QSO clustering and the AAT 2dF redshift survey

We review previous results on the clustering and environments of QSOs. We show that the correlation length for QSOs derived from existing surveys is r~5/h Mpc, similar to the observed correlation length for field galaxies at the present epoch. The galaxy environment for z<1 radio-quiet QSOs is also consistent with field galaxies. The evolution of the QSO correlation length with redshift is currently uncertain, largely due to the small numbers of QSOs (~2000) in surveys suitable for clustering analysis. We report on intial progress with the AAT 2dF QSO redshift survey, which, once completed will comprise almost 30000 QSOs. With over 1000 QSOs already observed, it is already the largest single homogeneous QSO survey. We discuss prospects for deriving limits on cosmological parameters from this survey, and on the evolution of large-scale structure in the Universe.Comment: Invited talk at RS meeting on 'Large Scale Structure in the Universe' held at the Royal Society on 25-26 March 1998 14 pages, 11 figre

Probing the Evolution of the Galaxy Interaction/Merger Rate Using Collisional Ring Galaxies

We present the results from our program to determine the evolution of the galaxy interaction/merger rate with redshift using the unique star-forming characteristics of collisional ring galaxies. We have identified 25 distant collisional ring galaxy candidates (CRGCs) in a total of 162 deep Hubble Space Telescope Wide Field/Planetary Camera-2 images obtained from the HST Archives. Based on measured and estimated redshifts, these 25 CRGCs all lie in the redshift interval of 0.1 < z < 1. Using the local collisional ring galaxy volume density and the new ``standard'' cosmology, we find that in order to account for the number of identified CRGCs in our surveyed fields, the galaxy interaction/merger rate, parameterized as (1 + z)^m, must increase steeply with redshift.We determine a minimum value of m = 5.2 $\pm$ 0.7, though m could be as high as 7 or 8. We can rule out a non-evolving (m = 0) and weakly evolving (m = 1-2) galaxy interaction/merger rate at greater than the 4 sigma level of confidence.Comment: Accepted in the Astrophysical Journal (11 pages, 4 figures). Higher resolution version of the figures is available at http://www.astro.cornell.edu/~vassilis/papers

Fine tuning and the ratio of tensor to scalar density fluctuations from cosmological inflation

The form of the inflationary potential is severely restricted if one requires that it be natural in the technical sense, i.e. terms of unrelated origin are not required to be correlated. We determine the constraints on observables that are implied in such natural inflationary models, in particular on $r$, the ratio of tensor to scalar perturbations. We find that the naturalness constraint does not require $r$ to be lare enough to be detectable by the forthcoming searches for B-mode polarisation in CMB maps. We show also that the value of $r$ is a sensitive discriminator between inflationary models.Comment: 8 pages LaTeX; clarifications and a reference added; to appear in JCA

Status Report on the Hydrodynamic Simulations of a Tapered Plasma Lens for Optical Matching at the ILC e+e^+ Source

The International Linear Collider is a planned electron-positron linear collider with its positron source producing positrons by aiming undulator radiation onto a rotating target. The resulting, highly divergent positron beam requires immediate optical matching to improve the luminosity and therefore the success of the intended collision experiments. Here, optical matching refers to the process of capturing particles and making them available for downstream beamline elements like accelerators. In the past, this has been done with sophisticated coils, but more recently the usage of a current-carrying plasma, a so-called plasma lens, has been proposed as an alternative. For the International Linear Collider idealised particle tracking simulations have already been done with the purpose of finding the optimal plasma lens design with respect to the captured positron yield. The proposed design is characterised by a linearly widened radius in beam direction. Now further research and development of this design is required, including both experiments with a prototype set-up as well as corresponding simulations modelling the hydrodynamics of the current-carrying plasma and the resulting magnetic field. The accuracy of the latter will benefit greatly from the former. In this work, first preliminary hydrodynamic simulations instil confidence into further endeavours.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS 2023), 15-19 May 2023. C23-05-15.

Pion mass dependence of the Kl3K_{l3} semileptonic scalar form factor within finite volume

We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer $t_{m} = (m_{K} - m_{\pi})^2$, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then evaluate the finite size effects for two volumes with $L = 1.83 fm$ and $L= 2.73 fm$ and find that the difference between the finite volume corrections of the two volumes are larger than the difference as quoted in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper can be useful for Lattice data to extrapolate at large lattice size.Comment: 19 pages, 5 figures, accepted for publication in EPJ

