Approximate Bayesian Computation for astronomical model analysis : a case study in galaxy demographics and morphological transformation at high redshift

Approximate Bayesian Computation’ (ABC) represents a powerful methodology for the analysis of complex stochastic systems for which the likelihood of the observed data under an arbitrary set of input parameters may be entirely intractable – the latter condition rendering useless the standard machinery of tractable likelihood-based, Bayesian statistical inference [e.g. conventional Markov chain Monte Carlo (MCMC) simulation]. In this paper, we demonstrate the potential of ABC for astronomical model analysis by application to a case study in the morphological transformation of high-redshift galaxies. To this end, we develop, first, a stochastic model for the competing processes of merging and secular evolution in the early Universe, and secondly, through an ABC-based comparison against the observed demographics of massive (Mgal > 1011 M⊙) galaxies (at 1.5 < z < 3) in the Cosmic Assembly Near-IR Deep Extragalatic Legacy Survey (CANDELS)/Extended Groth Strip (EGS) data set we derive posterior probability densities for the key parameters of this model. The ‘Sequential Monte Carlo’ implementation of ABC exhibited herein, featuring both a self-generating target sequence and self-refining MCMC kernel, is amongst the most efficient of contemporary approaches to this important statistical algorithm. We highlight as well through our chosen case study the value of careful summary statistic selection, and demonstrate two modern strategies for assessment and optimization in this regard. Ultimately, our ABC analysis of the high-redshift morphological mix returns tight constraints on the evolving merger rate in the early Universe and favours major merging (with disc survival or rapid reformation) over secular evolution as the mechanism most responsible for building up the first generation of bulges in early-type discs.

Forward slash story

FORWARD/STORY (Forward Slash Story) is an invite-only 3 day residential lab taking place May 16, 17 & 18th, 2014. A lab where storytellers working in tech don’t give presentations. There are no projects or mentors only peers. Participants share and explore the creative challenges of telling stories that break new ground. Five core challenges that storytellers face will be explored in a collaborative environment. On-site expenses are covered for those who attend. FORWARD/STORY attempts to tackle some of the most difficult problems surrounding storytelling in the 21st Century. A gathering of thinkers & doers working across a diversity of creative fields come together for 3 days focused on sharing, experimentation and innovation.

Starting with strengths : an Indigenous early years intervention

Aboriginal protocol usually links the right to tell a story with a declaration of involvement or connection to the story. I am Aboriginal . . . I am a woman, daughter, sister, aunty and wife. I am also a mother to three beautiful children aged 6, 4 and 2 years. To my children at this point in their lives, I am their provider, nurturer, teacher, cook, taxi driver, mediator, stylist, Elder, slave, and expert on all there is to know in the world. Being the centre of the universe to three impressionable young minds is a role that I cherish deeply, and I take the responsibilities of it very seriously. I love the job of parenting. As any parent would agree, it is the most challenging and difficult job of all, but the opportunity to bring a life into the world and shape and mould a little person into a big person brings rewards that no career can.

Developer charges and housing affordabilty in Brisbane, Australia

Purpose - This paper empirically examines the effect of developer charges on housing affordability in Brisbane, Australia. Developer paid fees or charges are a commonly used mechanism for local governments to pay for new urban infrastructure. Despite numerous government reports and many years of industry advocacy, there remains no empirical evidence in Australia to confirm or quantify passing on of these charges to home buyers. Design/methodology/approach - This research applies a hedonic house price model to 4,699 new and 25,053 existing house sales in Brisbane from 2005 to 2011. Findings – The findings of is research are consistent with international studies that support the proposition that developer charges are over passed. This study has provided evidence that suggest developer charges are over passed to both new and existing homes in the order of around 400%. Research limitations/implications - These findings suggest that developer charges are thus a significant contributor to increasing house prices and reduced housing affordability. Practical/Social Implications: By testing this effect on both new and existing homes, this research provides evidence in support of the proposition that not only are developer charges over passed to new home buyers but also to buyers of existing homes. Thus the price inflationary effect of these developer charges are being felt by all home buyers across the community, resulting in increased mortgage repayments of close to $1000 per month. Originality/value - This is the first study to empirically examine the impact of developer charges on house prices in Australia. These results are important as they will inform governments on the outcomes of growth management strategies on housing affordability, providing the first evidence of its kind in Australia.

