2,841 research outputs found
VLT Observations of Two Unusual BAL Quasars
Among the unusual broad absorption line quasars being found by the Sloan
Digital Sky Survey (SDSS) are objects with much stronger absorption in Fe III
than Fe II. These unusual line ratios require a high density in the outflow
(n_H >= 3 x 10^{10} cm^{-3}). They should also appear for only a limited range
of outflow column densities, which explains their rarity. Previously we
suggested that the Fe III line ratios were also affected by a resonance; we now
believe this is an artifact of structure in the underlying Fe II + Fe III
pseudocontinuum. The SDSS is also discovering objects with absorption in rarely
seen transitions such as He I. VLT+UVES high-resolution spectra of one such
object, the mini-BAL quasar SDSS 1453+0029, show that it has two He I
absorption systems with considerably different properties separated by only 350
km/s.Comment: 4 pages, 3 figures; to appear in "Active Galactic Nuclei, from
Central Engine to Host Galaxy", eds. Collin, Combes & Shlosman, PASP
Conference Series, in pres
Investigating Multiple Solutions in the Constrained Minimal Supersymmetric Standard Model
Recent work has shown that the Constrained Minimal Supersymmetric Standard
Model (CMSSM) can possess several distinct solutions for certain values of its
parameters. The extra solutions were not previously found by public
supersymmetric spectrum generators because fixed point iteration (the algorithm
used by the generators) is unstable in the neighbourhood of these solutions.
The existence of the additional solutions calls into question the robustness of
exclusion limits derived from collider experiments and cosmological
observations upon the CMSSM, because limits were only placed on one of the
solutions. Here, we map the CMSSM by exploring its multi-dimensional parameter
space using the shooting method, which is not subject to the stability issues
which can plague fixed point iteration. We are able to find multiple solutions
where in all previous literature only one was found. The multiple solutions are
of two distinct classes. One class, close to the border of bad electroweak
symmetry breaking, is disfavoured by LEP2 searches for neutralinos and
charginos. The other class has sparticles that are heavy enough to evade the
LEP2 bounds. Chargino masses may differ by up to around 10% between the
different solutions, whereas other sparticle masses differ at the sub-percent
level. The prediction for the dark matter relic density can vary by a hundred
percent or more between the different solutions, so analyses employing the dark
matter constraint are incomplete without their inclusion.Comment: 30 pages, 12 figures, 2 tables; v2: added discussion on speed of
shooting method, fixed typos, matches published versio
Warm DBI Inflation
We propose a warm inflationary model in the context of relativistic D-brane
inflation in a warped throat, which has Dirac-Born-Infeld (DBI) kinetic term
and is coupled to radiation through a dissipation term. The perturbation
freezes at the sound horizon and the power spectrum is determined by a
combination of the dissipative parameter and the sound speed parameter. The
thermal dissipation ameliorates the {\it eta} problem and softens theoretical
constraints from the extra-dimensional volume and from observational bounds on
the tensor-to-scalar ratio. The warm DBI model can lead to appreciable
non-Gaussianity of the equilateral type. As a phenomenological model, ignoring
compactification constraints, we show that large-field warm inflation models do
not necessarily yield a large tensor-to-scalar ratio.Comment: 5 pages, 1 figure, IPMU-10-019
The Changing Narratives of Death, Dying, and HIV in the United Kingdom
Death and infection were closely linked from the start of the HIV epidemic, until successful treatments became available. The initial impact of mostly young, gay men dying from HIV was powerful in shaping UK responses. Neoliberal discourses developed at the same time, particularly focusing on how citizens (rather than the state) should take responsibility to improve health. Subsequently “successful ageing” became an allied discourse, further marginalising death discussions. Our study reflected on a broad range of meanings around death within the historical UK epidemic, to examine how dying narratives shape contemporary HIV experiences. Fifty-one participants including people living with HIV, professionals, and activists were recruited for semistructured interviews. Assuming a symbolic interactionist framework, analysis highlighted how HIV deaths were initially experienced as not only traumatic but also energizing, leading to creativity. With effective antiretrovirals, dying changed shape (e.g., loss of death literacy), and better integration of palliative care was recommended
Bug propagation and debugging in asymmetric software structures
Software dependence networks are shown to be scale-free and asymmetric. We
then study how software components are affected by the failure of one of them,
and the inverse problem of locating the faulty component. Software at all
levels is fragile with respect to the failure of a random single component.
Locating a faulty component is easy if the failures only affect their nearest
neighbors, while it is hard if the failures propagate further.Comment: 4 pages, 4 figure
An extremal model for amorphous media plasticity
An extremal model for the plasticity of amorphous materials is studied in a
simple two-dimensional anti-plane geometry. The steady-state is analyzed
through numerical simulations. Long-range spatial and temporal correlations in
local slip events are shown to develop, leading to non-trivial and highly
anisotropic scaling laws. In particular, the plastic strain is shown to
statistically concentrate over a region which tends to align perpendicular to
the displacement gradient. By construction, the model can be seen as giving
rise to a depinning transition, the threshold of which (i.e. the macroscopic
yield stress) also reveal scaling properties reflecting the localization of the
activity.Comment: 4 pages, 5 figure
Sperm donors’ accounts of lesbian recipients: heterosexualisation as a tool for warranting claims to children’s ‘best interests’
This is an Accepted Manuscript of an article published by Taylor & Francis in Psychology and Sexuality on 14 Mar 2013, available online: http://wwww.tandfonline.com/10.1080/19419899.2013.764921.Whilst there exists a considerable body of research documenting heterosexual couples’ use of donor sperm, relatively little is known about the experiences of lesbian recipients of donor sperm and the men who donate to them. Moreover, in all aspects of donor conception there is an ongoing debate over what constitutes children’s ‘best interests’, with this being most problematic in the unregulated private sector (of which lesbian use of donor sperm from gay men constitutes the largest portion). This article presents narratives of a sample of 16 gay men and one heterosexual man who had donated or who were in the process of donating sperm to lesbian recipients. Specifically, the article focuses on the ways in which the majority of the men elaborated a narrative in which their relationship to the birth mother was ‘heterosexualised’, a narrative that functioned to attribute to them a considerable role in determining the ‘best interests’ of donor-conceived children. The article concludes by providing suggestions for legislation and policy stemming from the findings, and recommends that greater attention be paid to the voices of donor-conceived children
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