304 research outputs found
CMBPol Mission Concept Study: Probing Inflation with CMB Polarization
We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of inflation. We focus on the prospects for using CMB measurements to differentiate various inflationary mechanisms. In particular, a detection of primordial B-mode polarization would demonstrate that inflation occurred at a very high energy scale, and that the inflaton traversed a super-Planckian distance in field space. We explain how such a detection or constraint would illuminate aspects of physics at the Planck scale. Moreover, CMB measurements can constrain the scale-dependence and non-Gaussianity of the primordial fluctuations and limit the possibility of a significant isocurvature contribution. Each such limit provides crucial information on the underlying inflationary dynamics. Finally, we quantify these considerations by presenting forecasts for the sensitivities of a future satellite experiment to the inflationary parameters
Reionization and the large-scale 21 cm-cosmic microwave background cross correlation
Of the many probes of reionization, the 21 cm line and the cosmic microwave
background (CMB) are among the most effective. We examine how the
cross-correlation of the 21 cm brightness and the CMB Doppler fluctuations on
large angular scales can be used to study this epoch. We employ a new model of
the growth of large scale fluctuations of the ionized fraction as reionization
proceeds. We take into account the peculiar velocity field of baryons and show
that its effect on the cross correlation can be interpreted as a mixing of
Fourier modes. We find that the cross-correlation signal is strongly peaked
toward the end of reionization and that the sign of the correlation should be
positive because of the inhomogeneity inherent to reionization. The signal
peaks at degree scales (l~100) and comes almost entirely from large physical
scales (k~0.01 Mpc). Since many of the foregrounds and noise that plague low
frequency radio observations will not correlate with CMB measurements, the
cross correlation might appear to provide a robust diagnostic of the
cosmological origin of the 21 cm radiation around the epoch of reionization.
Unfortunately, we show that these signals are actually only weakly correlated
and that cosmic variance dominates the error budget of any attempted detection.
We conclude that the detection of a cross-correlation peak at degree-size
angular scales is unlikely even with ideal experiments.Comment: 15 pages, 4 figures, submitted to MNRA
Impact of homicide by a psychiatric patient on forensic psychiatrists: national survey
Aims and method
To explore the experiences and support needs of consultant forensic psychiatrists, whose patients had committed homicide while under their care. We circulated a survey to all forensic psychiatrists in the UK, through the Royal College of Psychiatrists, asking about their experiences of a homicide by a patient under their care. Respondents were invited to discuss their experiences further in a structured telephone interview and themes were identified from these discussions. Data were analysed quantitatively and qualitatively.
Results
One-third of the 86 respondents had had at least one patient who had committed a homicide while under their care. Of these, over three-quarters (78%) reported that the homicide had a significant impact on their personal life, professional life and/or mental/physical health. For some respondents, the impact was severe and long term. Respondents generally felt that they would have been helped by receiving more support in the aftermath of the homicide.