Relationship between pig carcass tail lesions and lung lesions

Tail biting is common on farms that are more prone to disease. Tail lesions can be associated with poor health either directly by providing a route of entry for pathogens or indirectly as conditions which trigger tail biting may also affect pig health. The aim of this study was to investigate the relationship between carcass tail lesion and lung lesion severity scores in Irish slaughter pigs. Factory visits occurred over 5 days (Jan – March 2015) and tail lesion score (0 – 4) according to severity, sex, and kill number was recorded for every pig after scalding and dehairing. The lungs from each carcass were scored for lesions using an adapted version of the BPEX pig health scheme. Presence of pleuropneumonia (APP), abscesses and pyaemia was recorded. The severity of enzootic pneumonia (EP-like lesions) was recorded on a scale of 0 – 50 and grouped into none/ mild (score 0 – 10), moderate (score 11 – 20) and severe (score 21 – 50). Severity of pleurisy was scored on a 0 – 2 scale with a separate variable for lungs that were attached to the chest wall (score 2). These lungs could not be assessed for other lung lesions and therefore a separate database was created for assessing the pleurisy lesions (n = 5,628) while the final database contained animals (n = 4,491) with records for tail lesions, EP-like lesion scores and pleurisy (level 0 + 1). Associations between tail lesions and sex and the different lung lesion outcomes were analysed using generalized linear mixed models (PROC GLIMMIX) with random effect for batch. EP-like lesions and pleurisy were the most common lesions, though large variation existed between batches. Pigs with severe tail lesions tended to have more severe pleurisy where the lungs remained attached to the chest wall than pigs with moderate tail lesions. No other associations between tail lesion scores and lung lesions were found. Although tail lesions on the carcass may not be an accurate predictor of lung health, tail lesions are important welfare indicators and respiratory disease is among the most significant infectious conditions affecting pigs. Thus, recording of tail and lung lesions at meat inspection provides valuable information regarding the on-farm health welfare of pigs

Impact and collaboration in environmental research: moving universities from evidence producers to co-producers

This discussion paper explores the relationship between environmental research and its use in environmental policy. While there is a common perception of a gap between research and policy, efforts to bridge it often fall short of integrating knowledge effectively with environmental action. Common fixes, like improving dissemination and scientific literacy within government, overlook the politics and complexities of knowledge production and usage. We explore universities’ pivotal position in the science-policy ecosystem, particularly given their role in knowledge brokerage practices and the influence of ‘impact’ as a governance tool. Participatory approaches, such as co-production, offer promise for closing the ‘usability gap’ for research by facilitating collaborative generation of actionable knowledge. Co-production features high user participation, contributing to higher-quality research, fostering trust, and giving voice to knowledge users and interested parties. Understood and deployed in various ways, co-production also faces challenges such as the high potential costs or replication of wider knowledge production risks. A reflective approach to co-production, considering positionality and recognising political influences, can mitigate these risks and optimise its benefits. We highlight the potential of co-production in environmental research and policy and offers valuable insights and recommendations for its effective implementation. We hope that the material in this discussion paper provides a constructive basis for precipitating reflections and discussions amongst researchers and other people involved in the production and use of environmental research about their role in engaging with policy

Impact and collaboration in environmental research moving universities from evidence producers to co-producers – summary paper

This document is a summary of a discussion document that explores the relationship between environmental research and policy, the role of universities, and the emergence of co-production. It provides a set of provocative discussion questions to help funders, policy makers, practitioners, and researchers engage with these topics. The report was launched in June 2024, a recording of the launch webinar can be found on the Agile website

ROSAT Blank Field Sources I: Sample Selection and Archival Data

We have identified a population of blank field sources (or `blanks') among the ROSAT bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of blanks is not compatible with the main classes of X-ray emitters except for extreme BL Lacertae objects. From the analysis of ROSAT archival data we found no indication of variability and evidence for only three sources, out of 16, needing absorption in excess of the Galactic value. We also found evidence for an extended nature for only one of the 5 blanks with a serendipitous HRI detection; this source (1WGAJ1226.9+3332) was confirmed as a z=0.89 cluster of galaxies. Palomar images reveal the presence of a red (O-E~2) counterpart in the X-ray error circle for 6 blanks. The identification process brought to the discovery of another high z cluster of galaxies, one (possibly extreme) BL Lac, two ultraluminous X-ray sources in nearby galaxies and two apparently normal type1 AGNs. These AGNs, together with 4 more AGN-like objects seem to form a well defined group: they present unabsorbed X-ray spectra but red Palomar counterparts. We discuss the possible explanations for the discrepancy between the X-ray and optical data, among which: a suppressed big blue bump emission, an extreme dust to gas (~40-60 the Galactic ratio), a high redshift (z>3.5) QSO nature, an atypical dust grain size distribution and a dusty warm absorber. These AGN-like blanks seem to be the bright (and easier to study) analogs of the sources which are found in deep Chandra observations. Three more blanks have a still unknown nature.Comment: 23 pages, 8 figures, accepted by ApJ main journa