224 research outputs found
Planck data versus large scale structure:Methods to quantify discordance
No full textDiscordance in the Λ cold dark matter cosmological model can be seen by comparing parameters constrained by cosmic microwave background (CMB) measurements to those inferred by probes of large scale structure. Recent improvements in observations, including final data releases from both Planck and SDSS-III BOSS, as well as improved astrophysical uncertainty analysis of CFHTLenS, allows for an update in the quantification of any tension between large and small scales. This paper is intended, primarily, as a discussion on the quantifications of discordance when comparing the parameter constraints of a model when given two different data sets. We consider Kullback-Leibler divergence, comparison of Bayesian evidences and other statistics which are sensitive to the mean, variance and shape of the distributions. However, as a byproduct, we present an update to the similar analysis in [R. A. Battye, T. Charnock, and A. Moss, Phys. Rev. D 91, 103508 (2015)PRVDAQ1550-799810.1103/PhysRevD.91.103508], where we find that, considering new data and treatment of priors, the constraints from the CMB and from a combination of large scale structure (LSS) probes are in greater agreement and any tension only persists to a minor degree. In particular, we find the parameter constraints from the combination of LSS probes which are most discrepant with the Planck2015+Pol+BAO parameter distributions can be quantified at a ∼2.55σ tension using the method introduced in [R. A. Battye, T. Charnock, and A. Moss, Phys. Rev. D 91, 103508 (2015)PRVDAQ1550-799810.1103/PhysRevD.91.103508]. If instead we use the distributions constrained by the combination of LSS probes which are in greatest agreement with those from Planck2015+Pol+BAO this tension is only 0.76σ.</p
Removing beam asymmetry bias in precision cmb temperature and polarization experiments
No full textAsymmetric beams can create significant bias in estimates of the power spectra from CMB experiments. With the temperature power spectrum many orders of magnitude stronger than the B-mode power spectrum any systematic error that couples the two must be carefully controlled and/or removed. Here, we derive unbiased estimators for the CMB temperature and polarisation power spectra taking into account general beams and general scan strategies. A simple consequence of asymmetric beams is that, even with an ideal scan strategy where every sky pixel is seen at every orientation, there will be residual coupling from temperature power to B-mode power if the orientation of the beam asymmetry is not aligned with the orientation of the co-polarisation. We test our correction algorithm on simulations of two temperature-only experiments and demonstrate that it is unbiased. The simulated experiments use realistic scan strategies, noise levels and highly asymmetric beams. We also develop a map-making algorithm that is capable of removing beam asymmetry bias at the map level. We demonstrate its implementation using simulations and show that it is capable of accurately correcting both temperature and polarisation maps for all of the effects of beam asymmetry including the effects of temperature to polarisation leakage
Future Science Prospects for AMI
No full textAuthors:- Keith Grainge, Paul Alexander, Richard Battye, Mark Birkinshaw, Andrew Blain, Malcolm Bremer, Sarah Bridle, Michael Brown, Richard Davis, Clive Dickinson, Alastair Edge, George Efstathiou, Robert Fender, Martin Hardcastle, Jennifer Hatchell, Michael Hobson, Matthew Jarvis, Benjamin Maughan, Ian McHardy, Matthew Middleton, Anthony Lasenby, Richard Saunders, Giorgio Savini, Anna Scaife, Graham Smith, Mark Thompson, Glenn White, Kris Zarb-Adami, James Allison, Jane Buckle, Alberto Castro-Tirado, Maria Chernyakova, Roger Deane, Farhan Feroz, Ricardo Genova Santos, David Green, Diana Hannikainen, Ian Heywood, Natasha Hurley-Walker, Ruediger Kneissl, Karri Koljonen, Shrinivas Kulkarni, Sera Markoff, Carrie MacTavish, Michael McCollough, Simone Migliari, Jon M. Miller, James Miller-Jones, Malak Olamaie, Zsolt Paragi, Timothy Pearson, Guy Pooley, Katja Pottschmidt, Rafael Rebolo, John Richer, Julia Riley, Jerome Rodriguez, Carmen Rodriguez-Gonzalvez, Anthony Rushton, Petri Savolainen, Paul Scott, Timothy Shimwell, Marco Tavani, John Tomsick, Valeriu Tudose, Kurt van der Heyden, Alexander van der Horst, Angelo Varlotta, Elizabeth Waldram, Joern Wilms, Andrzej Zdziarski, Jonathan Zwart, Yvette Perrott, Clare Rumsey, Michel SchammelThe Arcminute Microkelvin Imager (AMI) is a telescope specifically designed for high sensitivity measurements of low-surface-brightness features at cm-wavelength and has unique, important capabilities. It consists of two interferometer arrays operating over 13.5-18 GHz that image structures on scales of 0.5-10 arcmin with very low systematics. The Small Array (AMI-SA; ten 3.7-m antennas) couples very well to Sunyaev-Zel'dovich features from galaxy clusters and to many Galactic features. The Large Array (AMI-LA; eight 13-m antennas) has a collecting area ten times that of the AMI-SA and longer baselines, crucially allowing the removal of the effects of confusing radio point sources from regions of low surface-brightness, extended emission. Moreover AMI provides fast, deep object surveying and allows monitoring of large numbers of objects. In this White Paper we review the new science - both Galactic and extragalactic - already achieved with AMI and outline the prospects for much more.https://arxiv.org/abs/1208.196
