Challenges to Self-Acceleration in Modified Gravity from Gravitational Waves and Large-Scale Structure

With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realized. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar-tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3-sigma poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar-tensor modification of gravity.Comment: 5 pages; v2 updated with newer data; v3 extended titl

Reconstructing thawing quintessence with multiple datasets

In this work we model the quintessence potential in a Taylor series expansion, up to second order, around the present-day value of the scalar field. The field is evolved in a thawing regime assuming zero initial velocity. We use the latest data from the Planck satellite, baryonic acoustic oscillations observations from the Sloan Digital Sky Survey, and Supernovae luminosity distance information from Union2.1 to constrain our models parameters, and also include perturbation growth data from the WiggleZ, BOSS and the 6dF surveys. The supernova data provide the strongest individual constraint on the potential parameters. We show that the growth data performance is competitive with the other datasets in constraining the dark energy parameters we introduce. We also conclude that the combined constraints we obtain for our model parameters, when compared to previous works of nearly a decade ago, have shown only modest improvement, even with new growth of structure data added to previously-existent types of data.Comment: 9 pages, 4 figures and 1 table. Version 2 with minor changes to match Physical Review D accepted versio

Rapid isolation and identification of fungi from bottled water production system

Analyses of fungi by conventional methods are time consuming. At least two weeks are required for growth and identification of even the most rapidly growing fungi. Where initial contamination levels may be very low as in bottled water, it is difficult to obtain representative samples using traditional sampling and isolation techniques. The major problem report by bottlers is the failure to detect contaminations during routine quality control analysis. The fungi manifests in the bottles when the product has reached the retailer, exactly the point of maximum exposure to the consumer. One way to avoid these problems is to decrease the time of fungal incubation using modified media. In order to adapt the existing mycological media, Penicillium brevicompactum was used to spike bottled water. The recovery of viable fungal was determined. Modifications in strength of Neopeptone Glucose Rose Bengal Aureomycin Agar were assessed. The fluorescent dyes (e.g. calcofluor white) and other substrates for specific enzymatic activities were also used as potentially diagnostic supplements.EU project QLK1-CT-2002-7084