An exposition on Friedmann Cosmology with Negative Energy Densities

How would negative energy density affect a classic Friedmann cosmology? Although never measured and possibly unphysical, certain realizations of quantum field theories leaves the door open for such a possibility. In this paper we analyze the evolution of a universe comprising varying amounts of negative energy forms. Negative energy components have negative normalized energy densities, $\Omega < 0$. They include negative phantom energy with an equation of state parameter $w<-1$, negative cosmological constant: $w=-1$, negative domain walls: $w=-2/3$, negative cosmic strings: $w=-1/3$, negative mass: $w=0$, negative radiation: $w=1/3$ and negative ultralight: $w > 1/3$. Assuming that such energy forms generate pressure like perfect fluids, the attractive or repulsive nature of negative energy components are reviewed. The Friedmann equation is satisfied only when negative energy forms are coupled to a greater magnitude of positive energy forms or positive curvature. We show that the solutions exhibit cyclic evolution with bounces and turnovers.The future and fate of such universes in terms of curvature, temperature, acceleration, and energy density are reviewed. The end states are dubbed Big Crunch, Big Void, or Big Rip and further qualified as "Warped", "Curved", or "Flat", "Hot" versus "Cold", "Accelerating" versus "Decelerating" versus "Coasting". A universe that ends by contracting to zero energy density is termed "Big Poof." Which contracting universes "bounce" in expansion and which expanding universes "turnover" into contraction are also reviewed.Comment: Abridged version with minor correction

[O II] nebular emission from Mg II absorbers: Star formation associated with the absorbing gas

We present nebular emission associated with 198 strong Mg II absorbers at 0.35 $\le z \le$ 1.1 in the fibre spectra of quasars from the Sloan Digital Sky Survey. Measured [O II] luminosities (L$_{[O II]}$) are typical of sub-L$^{\star}$ galaxies with derived star formation rate (uncorrected for fibre losses and dust reddening) in the range of 0.5-20 ${\rm M_\odot\ yr^{-1}}$. Typically less than$\sim$3equivalent width,$W_{2796}$$\ge$2 \AA, show L$_{[O II]} \ge 0.3$L$^{\star}_{[O II]}$. The detection rate is found to increase with increasing$W_{2796}$and$z$. No significant correlation is found between$W_{2796}$and L$_{[O II]}$even when we restrict the samples to narrow$z$-ranges. A strong correlation is seen between L$_{[O II]}$and$z$. While this is expected from the luminosity evolution of galaxies, we show finite fibre size plays a very crucial role in this correlation. The measured nebular line ratios (like [O III]/[O II] and [O III]/H$\beta$) and their$z$evolution are consistent with those of galaxies detected in deep surveys. Based on the median stacked spectra, we infer the average metallicity (log Z$\sim$8.3), ionization parameter (log$q$$\sim$7.5) and stellar mass (log (M/M$_\odot$)$\sim$9.3). The Mg II systems with nebular emission typically have$W_{2796}$$\ge 2$\AA, Mg II doublet ratio close to 1 and W(Fe II$\lambda$2600)/$W_{2796}$$\sim 0.5$as often seen in damped Ly$\alpha$and 21-cm absorbers at these redshifts. This is the biggest reported sample of [O II] emission from Mg II absorbers at low impact parameters ideally suited for probing various feedback processes at play in$z\le 1$ galaxies.Comment: 18 Pages, 18 Figures, 4 Tables (Accepted for the Publication in MNRAS main-journal

Crosslinked conventional size and nanoparticle size acrylic latexes and their blends: Investigation of the effects of crosslinking, particle size and distribution, glass transition temperature and blending on film formation, properties and morphology

Synthetic latexes have many product applications including functioning as a binder in paints and coatings. For many years, researchers in industry as well as in academe have been exploring various strategies to improve performance of acrylic latexes mainly to replace traditionally used solvent borne coatings due to increasing environmental concerns and strict governmental regulations. The main goal of the study is to investigate the effects of type (pre-coalescence or post-coalescence) and level of crosslinking, particle size (nano particle size ~ 20-25 nm vs. conventional particle size ~ 120-130 nm) and distribution, glass transition temperature (Tg), and blending on latex film formation process, properties and latex morphology. Films cast from these latexes were characterized using specific end use tests and fundamental properties using advanced instruments such as a dynamic mechanical analyzer (DMA), thermogravimetric analyzer (TGA), modulated differential scanning calorimeter (MDSC), nano-indenter, and atomic force microscope (AFM). The results showed significant improvements in acrylic latex performance proposing coatings near zero VOC and forming basis for exploring potential commercial applications of functional nanosize latexes and their blends