Spinning Skyrmions and the Skyrme parameters
No full textThe traditional approach to fixing the parameters of the Skyrme model requires the energy of a spinning Skyrmion to reproduce the nucleon and delta masses. The standard Skyrme parameters, which are used almost exclusively, fix the pion mass to its experimental value and fit the two remaining Skyrme parameters by approximating the spinning Skyrmion as a rigid body. In this paper we remove the rigid body approximation and perform numerical calculations which allow the spinning Skyrmion to deform and break spherical symmetry. The results show that if the pion mass is set to its experimental value then the nucleon and delta masses can not be reproduced for any values of the Skyrme parameters; the commonly used Skyrme parameters are simply an artifact of the rigid body approximation. However, if the pion mass is taken to be substantially larger than its experimental value then the nucleon and delta masses can be reproduced. This result has a significant effect on the structure of multi-Skyrmions
Sovereign voices
No full textWhat are the pivotal factors underlying the development and viability of regional Indigenous organisations committed to preserving and promulgating the cultural knowledge of their people? This question is investigated in the experience of Roebourne-based Juluwarlu Group Aboriginal Corporation from 2002-08 as it grew from a small scale, subsistence-funded, cultural recording organisation, into an archiving, publishing, digital media, television broadcasting, media training, cultural consultancy, advocacy and Native Title management enterprise.
This study pays careful attention to post-World War II Pilbara history which featured the creation of the Roebourne Aboriginal ghetto and the mining boom that overwhelmed the region in the 1960s and 70s, and more recently was marked by Native Title, the conservative Howard Government, post-ATSIC administrative/ political climate, and the resurgence in iron ore and gas stocks. Also examined are the effects, both on cultural practice in Roebourne and Juluwarlu’s development, of the documentary Exile and The Kingdom, which was produced with the community by the author and Noelene Harrison between 1987 and 1993.1 These histories inform both the reasons for Juluwarlu’s emergence and the meaning of its achievements.
Key findings converge on the character and consequence of leadership and the generative efficacy of the Yindjibarndi cultural, social and ethical system; the advantage obtained via considered partnerships with collaborators; and the adaptive engagement of Indigenous tradition with management principles and communications and media technology – on Indigenous terms, rather than the labour-market-driven schemes that, for example, seek to match Indigenous disadvantage or development with labour shortages in the Pilbara resources industries.
This thesis diverges from other studies that have typically researched Indigenous disadvantage within the context of broader public policy/legislation and political economy, albeit these contexts inevitably inform it. Instead, primary attention is given to the experimental and generative capacity that Juluwarlu brought to negotiating advantage from public and private institutions, challenging their recalcitrance, and sometimes moving beyond them. Finally, Sovereign Voices records how Juluwarlu’s responsibility for country and culture, and insistence on respect and equitable acknowledgement for their custodianship, was charged by media and communications technologies, and how these in turn ramified its organisational wherewithal for the benefit of their community – both practically and a symbolically. Juluwarlu’s mediation and giving of voice, I contend, militated against the ‘silencing’ shroud of the corporate-state-media hegemony
“Film Censorship in Western Australia: Public, Government and Industrial Responses 1898-1928”
No full textMuch work has been undertaken by legal writers on the present debates surrounding censorship in Australia.Many of these writings focus their critique on the extent to which Australian censorship law attempts to regulate public morality and the problems that arise form such an approach. Other work has critiqued the issue of whether this legislative sphere is best handled at the Federal level or the State level. While this work is important in its own right, very little of this work describes the historical debates and reform initiatives from which present legislative censorship policies now find their source. This leaves an unfortunate gap in the writing on state sanctioned censorship within this country, for without an understanding of the ways in which the public and past governments have responded to calls for tighter controls on what people should view, an incomplete understanding of the source and reasons for modern day censorship campaigns emerges.
