Effect of realistic interatomic interactions and two-body correlation on the heat capacity of a trapped BEC

An approximate many-body theory has been used to calculate the heat capacity and the condensate fraction of a BEC with effective repulsive interaction. The effect of interactions has been analyzed and compared with the non-interacting case. It has been found that the repulsive interaction lowers the critical temperature from the value found in the non-interacting case. The difference between the critical temperatures increases with the increase in the total number of atoms in the trap.Comment: 15 pages, 5 figure

The Complex Time WKB Approximation And Particle Production

The complex time WKB (CWKB) approximation has been an effective technique to understand particle production in curved as well as in flat spacetime. Earlier we obtained the standard results on particle production in time dependent gauge in various curved spacetime. In the present work we generalize the technique of CWKB to the equivalent problems in space dependent gauge. Using CWKB, we first obtain the gauge invariant result for particle production in Minkowski spacetime in strong electric field. We then carry out particle production in de-Sitter spacetime in space dependent gauge and obtain the same result that we obtained earlier in time dependent gauge. The results obtained for de-Sitter spacetime has a obvious extension to particle production in black hole spacetime. It is found that the origin of Planckian spectrum is due to repeated reflections between the turning points. As mentioned earlier, it is now explicitly shown that particle production is accompanied by rotation of currents.Comment: 12 pages, Revte

On Modified Gravity

We consider some aspects of nonlocal modified gravity, where nonlocality is of the type $R \mathcal{F}(\Box) R$. In particular, using ansatz of the form $\Box R = c R^\gamma,$ we find a few $R(t)$ solutions for the spatially flat FLRW metric. There are singular and nonsingular bounce solutions. For late cosmic time, scalar curvature R(t) is in low regime and scale factor a(t) is decelerated. R (t) = 0 satisfies all equations when k = -1.Comment: added references; made some clarifications; 8 page

Study of QCD generalized ghost dark energy in FRW universe

A phenomenological generalized ghost dark energy model has been studied under the framework of FRW universe. In ghost dark energy model the energy density depends linearly on Hubble parameter (H) but in this dark energy model, the energy density contains a the sub-leading term which is depends on $\mathcal{O} (H^2)$, so the energy density takes the form $\rho_D=\alpha H+ \beta H^2$, where $\alpha$ and $\beta$ are the constants. The solutions of the Friedman equation of our model leads to a stable universe. We have fitted our model with the present observational data including Stern data set. With the help of best fit results we find the adiabatic sound speed remains positive throughout the cosmic evolution, that claims the stability of the model. The flipping of the signature of deceleration parameter at the value of scale factor $a=0.5$ indicates that the universe is at the stage of acceleration i.e. de Sitter phase of the universe at late time. Our model shows that the acceleration of the universe begin at redshift $z_{ace}\approx 0.617$ and the model is also consistent with the current observational data.Comment: 9 pages, 9 figure

On-farm impact analysis of resource conservation technology on wheat at Tarai-Teesta Flood plain of Eastern Indo-Gangetic Plain (IGP)

Adoption of resource conservation technologies (RCT) may improve the productivity, reduce cost and sustainability of wheat production in the irrigated areas of eastern Indo-Gangetic plains (IGP) of South Asia. Critical on –farm study on factors favouring adoption and non-adoption is required. Findings from an on-farm trial conducted during 2005-2009 are used to evaluate the on-farm impacts of zero tillage (ZT) in wheat from three sites at Tarai-Teesta flood plain of eastern IGP. On an average, there was 11.54% increase in productivity in ZT wheat over conventional tilled (CT) wheat. Water productivity increased from 1.99 kg m-3 in CT to 2.73 kg m-3 in ZT due to lower estimated water use (1147 m3 ha-1 in ZT than 1435 m3 ha-1 in CT) and higher productivity (3.38 t ha-1 in ZT than 3.03 t ha-1 in CT). Saving in tractor operation and diesel use in farmers’ ZT wheat fields were 3.23 and 19.09 hours ha-1. Sowing can be done earlier by one week through adoption of ZT machine for better utilization of limited winter. Savings in ZT on farmers’ fields were in the components of land preparation (1938 Rs ha-1), seed (462 Rs ha-1), nitrogen (269 Rs ha-1), phosphate fertilizer (104 Rs ha-1) and irrigation (380 Rs ha-1) over conventional wheat cultivation. Availability of zero-till seeder and its servicing, skilled operator and sometimes reluctance of local tiller operator for apprehension of lower earnings from single tillage pass are also revealed as the factors of non-adoption. More such in-depth studies should be conducted on site-specific basis so that it can be replicated more widely in areas for the benefit of the farming community