Islamic fund and asset management: The opportunities and challenges of Islamic REITs

Purpose This paper aims to present a review on the issues and challenges for Islamic Funds and Asset Management, particularly the Islamic Real Estate Trusts (I-REITs) available in Malaysia. The key difference between the Islamic and the conventional investment vehicle is mainly the fund needs to adhere to the Shariah framework. Design/methodology/approach The paper reviews and synthesises the relevant literature on the framework of Islamic Asset and Fund Management, particularly the Islamic Real Estate Investment Trusts. The paper then provides insights for further research to address the issues and consider the Shariah framework applicable to other further research works. Findings The paper highlights the opportunities and challenges of Islamic REITs globally. There is a lack of the standardisation in the screening methodology used by the Malaysian I- REITs and Singapore I-REITs as the latter follows the Gulf Cooperation Council (GCC) guideline to capture the investors mainly from the Gulf countries. In term of tenants’ selection, there is similarity between I-REITs and the Socially Responsible Investment (SRI) or ethical investment. The gap between the investments can be bridged if the Islamic funds skewed the investment portfolio towards the social and ethical investment. Even though there is a limitation in the investment universe, I-REITs provide better diversification option and show better performance compared to the equity market during the economic crisis. The introduction of the Shariah-compliant REITs index for Asia Pacific allows the fund managers to benchmark the performance of either the funds or the sector with other investment vehicles. This will encourage more investors to consider I-REIT in the decision making of the asset allocation portfolio and broadening the horizon of the investment. Originality/value The contribution of the study is the examination and analysis of the Shariah framework currently adopted for Islamic REITs. This will assist in the identification of specific issues associated with Islamic REITs that will need to be addressed in the development and application of further research in the aspect of the management and operations to increase the efficiency level and better performance in order to capture more investors in this specific and promising market.

From the genius of man to the man of genius, part two: Inheriting (ideas about) genius

In Part One of ʻFrom the Genius of the Man to the Man of Geniusʼ I argued that classical and medieval inscriptions of genius figures suggest a coevalence between characters in their respective cosmologies, making it relatively more difficult to delineate Man from “spirits” and “other organisms”. The labour that genii performed flowed around two significant tropes of production and reproduction whose specificities were inflected in and across sources. In medieval poetry, for instance, genius figures took up a new role in regard to the reproduction trope, as promoter of virtue (in the form of censuring the seven deadly sins) and condemner of vice (in the form of prohibition against same sex intercourse). The sedimentation (complex processes of character-formation), directionality (patterns of descent) and sexual ecology (emergence of a field of ethics) that the medieval literature embodies also indexes an opening disarticulation of Man from universe and the possibility of grounding “morality” in and as His love choices. Through a series of narrative structures, binary concepts and new sources of authority under Christianity the figure now referred to in philosophy as “the subject” is given early grounds upon which to form in the medieval poems.

Submission to House of Representatives Standing Committee on Economics Inquiry into Home Ownership

This paper empirically examines the effect of current tax policy on home ownership, specifically looking at how developer contributions impact house prices. Developer contributions are a commonly used mechanism for local governments to pay for new urban infrastructure. This research applies a hedonic house price model to 4,699 new and 25,053 existing house sales in Brisbane from 2005 to 2011. The findings of is research are consistent with international studies that support the proposition that developer contributions are over passed. This study has provided evidence that suggest developer contributions are over passed to both new and existing homes in the order of around 400%. These findings suggest that developer contributions are thus a significant contributor to increasing house prices, reduced housing supply and are thus an inefficient and inequitable tax. By testing this effect on both new and existing homes, this research provides evidence in support of the proposition that not only are developer contributions over passed to new home buyers but also to buyers of existing homes. Thus the price inflationary effect of these developer contributions are being felt by all home buyers across the community, resulting in increased mortgage repayments of close to $1,000 per month in Australia. This is the first study to empirically examine the impact of developer contributions on house prices in Australia. These results are important as they inform governments on the outcomes of current tax policy on home ownership, providing the first evidence of its kind in Australia. This is an important contribution to the tax reform agenda in Australia.

Bayesian model comparison in cosmology with Population Monte Carlo

We use Bayesian model selection techniques to test extensions of the standard flat LambdaCDM paradigm. Dark-energy and curvature scenarios, and primordial perturbation models are considered. To that end, we calculate the Bayesian evidence in favour of each model using Population Monte Carlo (PMC), a new adaptive sampling technique which was recently applied in a cosmological context. The Bayesian evidence is immediately available from the PMC sample used for parameter estimation without further computational effort, and it comes with an associated error evaluation. Besides, it provides an unbiased estimator of the evidence after any fixed number of iterations and it is naturally parallelizable, in contrast with MCMC and nested sampling methods. By comparison with analytical predictions for simulated data, we show that our results obtained with PMC are reliable and robust. The variability in the evidence evaluation and the stability for various cases are estimated both from simulations and from data. For the cases we consider, the log-evidence is calculated with a precision of better than 0.08. Using a combined set of recent CMB, SNIa and BAO data, we find inconclusive evidence between flat LambdaCDM and simple dark-energy models. A curved Universe is moderately to strongly disfavoured with respect to a flat cosmology. Using physically well-motivated priors within the slow-roll approximation of inflation, we find a weak preference for a running spectral index. A Harrison-Zel'dovich spectrum is weakly disfavoured. With the current data, tensor modes are not detected; the large prior volume on the tensor-to-scalar ratio r results in moderate evidence in favour of r=0.