The Knotted Sky II: Does BICEP2 require a nontrivial primordial power spectrum?

An inflationary gravitational wave background consistent with BICEP2 is difficult to reconcile with a simple power-law spectrum of primordial scalar perturbations. Tensor modes contribute to the temperature anisotropies at multipoles with $l\lesssim 100$, and this effect --- together with a prior on the form of the scalar perturbations --- was the source of previous bounds on the tensor-to-scalar ratio. We compute Bayesian evidence for combined fits to BICEP2 and Planck for three nontrivial primordial spectra: a) a running spectral index, b) a cutoff at fixed wavenumber, and c) a spectrum described by a linear spline with a single internal knot. We find no evidence for a cutoff, weak evidence for a running index, and significant evidence for a "broken" spectrum. Taken at face-value, the BICEP2 results require two new inflationary parameters in order to describe both the broken scale invariance in the perturbation spectrum and the observed tensor-to-scalar ratio. Alternatively, this tension may be resolved by additional data and more detailed analyses.Comment: 14 pages, 5 figures, 4 tables; v2: references added, discussion updated, matches published versio

The Knotted Sky I: Planck constraints on the primordial power spectrum

Using the temperature data from Planck we search for departures from a power-law primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with $n$ knots located at arbitrary values of $\log{k}$, with both linear and cubic splines. This formulation recovers both slow modulations and sharp transitions in the primordial spectrum. The power spectrum is well-fit by a featureless, power-law at wavenumbers $k>10^{-3} \, \mathrm{Mpc}^{-1}$. A modulated primordial spectrum yields a better fit relative to $\Lambda$CDM at large scales, but there is no strong evidence for a departure from a power-law spectrum. Moreover, using simulated maps we show that a local feature at $k \sim 10^{-3} \, \mathrm{Mpc}^{-1}$ can mimic the suppression of large-scale power. With multi-knot spectra we see only small changes in the posterior distributions for the other free parameters in the standard $\Lambda$CDM universe. Lastly, we investigate whether the hemispherical power asymmetry is explained by independent features in the primordial power spectrum in each ecliptic hemisphere, but find no significant differences between them.Comment: 24 pages, 9 figures, 4 tables, 1 appendix; v2: references added, discussion updated, matches published versio

Testing for New Physics: Neutrinos and the Primordial Power Spectrum

We test the sensitivity of neutrino parameter constraints from combinations of CMB and LSS data sets to the assumed form of the primordial power spectrum (PPS) using Bayesian model selection. Significantly, none of the tested combinations, including recent high-precision local measurements of $\mathrm{H}_0$ and cluster abundances, indicate a signal for massive neutrinos or extra relativistic degrees of freedom. For PPS models with a large, but fixed number of degrees of freedom, neutrino parameter constraints do not change significantly if the location of any features in the PPS are allowed to vary, although neutrino constraints are more sensitive to PPS features if they are known a priori to exist at fixed intervals in $\log k$. Although there is no support for a non-standard neutrino sector from constraints on both neutrino mass and relativistic energy density, we see surprisingly strong evidence for features in the PPS when it is constrained with data from Planck 2015, SZ cluster counts, and recent high-precision local measurements of $\mathrm{H}_0$. Conversely combining Planck with matter power spectrum and BAO measurements yields a much weaker constraint. Given that this result is sensitive to the choice of data this tension between SZ cluster counts, Planck and $\mathrm{H}_0$ measurements is likely an indication of unmodeled systematic bias that mimics PPS features, rather than new physics in the PPS or neutrino sector.Comment: 23 pages, 9 figures, 8 tables; matches version published in JCA

Becoming in touch with industrial robots through ethnography

Touch is central to communication and social interaction. For both humans and robots touch is a mode through which they sense the world. A second wave of industrial robots is reshaping how touch operates within the labor process. Recent studies have turned their attention to the role of touch in Human-Robot Interaction (HRI). While these studies have produced useful knowledge in relation to the affective capacities of robotic touch, methods remain restrictive. This paper contributes to expanding research methods for the study of robotic touch. It reports on the design of an ongoing ethnography that forms part of the InTouch project. The interdisciplinary project takes forward a socially orientated stance and is concerned with how technologies shape the semiotic and sensory dimensions of touch in the 'real world'. We contend that these dimensions are key factors in shaping how humans and robots interact, yet are currently overlooked in the HRI community. This multi-sited sensory ethnography research has been designed to explore the social implications of robotic touch within industrial settings (e.g. manufacturing and construction)

