3,515 research outputs found
Dark Energy and the Statistical Study of the Observed Image Separations of the Multiply Imaged Systems in the CLASS Statistical Sample
The present day observations favour a universe which is flat, accelerated and
composed of matter (baryonic + dark) and of a negative
pressure component, usually referred to as dark energy or quintessence. The
Cosmic Lens All Sky Survey (CLASS), the largest radio-selected galactic mass
scale gravitational lens search project to date, has resulted in the largest
sample suitable for statistical analyses. In the work presented here, we
exploit observed image separations of the multiply imaged lensed radio sources
in the sample. We use two different tests: (1) image separation distribution
function of the lensed radio sources and (2)
{\dtheta}_{\mathrm{pred}} vs {\dtheta}_{\mathrm{obs}} as observational
tools to constrain the cosmological parameters and \Om. The results are
in concordance with the bounds imposed by other cosmological tests.Comment: 20 pages latex; Modified " Results and Discussion " section, new
references adde
Light propagation in nanorod arrays
We study propagation of TM- and TE-polarized light in two-dimensional arrays
of silver nanorods of various diameters in a gelatin background. We calculate
the transmittance, reflectance and absorption of arranged and disordered
nanorod arrays and compare the exact numerical results with the predictions of
the Maxwell-Garnett effective-medium theory. We show that interactions between
nanorods, multipole contributions and formations of photonic gaps affect
strongly the transmittance spectra that cannot be accounted for in terms of the
conventional effective-medium theory. We also demonstrate and explain the
degradation of the transmittance in arrays with randomly located rods as well
as weak influence of their fluctuating diameter. For TM modes we outline the
importance of skin-effect, which causes the full reflection of the incoming
light. We then illustrate the possibility of using periodic arrays of nanorods
as high-quality polarizers.Comment: 6 pages, 7 figure
The consequences of SU(3) colorsingletness, Polyakov Loop and Z(3) symmetry on a quark-gluon gas
Based on quantum statistical mechanics we show that the color singlet
ensemble of a quark-gluon gas exhibits a symmetry through the normaized
character in fundamental representation and also becomes equivalent, within a
stationary point approximation, to the ensemble given by Polyakov Loop. Also
Polyakov Loop gauge potential is obtained by considering spatial gluons along
with the invariant Haar measure at each space point. The probability of the
normalized character in vis-a-vis Polyakov Loop is found to be maximum
at a particular value exhibiting a strong color correlation. This clearly
indicates a transition from a color correlated to uncorrelated phase or
vise-versa. When quarks are included to the gauge fields, a metastable state
appears in the temperature range due to the
explicit symmetry breaking in the quark-gluon system. Beyond
MeV the metastable state disappears and stable domains appear. At low
temperature a dynamical recombination of ionized color charges to a
color singlet confined phase is evident along with a confining
background that originates due to circulation of two virtual spatial gluons but
with conjugate phases in a closed loop. We also discuss other possible
consequences of the center domains in the color deconfined phase at high
temperature.Comment: Version published in J. Phys.
Replicating Nanostructures on Silicon by Low Energy Ion Beams
We report on a nanoscale patterning method on Si substrates using
self-assembled metal islands and low-energy ion-beam irradiation. The Si
nanostructures produced on the Si substrate have a one-to-one correspondence
with the self-assembled metal (Ag, Au, Pt) nanoislands initially grown on the
substrate. The surface morphology and the structure of the irradiated surface
were studied by high-resolution transmission electron microscopy (HRTEM). TEM
images of ion-beam irradiated samples show the formation of sawtooth-like
structures on Si. Removing metal islands and the ion-beam induced amorphous Si
by etching, we obtain a crystalline nanostructure of Si. The smallest
structures emit red light when exposed to a UV light. The size of the
nanostructures on Si is governed by the size of the self-assembled metal
nanoparticles grown on the substrate for this replica nanopatterning. The
method can easily be extended for tuning the size of the Si nanostructures by
the proper choice of the metal nanoparticles and the ion energy in
ion-irradiation. It is suggested that off-normal irradiation can also be used
for tuning the size of the nanostructures.Comment: 12 pages, 7 figures, regular paper submitted to Nanotechnolog
Delicate f(R) gravity models with disappearing cosmological constant and observational constraints on the model parameters
We study the theory of gravity using metric approach. In particular we
investigate the recently proposed model by Hu-Sawicki, Appleby Battye and
Starobinsky. In this model, the cosmological constant is zero in flat space
time. The model passes both the Solar system and the laboratory tests. But the
model parameters need to be fine tuned to avoid the finite time singularity
recently pointed in the literature. We check the concordance of this model with
the and baryon acoustic oscillation data. We find that the model
resembles the CDM at high redshift. However, for some parameter values
there are variations in the expansion history of the universe at low redshift.Comment: 16 pages and 9 figures, typos corrected, few references and minor
clarifications added, revised version to appera in PR
Band Structure of the Fractional Quantum Hall Effect
The eigenstates of interacting electrons in the fractional quantum Hall phase
typically form fairly well defined bands in the energy space. We show that the
composite fermion theory gives insight into the origin of these bands and
provides an accurate and complete microscopic description of the strongly
correlated many-body states in the low-energy bands. Thus, somewhat like in
Landau's fermi liquid theory, there is a one-to-one correspondence between the
low energy Hilbert space of strongly interacting electrons in the fractinal
quantum Hall regime and that of weakly interacting electrons in the integer
quantum Hall regime.Comment: 10 page
Integrated Nutrient Management for Natural Grasslands of Mid-Hills of Himalayas
Livestock rearing is an important pursuit in mountain farming in India and plays a crucial role throughout the country. The preponderance of marginal and small landholdings (about 82%) in hilly regions does not allow the farmers to allocate even a small part of their land exclusively for forage production. In Himachal Pradesh state of India about 1.16 m ha (20% of the total area) is under permanent pastures and other grazing lands and none of the natural grasslands are fertilised in any form. Existing grasslands have deteriorated to such an extent that their carrying capacity is only 1.05 ACU (Adult Cattle Unit, with an average body weight of 350 kg)/ha (Vashist et al., 2000). Biofertiliser-based technologies could be appropriate and cost effective approaches that are easy to adopt and eco-friendly. Response may arise from increased populations of phosphate solubilisers in the rhizosphere in P- deficient soils resulting in mobilisation of insoluble phosphorus (Raghu & Mac Rac, 1967). The study was undertaken with the main objectives of assessing the effects of biofertilisers on productivity and quality of natural grassland and the level of N and P substitution by biofertilisers
Agricultural water management interventions for enhancing water resources availability, cropping, intensity and various ecosystem services in Bundelkhand region of Central India
Bundelkhand region of Central India is hot spot of water scarcity, land degradation, low cropping intensity,
poor crop and livestock productivity and poor socio-economic status. Nearly 70% of the population of
Bundelkhand is dependent on agriculture and allied sectors for its livelihood. A National Sample Survey
report of 2017 shows that the per capita income in Bundelkhand is nearly ₹25,000, far below the national
average (₹103,000) and those of Uttar Pradesh (₹43,800) and neighboring Madhya Pradesh (₹56,200) and
Rajasthan (₹76,900). Given that strategies that focus on transforming agricultural and allied sectors are
key to improving livelihoods of rural populations, the Government of India laid the pathway for doubling
farmer’s incomes by 2022
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