A Machian Model of Dark Energy

Einstein believed that Mach's principle should play a major role in finding a meaningful spacetime geometry, though it was discovered later that his field equations gave some solutions which were not Machian. It is shown, in this essay, that the kinematical $\Lambda$ models, which are invoked to solve the cosmological constant problem, are in fact consistent with Mach's ideas. One particular model in this category is described which results from the microstructure of spacetime and seems to explain the current observations successfully and also has some benefits over the conventional models. This forces one to think whether the Mach's ideas and the cosmological constant are interrelated in some way.Comment: Received an Honorable mention in the Essay Contest-2002 sponsored by the Gravity Research Foundation; A paragraph added on how the model can explain the CMB anisotropy observations; To appear in the Classical and Quantum Gravit

On the Relativistic Formulation of Matter

A critical analysis of the relativistic formulation of matter reveals some surprising inconsistencies and paradoxes. Corrections are discovered which lead to the long-sought-after equality of the gravitational and inertial masses, which are otherwise different in general relativity. Realizing the potentially great impact of the discovered corrections, an overview of the situation is provided resulting from the newly discovered crisis, amid the evidences defending the theory.Comment: In press with Astrophys. Space Sci. (The final publication can be seen at springerlink.com

Non-monotonic diffusion rates in atom-optics L\'{e}vy kicked rotor

The dynamics of chaotic Hamiltonian systems such as the kicked rotor continues to guide our understanding of transport and localization processes. The localized states of the quantum kicked rotor decay due to decoherence effects if subjected to stationary noise. The associated quantum diffusion increases monotonically as a function of a parameter characterising the noise distribution. In this work, for the Levy kicked atom-optics rotor, it is experimentally shown that by tuning a parameter characterizing the Levy distribution, quantum diffusion displays non-monotonic behaviour. The parameters for optimal diffusion rates are analytically obtained and they reveal a good agreement with the cold atom experiments and numerics. The non-monotonicity is shown to be a quantum effect that vanishes in the classical limit.Comment: 5 pages, revte

Modeling Repulsive Gravity with Creation

There is a growing interest in the cosmologists for theories with negative energy scalar fields and creation, in order to model a repulsive gravity. The classical steady state cosmology proposed by Bondi, Gold and Hoyle in 1948, was the first such theory which used a negative kinetic energy creation field to invoke creation of matter. We emphasize that creation plays very crucial role in cosmology and provides a natural explanation to the various explosive phenomena occurring in local (z<0.1) and extra galactic universe. We exemplify this point of view by considering the resurrected version of this theory - the quasi-steady state theory, which tries to relate creation events directly to the large scale dynamics of the universe and supplies more natural explanations of the observed phenomena. Although the theory predicts a decelerating universe at the present era, it explains successfully the recent SNe Ia observations (which require an accelerating universe in the standard cosmology), as we show in this paper by performing a Bayesian analysis of the data.Comment: The paper uses an old SNeIa dataset. With the new improved data, for example the updated gold sample (Riess et al, astro-ph/0611572), the fit improves considerably (\chi^2/DoF=197/180 and a probability of goodness-of-fit=18%

High-resolution images of five radio quasars at early cosmological epochs

Context: Until now, there have only been seven quasars at z>4.5 whose the high-resolution radio structure had been studied in detail with Very Long Baseline Interferometry (VLBI) imaging. Aims: We almost double the number of VLBI-imaged quasars at these high redshifts with the aim of studying their redshift-dependent structural and physical properties in a larger sample. Methods: We observed five radio quasars (J0813+3508, J1146+4037, J1242+5422, J1611+0844, and J1659+2101) at 4.5<z<5 with the European VLBI Network (EVN) at 1.6 GHz on 29 October 2008 and at 5 GHz on 22 October 2008. The angular resolution achieved ranges from 1.5 to 25 milli-arcseconds (mas), depending on the observing frequency, the position angle in the sky, and the source's celestial position. Results: The sources are all somewhat extended on mas scales, but compact enough to be detected at both frequencies. With one exception of a flat-spectrum source (J1611+0844), their compact emission is characterised by a steep radio spectrum. We found no evidence of Doppler-boosted radio emission in the quasars in our sample. The radio structure of one of them (J0813+3508) is extended to ~7", which corresponds to 43 kpc projected linear size. Many of the highest redshift compact radio sources are likely to be young, evolving objects, far-away cousins of the powerful gigahertz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that populate the Universe at lower redshifts.Comment: 7 pages, 2 figures, accepted for Astronomy & Astrophysic

Assessment of genetic variability and character association for grain yield and its component traits in bread wheat (Triticum aestivum L.)

A study was conducted for estimating genetic variability and characters association for eleven yield components using 169 genotypes (13 parents, 78 F1 and 78 F2) of bread wheat through half-diallel mating design during rabi season 2012-13 and 2013-14. The genetic variability, heritability in broad sense, genetic advance, correlation coefficients and path analysis were carried out for the assessment of genotypes through eleven yield component traits namely; days to 50% flowering, days to maturity, plant height, spike length, number of effective tillers per plant, number of grains per spikelet, number of grains per spike, 1000-grain weight, biological yield per plant, harvest index and grain yield per plant. Analysis of variance showed significant differences (at1% level of significance) for all the traits under study in both the generations (F1 and F2). The phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were high for plant height followed by number of effective tillers per plant, biological yield per plant, grain yield per plant, while high heritability coupled with high genetic advance were recorded for plant height and spike length in both F1 and F2 generations, respectively. Grain yield per plant was positively and significantly associated with a number of effective tillers per plant, spike length, number of grains per spike, 1000-grain weight, biological yield per plant and harvest index while significantly but negatively associated with plant height. Path analysis revealed that the traits namely biological yield per plant, number of effective tillers per plant, number of grains per spike, plant height and harvest index exhibited positive direct effects on grain yield at both phenotypic and genotypic level in both generation (F1 and F2). These results, thereby suggests that yield improvement in breads wheats could be possible by emphasizing these traits while making selections in early generations

Analysis of genetic diversity among tropical and subtropical maize inbred lines using SSR markers

Genetic diversity of 24 tropical and subtropical elite maize lines was assessed at molecular level employ-ing 42 Simple Sequence Repeats. A total of 107 alleles with an average of 2.55 alleles per locus were detected. The Polymorphism Information Content (PIC) values of 42 SSR loci ranged from 0.08 (UMC1428) to 0.68 (UMC2189 and UMC2332) with the overall calculated PIC mean value of 0.44, whereas the Discrimination Rate (DR) value for SSR markers ranged from 0.09 (UMC2089) to 0.42 (UMC1311) with the average DR value of 0.26. Pair-wise genet-ic similarity (GS) values, calculated by Jaccard’s coefficients, ranged between 0.25 and 0.78 with a mean genetic similarity of 0.63, indicating the existence of adequate amount of genetic divergence among the genotypes selected for the study. The cluster dendrogram separated all the inbred lines into six main clusters with sub clusters based on genetic similarity. Factorial analysis also confirmed a nearly similar pattern for grouping these inbred lines as pre-sented by cluster dendrogram. In this study, SSR markers were found to be powerful tool for detection of genetic diversity in maize inbred lines. These findings could provide information for effective utilization of these materials for development of maize hybrids as well as for genetic improvement of inbred lines