Role of Hund's coupling in stabilization of the (0,pi) ordered SDW state within the minimal two-band model for iron pnictides

Spin wave excitations and stability of the (0,pi) ordered SDW state are investigated within the minimal two-band model for iron pnictides including a Hund's coupling term. The SDW state is shown to be stable in two distinct doping regimes --- finite hole doping in the lower SDW band for small second neighbour hoppings, and small electron doping in the upper SDW band for comparable first and second neighbour hoppings. In both cases, Hund's coupling strongly stabilizes the SDW state due to generation of additional ferromagnetic spin couplings involving the inter-orbital part of the particle-hole propagator. Spin wave energies for the two-band model are very similar to the one-band t-t' Hubbard model results obtained earlier, and are in agreement with inelastic neutron scattering studies of iron pnictides.Comment: 9 pages, 4 figure

Interaction Between The Broad-lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands

The diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond with electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (~30 days) timescales. The 4428 and 6283 Angstrom DIB features get weaker with time, whereas the 5780 Angstrom feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of the DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers.Comment: 6 pages, 3 figures, accepted for publication in ApJ

The dark nature of GRB 051022 and its host galaxy

We present multiwavelength (X-ray/optical/near-infrared/millimetre) observations of GRB 051022 between 2.5 hours and ~1.15 yr after the event. It is the most intense gamma-ray burst (~ 10^-4 erg cm^-2) detected by HETE-2, with the exception of the nearby GRB 030329. Optical and near infrared observations did not detect the afterglow despite a strong afterglow at X-ray wavelengths. Millimetre observations at Plateau de Bure (PdB) detected a source and a flare, confirming the association of this event with a moderately bright (R = 21.5) galaxy. Spectroscopic observations of this galaxy show strong [O II], Hbeta and [O III] emission lines at a redshift of 0.809. The spectral energy distribution of the galaxy implies Av (rest frame) = 1.0 and a starburst occuring ~ 25 Myr ago, during which the star-forming-rate reached >= 25 Msun/yr. In conjunction with the spatial extent (~ 1'') it suggests a very luminous (Mv = - 21.8) blue compact galaxy, for which we also find with Z Zsun. The X-ray spectrum shows evidence of considerable absorption by neutral gas with NH, X-ray = 3.47(+0.48/-0.47) x 10^22 cm^-2 (rest frame). Absorption by dust in the host galaxy at z = 0.809 certainly cannot account for the non-detection of the optical afterglow, unless the dust-to-gas ratio is quite different than that seen in our Galaxy (i.e. large dust grains). It is likely that the afterglow of the dark GRB 051022 was extinguished along the line of sight by an obscured, dense star forming region in a molecular cloud within the parent host galaxy. This galaxy is different from most GRB hosts being brighter than L* by a factor of 3. We have also derived a SFR ~ 50 Msun/yr and predict that this host galaxy will be detected at sub-mm wavelengths.Comment: 7 Pages, 7 figures. Accepted in Astronomy and Astrophysic

GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

Long duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of a massive star. Over the last forty years, our understanding of the GRB phenomenon has progressed dramatically; nevertheless, fortuitous circumstances occasionally arise that provide access to a regime not yet probed. GRB 080319B presented such an opportunity, with extraordinarily bright prompt optical emission that peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. It was captured in exquisite detail by wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous gamma-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. Here we show that the prompt optical and gamma-ray emissions from this event likely arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. The chromatic behaviour of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs. These circumstances can explain the extreme properties of this GRB.Comment: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 200

The internal consistency reliability of the Santosh-Francis Scale of Attitude toward Hinduism among students in India

The Santosh–Francis Scale of Attitude toward Hinduism was originally developed and tested among Hindus in the UK as part of a programme designed to assess religious affect across faith traditions. The present study tests the internal consistency reliability and construct validity of the instrument among 149 students in Karnatak University Dharwad (74 males and 75 females), India. The data demonstrated an alpha coefficient of .90, suggesting a high level of internal consistency reliability and commending the instrument for further application within Hindu communities

Morphological Properties of Red and Black Soils of Selected Benchmark Spots in Semi-Arid Tropics of India: Global Theme on Agroecosystems Report no. 21

Morphological properties of red and black soils are described. Soil depth, color, texture, consistence, structure, roots, coarse fragments, nodules, effervescence, slickensides, cracks and clay cutans are described in sub- humid (moist and dry), semi-arid (moist, dry) and arid ecosystems. Soils under high management are darker in color indicating more soil organic carbon content. Wet consistence such as very sticky and very plastic corresponds with those horizons in black soils showing well developed slickensides. Firm moist consistence may indicate development of sodicity problems provided there are no or very less amount of soil modifiers such as zeolites and gypsum. Higher root density in soils corresponds with lower degree of CaCO3 content as indicated by slighteffervescence with dilute HCl in the field. Black soils contained coarse fragments of 3-8%, 1-10%, 1-10% and 5-15% in sub-humid (moist), semi-arid (moist), semi-arid (dry) and arid bioclimatic system, respectively. In general, the degree of effervescence is in line with size and quantity of coarse fragments and calcium concretions observed in the field. In general black soils under high management show slickensides at lower depths. With decrease in mean annual rainfall, the depth of occurrence of slickensides decreases from 60 cm in sub-humid (moist) to 30 cm in semi-arid (dry) bioclimate. Management interventions including irrigation in drier tracts push the slickensides further down in the profile. The formation of Sodic Haplusterts indicate poor organic carbon accumulation but a very high inorganic carbon sequestration in soils of dry part of the arid bioclimatic system. It manifests natural chemical degradation of soils with mean annual rainfall of <550 mm

Characterization of Benchmark Spots of Selected Red and Black Soils in Semi-Arid Tropics of India for Identifying Systems for Carbon Sequestration and Increased Productivity in Semi-Arid Tropical Environments: Global Theme on Agroecosystems Report no. 42

Fifty two pedons spread over 28 Benchmark (BM) spots were studied in different systems viz. agricultural, horticultural, forest and wasteland. The agricultural system represents dominant crops namely cereals, soybean and cotton. The horticultural system represents mandarins. The forest systems represent teak (Tectona sp.) and sal (Shorea sp.). The selection of BM spots were limited to a mean annual rainfall (MAR) range from 1448 to 520 mm in semi-arid tropics, India and encompass various bioclimatic systems such as sub-humid (moist) (MAR >1200 mm), sub-humid (dry) (MAR 1200-1000 mm), semi-arid (dry) (1000-850 mm), semi-arid (moist) (850-550 mm) and arid (<550 mm). In order to find out the level of carbon (organic and inorganic) in soils as influenced by different land use systems, the quality and quantity of (soil) substrates require to be similar. Judging by dominantly clayey and smectitic nature of black soils (Vertisols and their intergrades) and the associated red soils, they were selected for the present study. The soils were characterized in terms of morphological, physical and chemical properties with the data sets generated in the field and laboratory. Each profile was also characterized by the climatic data, indicating monthly potential evapotranspiration (PET), rainfall, temperature and length of growing period (LGP) data. The exact landscape situations, cropping patterns and typical soil profiles depicted through photographs further indicate the exact location of each spot studied in this project. The present document attempts to find out various relation of morphological, physical and chemical properties of soils as far as both organic and inorganic carbon sequestration are concerned. The present document also helps in estimating carbon stock in different system under various bioclimatic zones in semi-arid tropics, India as detailed in subsequent working reports