Type V singularities with inhomogeneous equations of state

Interest in cosmological singularities has remarkably grown in recent times, particularly on future singularities with the discovery of late-time acceleration of the universe and dark energy. Recent work has seen a proper classification of such singularities into strong and weak based on their strength, with weak singularities being the likes of sudden, w and big freeze singularities and strong singularities like the big rip. This has led to a classification of such singularities in various types like Big rip is Type 1, w-singularity is type V etc. While singularities of type I-type IV have been discussed vividly by taking into account inhomogeneous equations of state (EOS), the same has not been attempted for type V singularities. So in this work we have discussed in detail about the formation of type V singularities in various cosmologies after considering inhomogeneous equations of state. We consider two inhomogeneous forms of the EOS in the context of four different cosmological backgrounds ; standard general relativistic cosmology, an asymptotically safe cosmology, a cosmology inspired by modified area-entropy relations, generalized uncertainty principles, holographic renormalization and Chern-Simons gravity( all of which can be coincidentally described by the same form of the modified Friedmann equation) and an f(R) gravity cosmology. We show in detail that one sees some very big differences in the occurence conditions of type V singularities when one makes such considerations. In the particular case of the f(R) gravity cosmology, we see that the type V singularities get completely removed. This work goes to show that the creation and formation of type V singularities is influenced most strongly by the form of the equation of state that one considers, way more so than what background cosmology one chooses.Comment: v2 , 20 pages with some references added, matches the published version in PL

Bypassing the selection rule in choosing controls for a case-control study

Objectives It has been argued that in case–control studies, controls should be drawn from the base population that gives rise to the cases. In designing a study of occupational injury and risks arising from long-term illness and prescribed medication, we lacked data on subjects' occupation, without which employed cases (typically in manual occupations) would be compared with controls from the general population, including the unemployed and a higher proportion of white-collar professions. Collecting the missing data on occupation would be costly. We estimated the potential for bias if the selection rule were ignored. Methods: We obtained published estimates of the frequencies of several exposures of interest (diabetes, mental health problems, asthma, coronary heart disease) in the general population, and of the relative risks of these diseases in unemployed versus employed individuals and in manual versus non-manual occupations. From these we computed the degree of over- or underestimation of exposure frequencies and exposure ORs if controls were selected from the general population. Results: The potential bias in the OR was estimated as likely to fall between an underestimation of 14% and an overestimation of 36.7% (95th centiles). In fewer than 6% of simulations did the error exceed 30%, and in none did it reach 50%. Conclusions: For the purposes of this study, in which we were interested only in substantial increases in risk, the potential for selection bias was judged acceptable. The rule that controls should come from the same base population as cases can justifiably be broken, at least in some circumstances. <br/

Rejuvenating the hope of a swampland consistent inflated multiverse with tachyonic inflation in the high energy RS-II Braneworld

The swampland conjectures from string theory have had some really interesting implications on cosmology, in particular on inflationary models. Some models of inflation have been shown to be incompatible with these criterion while some have been shown to be severely fine tuned, with most of these problems arising in single field inflationary models in a General relativistic cosmology. Recent works have although optimistically shown that single field models in more general cosmologies can be consistent with these conjectures and hence there is an optimism that not all such models lie in the swampland. However a paradigm of inflation which has been shown to not be perfectly okay with the conjectures is eternal inflation. So in this work, we discuss Tachyonic inflation in the high energy RS-II Braneworld scenario in the context of the swampland conjectures while also considering the possibility of swampland consistent eternal inflation. We show that our concerned regime evades all the prominent swampland issues for single field inflation being virtually unscathed. After this, we show that the main conflicts of eternal inflation with the swampland can easily be resolved in the considered tachyonic scenario and in particular, we also discuss the exciting prospect of a Generalized Uncertainty Principle facilitating the notion of Swampland consistent eternal inflation. Our work as a whole reignites the possibility that there can be a swampland (and possibly, quantum gravitationally) consistent picture of a "Multiverse".Comment: v2, 22 pages with some changes, matches the published version in MPL

Accelerating phytoplankton phenomics through FTIR spectroscopy

University of Technology Sydney. Faculty of Science.Marine phytoplankton play a driving role in global biogeochemical cycling, providing fuel for marine and terrestrial ecosystems, and removing substantial quantities of CO₂ from the atmosphere. Phytoplankton respond to environmental change by varying their phenotypes, including photophysiology, macromolecular composition and morphology. Southern Ocean phytoplankton are subjected to one of the most extreme habitats on earth, resulting in great phenotypic variation between and within taxonomic groups. Given they provide a significant net sink of atmospheric CO₂ and support the most biologically productive ecosystem on earth, improving our ability to predict the responses of Southern Ocean phytoplankton to environmental change is of global importance. At present, our ability to predict the responses of these critical organisms to environmental change, including climate change, is limited by a bottleneck in the efficiency with which we can characterise phytoplankton phenotypes. This thesis demonstrates the feasibility of accelerating phytoplankton phenomics using Fourier Transform Infrared (FTIR) microspectroscopy, a powerful yet under-utilised frontier technology. The extensive phenotypic variation shown by Southern Ocean phytoplankton provided excellent scope for demonstrating the power of the microspectroscopic approach. Coupling the microspectroscopic approach with multivariate modeling tools enabled the characterisation of phenotypic plasticity from cell FTIR spectra. When combined with mass spectrometry data, cell FTIR spectra provided accurate estimates of multiple phenotypic parameters including cellular protein, carbon and energy. Of particular value, spectroscopic models were able to accurately estimate rates of carbon production from samples taken at a single time-point, circumventing the need to take measurements over time. Further, the high spatial resolution achievable with microspectroscopy enabled the analysis of individual cells, revealing taxon-specific responses to iron availability within samples taken from a mixed natural Southern Ocean phytoplankton bloom. This work demonstrates that incorporating FTIR microspectroscopy into the phenomics toolbox will improve the efficiency of phenotypic data collection and, in combination with multivariate modeling, will enable the development of powerful, taxon-specific predictive phenomic models

Implications of single field inflation in general cosmological scenarios on the nature of dark energy given the swampland conjectures

Swampland Conjectures have attracted quite some interest in the Cosmological Community. They have been shown to have wide ranging implications , like Constraints on Inflationary Models, Primordial Black Holes etc. to name a few. A particularly revealing insight on dark energy also shows that one can have the dark energy equation of state for a quintessence scenario to be signficantly different than -1 after one takes into account the refined dS conjecture. Another interesting issue with the swampland conjectures is that they have been shown to be incompatible with single field inflationary models in GR based cosmology. In our previous work we have, however, showed that single field inflationary models are quite compatible with swampland conjectures in their usual string theoretic form in a large class of modified cosmological scenarios. Building on that work, we now show that in modified cosmological scenarios where the early universe expansion was driven by single field inflation , one can have the dark energy equation of state to be significantly different from -1 even if we just take into account the original dS conjecture, let alone the refined form of that. We thereby show that one does not need to apply a step function approach towards inflation in order to have an observable distinction between constant and non constant dark energy models in the context of the swampland conjectures.Comment: v2, 9 pages long with added references and minor detail