Relativistic models of the universe with pressure equal to zero and time-dependent uniformity

Zero density and approximate, relativistic models of univers

Did Neoliberalizing West African Forests Produce a New Niche for Ebola?

A recent study introduced a vaccine that controls Ebola Makona, the Zaire ebolavirus variant that has infected 28,000 people in West Africa. We propose that even such successful advances are insufficient for many emergent diseases. We review work hypothesizing that Makona, phenotypically similar to much smaller outbreaks, emerged out of shifts in land use brought about by neoliberal economics. The epidemiological consequences demand a new science that explicitly addresses the foundational processes underlying multispecies health, including the deep-time histories, cultural infrastructure, and global economic geographies driving disease emergence. The approach, for instance, reverses the standard public health practice of segregating emergency responses and the structural context from which outbreaks originate. In Ebola's case, regional neoliberalism may affix the stochastic "friction" of ecological relationships imposed by the forest across populations, which, when above a threshold, keeps the virus from lining up transmission above replacement. Export-led logging, mining, and intensive agriculture may depress such functional noise, permitting novel spillovers larger forces of infection. Mature outbreaks, meanwhile, can continue to circulate even in the face of efficient vaccines. More research on these integral explanations is required, but the narrow albeit welcome success of the vaccine may be used to limit support of such a program.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Photometric Determination of Main-Sequence Binaries with Gaia

Since its launch in 2013, the Gaia space telescope has provided precise measurements of the positions and magnitudes of over 1 billion stars. This has enabled extensive searches for stellar and sub-stellar companions through astrometric and radial velocity measurements. However, these surveys require a prior knowledge of any unresolved companion affecting the results which can be identified using photometry. In this work, Gaia's magnitude measurements are combined with near-infrared observations from 2MASS and WISE and simulation-based inference is applied to constrain astrophysical parameters and search for hidden companions. This method is first tested on simulated sets of binary stars before expanding to Gaia's non-single star catalogue. Using this test, a region is identified on the H-R diagram in which the method is the most accurate and all Gaia sources within that region are analysed. This analysis reproduces a known anti-correlation between metallicity and binary fraction. Finally, the method is applied to the nearby star cluster M67 and, using previous studies of the metallicity distribution, it is possible to improve constraints on binary fraction. From this the binary fraction in the cluster is calculated to vary from 30% in the outer cluster to 45% near the core. This is found to be significantly higher the 23% binary fraction calculated for the wider stellar neighbourhood.Comment: 10 pages, 15 figures, accepted for publication by MNRA