Constraints on Lepton Asymmetry from Nucleosynthesis in a Linearly Coasting Cosmology

We study the effect of neutrino degeneracy on primordial nucleosynthesis in a universe in which the cosmological scale factor evolves linearly with time. The degeneracy parameter of electron type neutrinos ($\xi_e$) determines the $n/p$ (neutron to proton) ratio, which in turn determines the abundance of $^4$He in a manner quite distinct from the Standard Scenario. The observed abundances of $^4$He, $\mathrm{Y}_P$=0.254$\pm$0.003, and the minimum metallicity that is essential for fragmentation and cooling processes in star forming prestellar gas clouds (Z = Z$_{cr}$ = 10$^{-6}$Z$_\odot$), constrain the baryon to photon ratio, $\eta_B$=(3.927$\pm$0.292)10$^{-9}$, corresponding to a baryonic matter density, $\Omega_B$=0.263$\pm$ 0.026 and $\xi_e$=-2.165$\pm$0.171. This closes the dynamic mass estimates of matter in the universe by baryons alone. Useful byproducts are the threshold X(CNO) abundances required to trigger the CNO cycle in the observed low metallicity stars in the universe.Comment: 18 Pages, 9 Figures. Matches published versio

Coulomb screening in linear coasting nucleosynthesis

We investigate the impact of coulomb screening on primordial nucleosynthesis in a universe having scale factor that evolves linearly with time. Coulomb screening affects primordial nucleosynthesis via enhancement of thermonuclear reaction rates. This enhancement is determined by the solving Poisson equation within the context of mean field theory (under appropriate conditions during the primordial nucleosynthesis). Using these results, we claim that the mean field estimates of coulomb screening hardly affect the predicted element abundances and nucleosynthesis parameters$, \{\eta_9,\xi_e\}$. The deviations from mean field estimates are also studied in detail by boosting genuine screening results with the screening parameter ($\omega_s$). These deviations show negligible effect on the element abundances and on nucleosynthesis parameters. This work thus rules out the coulomb screening effects on primordial nucleosynthesis in slow evolving models and confirms that constraints in ref.[7] on nucleosynthesis parameters remain unaltered.Comment: 14 pages,11 figur

Engineering Phonon, Photon, Electron and Plasmon interactions in Silicon - Metal Nanocavitiies for Silicon Photonics and Thermoplasmonics

ENGINEERING PHONON, PHOTON, ELECTRON AND PLASMON INTERACTIONS IN SILICON - METAL NANOCAVITIIES FOR SILICON PHOTONICS AND THERMOPLASMONICS Daksh Agarwal Ritesh Agarwal, PhD Silicon photonics offers a cost effective solution to achieve ultrafast data processing speeds. But due to its indirect bandgap structure, making lasers from silicon is extremely difficult. Thus research has focused on nonlinear Raman processes in silicon as a method to achieve optical gain. Silicon nanowires provide an interesting platform for enhancing these nonlinearities because of their small size, geometry and relevant length scales. In the current work Raman measurements done on silicon nanowires reveal that up to twelvefold enhancement in Stokes scattering intensity and fourfold enhancement in anti Stokes scattering intensity can be attained depending on cavity structure and size, and excitation wavelength. In some cavities Stokes intensity depends on the sixth power of pump intensity, indicating extreme nonlinearity. Numerical calculations, done to understand the mechanism of these results indicate that silicon nanowires confine light to highly intense electric field modes inside the cavity which lead to stimulated Stokes and anti Stokes Raman scattering. Cavity modes can also be tuned to enhance the relative emission of either one of anti Stokes or Stokes photons which could enhance cavity cooling. These results would enable the development of smallest monolithically integratable silicon laser with extremely low lasing threshold and could lead to the development of next generation of high speed and energy efficient processors. The intense electric field inside the nanowire could also be used to enhance the degree of plasmon excitation in metallic nanoparticles. Silicon nanowires coated with a 10 nm thick gold film lead to strong plasmon excitation in gold and high cavity absorption which enable the cavity to heat up to temperatures of 1000K at relatively low pump powers. The cavities also give the ability to measure temperature attained during plasmon excitation and control the plasmon resonance wavelength. Because of the strong heating and plasmonic effects, these cavities show enhanced evolution rates of hydrogen, a crucial industrial building block and a promising fuel, in photoreforming reactions of alcohols

Development Cooperation Financing towards SDG7 and NDCs supporting energy system transition

In 2015, the adoption of the 2030 Agenda for Sustainable Development, including the 17 Sustainable Development Goals (SDGs), and the Paris Agreement provided a basis for considerable optimism for the fight against climate change and efforts to promote sustainable development, but their implementation remains an enormous challenge. Finance, in turn, plays a key role in implementation. This thesis thus seeks to provide new insights into the challenge of implementing the Paris Agreement and the 2030 Agenda by examining pertinent financial flows while taking into considering that making use of thematic overlaps between these two agendas can help to leverage synergies, especially if financial flows take adequate account of these overlaps. Since energy plays an essential role in both the goals of the Paris Agreement and the 2030 Agenda (in SDG 7 and beyond it), this thesis focuses on countries’ energy-related national commitments. Against this background, this thesis investigates the question which role energy plays in the Nationally Determined Contributions (NDCs) under the Paris Agreement and to what extent climate finance is considered in the context of the energy system transition. The key finding is that financial flow for renewable energy and energy efficiency improves globally with an unchanged track of non-renewable energy in the post-NDC period