This paper examines the responses made by the Western Australian public, government and film industry to the question of film censorship between 1898 and 1928: it examines the similarities and differences between Western Australian responses and responses in the eastern states. It aims to rectify two major imbalances in existing work: firstly, the stress upon eastern states' responses as representative of Australia as a whole; and secondly, the failure to integrate political, social and economic influences which shaped the development of film censorship. As well it identifies transitions in public perceptions of film between 1898 and 1928.
While there were similarities in Western Australia and eastern states' responses to film there were also differences, particularly in the way government and public organisations responded to the debate. In particular, the conclusion drawn in previous studies, that the public initially complained about film as medium rather than film's message is not true for Western Australia. As well, there were noticeable transitions in the way people perceived the effects of film. In the 1910s organisations did not complain about both the immorality of film content and the link between film and criminal behaviour. Rather the debate about criminal behaviour did not develop until after 1916 and this transition was a reflection of the changing content of film in this period. An examination of political, social and economic factors affecting film censorship in Western Australia indicates that an analysis of film censorship which ignores any of these factors within their historical context ignores the complex interplay which shaped Australian film censorship controls and which arguably impact upon present day censorship policies.
This paper is divided into five parts. Part One discusses the introduction of moving pictures into Western Australia and highlights some misconceptions which have occurred in previous studies of this early period. Parts Two and Three examine government, industrial and public responses to the question of film censorship between 1911 and 1927. Part four discusses the Minutes of Evidence from the Royal Commission and Part five provides the conclusion. Central to the paper is the changing public perceptions, between the early 1900s and 1927, of the effect of films upon the child and society
What is vital force? or, A short and comprehensive sketch, including vital physics, animal morphology, and epidemics; to which is added an appendix upon geology: Is the detrital theory of geology tenable?
No full textNeutral hydrogen surveys for high redshift galaxy clusters and proto-clusters
No full textWe discuss the possibility of performing blind surveys to detect large-scale features of the Universe using 21-cm emission. Using instruments with ∼5–10 arcmin resolution currently in the planning stage, it should be possible to detect virialized galaxy clusters at intermediate redshifts using the combined emission from their constituent galaxies, as well as less overdense structures, such as protoclusters and the ‘cosmic web’, at higher redshifts. Using semi-analytic methods, we compute the number of virialized objects and those at turnaround which might be detected by such surveys. We find that there is a surprisingly large number of objects even using small (∼5 per cent) bandwidths and elaborate on some issues pertinent to optimizing the design of the instrument and the survey strategy. The main uncertainty is the fraction of neutral gas relative to the total dark matter within the object. We discuss this issue in the context of the observations which are currently available
Generic junction conditions in brane-world scenarios
No full textWe present the generic junction conditions obeyed by a co-dimension one brane in an arbitrary background space-time. As well as the usual Darmois-Israel junction conditions which relate the discontinuity in the extrinsic curvature to the energy-momentum tensor of matter which is localized to the brane, we point out that another condition must also be obeyed. This condition, which is the analogous to Newton's second law for a point particle, is trivially satisfied when Z2 symmetry is enforced by hand, but in more general circumstances governs the evolution of the brane world-volume. As an illustration of its effect we compute the force on the brane due to a form field. © 2001 Elsevier Science B.V
Dark energy and large scale structure
No full textCurrently one of the most exciting problems in cosmology is the nature of dark energy, which is responsible for the late time accelerated expansion of the universe. Dark energy modifies the distance-redshift relation, and governs the late time evolution of gravitational potentials in the universe. Therefore by observing large scale structure we can gain valuable information on the nature of dark energy. In this thesis we examine a particular theory of dark energy, known as elastic dark energy. Using weak lensing and the ISW effect, coupled with CMB and SNIa data, we find lower bounds for the sound speed of elastic dark energy. We also explore how this model behaves in the presence of collapsing matter.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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