization of the electrons on half the Fe sites, with a
site-dependent collapse of local moments. Above 50 GPa, FeO is a
strongly correlated metal with reduced electron mobility (large band
renormalizations) of m*/m4 and 6 near the Fermi level. Upon
decompression, we observe a site-selective (metallic) to conventional Mott
insulator phase transition (^\rm{VIII}FeFe^\rm{M})O
(^\rm{VIII}FeFe)O within the same structure, indicating a decoupling of
the electronic and lattice degrees of freedom, characteristic of a true Mott
transition. Our results show that the interplay of electronic correlations and
lattice may result in rather complex behavior of the electronic structure and
magnetic state.Comment: 18 pages, 5 figure
Heavy ion physics
The 8th workshop on high energy physics phenomenology (WHEPP-8) was held at the Indian Institute of Technology, Mumbai, India during January 5-16, 2004. One of the four working groups, group III was dedicated to QCD and heavy ion physics (HIC). The present manuscript gives a summary of the activities of group III during the workshop (see also [1] for completeness). The activities of group III were focused to understand the collective behaviours of the system formed after the collisions of two nuclei at ultra-relativistic energies from the interactions of the elementary degrees of freedom, i.e. quarks and gluons, governed by non-abelian gauge theory, i.e. QCD. This was initiated by two plenary talks on experimental overview of heavy ion collisions and lattice QCD and several working group talks and discussions
Measuring Cosmic Defect Correlations in Liquid Crystals
From the theory of topological defect formation proposed for the early
universe, the so called Kibble mechanism, it follows that the density
correlation functions of defects and anti-defects in a given system should be
completely determined in terms of a single length scale , the relevant
domain size. Thus, when lengths are expressed in units of , these
distributions should show universal behavior, depending only on the symmetry of
the order parameter, and space dimensions. We have verified this prediction by
analyzing the distributions of defects/anti-defects formed in the
isotropic-nematic phase transition in a thin layer of nematic liquid crystals.
Our experimental results confirm this prediction and are in reasonable
agreement with the results of numerical simulations.Comment: 15 pages, 4 figures, minor changes, few new references adde
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