Clinical implications
Greater recognition is needed of the impact on treating psychiatrists of homicide by a patient and more support is needed for affected clinicians. Further research is necessary, including the effects of such events on colleagues in other specialties and examination of the costs versus the benefits of mandatory inquiries after homicides
'Moving on' through the locked ward system for women with intellectual disabilities
Background: The move to community support for all people with intellectual disabilities is an aspiration with international significance. In this article we draw on rich accounts from women with intellectual disabilities detained under the Mental Health Act (E&W) 1983 and staff at an National Health Service secure setting in England to explore how âmoving onâ is defined and perceived. Methods: The study reports on an ethnographic study using the field-notes and the 26 semi-structured interviews with detained women and staff on three wards. Results: We first explore staff conceptions of moving on, which include behavioural change and utilising coping strategies. Then we discuss the areas of analysis that women discussed: taking back responsibility, success in arranged relationships, acceptance of regime and resistance to progression. Conclusion: The concepts of moving on were not determined by the women but by the service. We recommend further research which explores womenâs own rehabilitation requirements
Primordial Black Holes, Eternal Inflation, and the Inflationary Parameter Space after WMAP5
We consider constraints on inflation driven by a single, minimally coupled
scalar field in the light of the WMAP5 dataset, as well as ACBAR and the
SuperNova Legacy Survey. We use the Slow Roll Reconstruction algorithm to
derive optimal constraints on the inflationary parameter space. The scale
dependence in the slope of the scalar spectrum permitted by WMAP5 is large
enough to lead to viable models where the small scale perturbations have a
substantial amplitude when extrapolated to the end of inflation. We find that
excluding parameter values which would cause the overproduction of primordial
black holes or even the onset of eternal inflation leads to potentially
significant constraints on the slow roll parameters. Finally, we present a more
sophisticated approach to including priors based on the total duration of
inflation, and discuss the resulting restrictions on the inflationary parameter
space.Comment: v2: version published in JCAP. Minor clarifications and references
adde
Loop Corrections to Cosmological Perturbations in Multi-field Inflationary Models
We investigate one-loop quantum corrections to the power spectrum of
adiabatic perturbation from entropy modes/adiabatic mode cross-interactions in
multiple DBI inflationary models. We find that due to the non-canonical kinetic
term in DBI models, the loop corrections are enhanced by slow-varying parameter
and small sound speed . Thus, in general the loop-corrections
in multi-DBI models can be large. Moreover, we find that the loop-corrections
from adiabatic/entropy cross-interaction vertices are IR finite.Comment: 21 pages, 7 figures; v2, typos corrected, ref added; v3 typos
corrected, version for publishing in jca
Probing the primordial power spectra with inflationary priors
We investigate constraints on power spectra of the primordial curvature and
tensor perturbations with priors based on single-field slow-roll inflation
models. We stochastically draw the Hubble slow-roll parameters and generate the
primordial power spectra using the inflationary flow equations. Using data from
recent observations of CMB and several measurements of geometrical distances in
the late Universe, Bayesian parameter estimation and model selection are
performed for models that have separate priors on the slow-roll parameters. The
same analysis is also performed adopting the standard parameterization of the
primordial power spectra. We confirmed that the scale-invariant
Harrison-Zel'dovich spectrum is disfavored with increased significance from
previous studies. While current observations appear to be optimally modeled
with some simple models of single-field slow-roll inflation, data is not enough
constraining to distinguish these models.Comment: 23 pages, 3 figures, 7 tables, accepted for publication in JCA
Single-field inflation constraints from CMB and SDSS data
We present constraints on canonical single-field inflation derived from WMAP
five year, ACBAR, QUAD, BICEP data combined with the halo power spectrum from
SDSS LRG7. Models with a non-scale-invariant spectrum and a red tilt n_s < 1
are now preferred over the Harrison-Zel'dovich model (n_s = 1, tensor-to-scalar
ratio r = 0) at high significance. Assuming no running of the spectral indices,
we derive constraints on the parameters (n_s, r) and compare our results with
the predictions of simple inflationary models. The marginalised credible
intervals read n_s = 0.962^{+0.028}_{-0.026} and r < 0.17 (at 95% confidence
level). Interestingly, the 68% c.l. contours favour mainly models with a convex
potential in the observable region, but the quadratic potential model remains
inside the 95% c.l. contours. We demonstrate that these results are robust to
changes in the datasets considered and in the theoretical assumptions made. We
then consider a non-vanishing running of the spectral indices by employing
different methods, non-parametric but approximate, or parametric but exact.
With our combination of CMB and LSS data, running models are preferred over
power-law models only by a Delta chi^2 ~ 5.8, allowing inflationary stages
producing a sizable negative running -0.063^{+0.061}_{-0.049} and larger
tensor-scalar ratio r < 0.33 at the 95% c.l. This requires large values of the
third derivative of the inflaton potential within the observable range. We
derive bounds on this derivative under the assumption that the inflaton
potential can be approximated as a third order polynomial within the observable
range.Comment: 32 pages, 7 figures. v2: additional references, some typos corrected,
passed to JCAP style. v3: minor changes, matches published versio
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