Variable Modified Chaplygin Gas and Accelerating Universe

In this letter, I have proposed a model of variable modified Chaplygin gas and shown its role in accelerating phase of the universe. I have shown that the equation of state of this model is valid from the radiation era to quiessence model. The graphical representations of statefinder parameters characterize different phase of evolution of the universe. All results presented in the letter concerns the case $k=0$.Comment: 7 Latex pages, 5 figures, revtex styl

A Quintessence Problem in Self-interacting Brans-Dicke Theory

A quintessence scalar field in self-interacting Brans-Dicke theory is shown to give rise to a non-decelerated expansion of the present universe for open, flat and closed models. Along with providing a non-decelerating solution, it can potentially solve the flatness problem too.Comment: 8 Latex pages, No figure, Revtex styl

A Quintessence Problem in Brans-Dicke Theory with Varying Speed of Light

It is shown that minimally coupled scalar field in Brans-Dicke theory with varying speed of light can solve the quintessence problem and it is possible to have a non-decelerated expansion of the present universe with BD-theory for anisotropic models without any matter.Comment: 8 Latex pages, 6 figures, Revtex styl

A review of challenges from increasing renewable generation in the Indian Power System

About 70% of India’s current energy mix comprises of coal, and the increase in generation from renewable energy (RE) sources is affecting the health of the power system. We investigated this effect through a cross-sectional of asset utilisation, cost and the social disruption caused by accelerating RE into the Indian Power System. We also derived a challenge-roadmap for the power system using bibliometric analysis. The review-driven interpretivist results revealed that increasing RE generation is pushing the coal plants to operate in low-loading conditions, causing heightened wear and tear of the plant as they are not suitable for flexible operation. It had tremendously increased the operation and maintenance costs of the brownfield plants. While there is a growing scope for cross border trade of electricity, the existing regulatory mechanism poses severe implementation challenges. Social disruption due to shift from coal-economy illustrated a holistic view of the political economy of the Indian power system that can potentially cause large-scale conflict and disrupt the national economy at an unprecedented scale. Policy implications outlined by our study for the draft Electricity (Amendment) Bill 2020 include scoping a socio-technical framework which supports just energy transition through better financial support mechanisms for flexible operation of coal plants. Focusing on clean-up over shut-down of coal plants and facilitating investments in battery storage technologies and cross-border electricity trade as RE and conventional fuel reach market parity

A review of challenges from increasing renewable generation in the Indian Power Sector: Way forward for Electricity (Amendment) Bill 2020

About 70% of India’s current energy mix comprises of coal, and the increase in generation from renewable (RE) sources is affecting the health of the power system. We investigated this effect through the lens of asset utilisation, cost and the social disruption caused by accelerating RE into the Indian Power System. Our review-driven analysis revealed that increasing RE generation is pushing the coal plants to operate in low-loading conditions, causing heightened wear and tear of the plant as they are not suitable for flexible operation. The novel analysis of social disruption due to market parity between RE and coal-based generation presented a holistic view of the political economy of Indian Power System. We found that transition from coal to RE may have extended socio-political ramifications that can potentially disrupt the national economy at an unprecedented scale. Policy implications outlined by our study for the draft Electricity (Amendment) Bill 2020 include scoping a socio-technical framework which supports just energy transition through better financial support mechanisms for flexible operation of coal plants. Focusing on clean-up over shut-down of coal plants and facilitating investments in battery storage technologies and cross-border electricity trade as RE and conventional fuel reach market parity. Bill and Melinda Gates Foundation [OPP1144] and Energy Transition Small Grant by Isaac Newton Trus

Density Evolution in the New Modified Chaplygin Gas Model

In this paper, we have considered new modified Chaplygin gas (NMCG) model which interpolates between radiation at early stage and $\Lambda$CDM at late stage. This model is regarded as a unification of dark energy and dark matter (with general form of matter). We have derived the density parameters from the equation of motion for the interaction between dark energy and dark matter. Also we have studied the evolution of the various components of density parameters.Comment: 6 Latex pages, 4 figures, RevTex styl

Origin of the anomalous magnetic circular dichroism spectral shape in ferromagnetic (Ga,Mn)As: Impurity bands inside the band gap

The electronic structure of a prototype dilute magnetic semiconductor (DMS), Ga1-xMnxAs, is studied by magnetic circular dichroism (MCD) spectroscopy. We prove that the optical transitions originated from impurity bands cause the strong positive MCD background. The MCD signal due to the E0 transition from the valence band to the conduction band is negative indicating that the p-d exchange interactions between the p-carriers and d-spin is antiferromagnetic. The negative E0 MCD signal also indicates that the hole-doping of the valence band is not so large as previously assumed. The impurity bands seem to play important roles for the ferromagnetism of Ga1-xMnxAs.Comment: 13 pages, 3 figure

Gravitational collapse due to dark matter and dark energy in the brane world scenario

Gravitational collapse of FRW brane world embedded in a conformaly flat bulk is considered for matter cloud consists of dark matter and dark energy with equation of state $p=\epsilon \rho$ $(\epsilon<-{1/3})$. The effect of dark matter and dark energy is being considered first separately and then a combination of them both with and without interaction. In some cases the collapse leads to black hole in some other cases naked singularity appears.Comment: 10 Latex Pages, RevTex style, 4 figure