Making sense of digitally remediated touch in virtual reality experiences

Touch, often called the ‘first sense’, is fundamental to how we experience and know ourselves, others and the world. Increasingly, touch is being brought into the digital landscape. This paper explores this shifting landscape to understand the ways in which touch is re-mediated in the context of virtual reality. With attention to the sensoriality and sociality of touch, it asks what ‘counts’ as touch in VR, how is touch experienced and how is it incorporated into meaning making. We present and discuss findings from a multimodal and multisensory study of 16 participants interacting in two VR experiences to describe: the participants’ material encounters with the virtual through a focus on touch practices, expectations and norms; the ways in which participants made meaning of (and with) virtual touch through their dynamic selection and orchestration of the range of semiotic and experiential resources available; and how these virtual touch experiences translated into discourses of touch in VR to emphasize continuities and change between the past, present and futures. The paper comments on the methodological challenges of researching touch in the emergent landscape of VR and asks how multimodality might engage newly with touch, perhaps the most under-rated and neglected of modes and senses, and its digital remediation

Taking an Extended Embodied Perspective of Touch: Connection-Disconnection in iVR

Bringing touch into VR experiences through haptics is considered increasingly important for user engagement and fostering feelings of presence and immersion, yet few qualitative studies have explored users' iVR touch experiences. This paper takes an embodied approach–bringing attention to the tactile-kinaesthetic body–to explore users' wholistic experiences of touch in iVR, moving beyond the cutaneous and tactile elements of “feeling” to elaborate upon themes of movement and kinetics. Our findings show how both touch connections and disconnections emerged though material forms of tactility (the controller, body positioning, tactile expectations) and through “felt proximities” and the tactile-kinaesthetic experience thus shaping the sense of presence. The analysis shows three key factors that influence connection and disconnection, and how connection is re-navigated or sought at moments of experienced disconnection: a sense of control or agency; identity; and bridging between the material and virtual. This extended notion of touch deepens our understanding of its role in feelings of presence by providing insight into a range of factors related to notions of touch – both physical and virtual–that come into play in creating a sense of connection or presence (e.g., histories, expectations), and highlights the potential for iVR interaction to attend to the body beyond the hands in terms of touch

Electrical switching of magnetic polarity in a multiferroic BiFeO3 device at room temperature

We have directly imaged reversible electrical switching of the cycloidal rotation direction (magnetic polarity) in a (111)-BiFeO3 epitaxial-film device at room temperature by non-resonant x-ray magnetic scattering. Consistent with previous reports, fully relaxed (111)-BiFeO3 epitaxial films consisting of a single ferroelectric domain were found to comprise a sub-micron-scale mosaic of magneto-elastic domains, all sharing a common direction of the magnetic polarity, which was found to switch reversibly upon reversal of the ferroelectric polarization without any measurable change of the magneto-elastic domain population. A real-space polarimetry map of our device clearly distinguished between regions of the sample electrically addressed into the two magnetic states with a resolution of a few tens of micron. Contrary to the general belief that the magneto-electric coupling in BiFeO3 is weak, we find that electrical switching has a dramatic effect on the magnetic structure, with the magnetic moments rotating on average by 90 degrees at every cycle.Comment: 6 pages, 5 figures; corrected figure

Accurate Liability Estimation Improves Power in Ascertained Case Control Studies

Linear mixed models (LMMs) have emerged as the method of choice for confounded genome-wide association studies. However, the performance of LMMs in non-randomly ascertained case-control studies deteriorates with increasing sample size. We propose a framework called LEAP (Liability Estimator As a Phenotype, https://github.com/omerwe/LEAP) that tests for association with estimated latent values corresponding to severity of phenotype, and demonstrate that this can lead to a substantial power increase

Image Coaddition with Temporally Varying Kernels

Large, multi-frequency imaging surveys, such as the Large Synaptic Survey Telescope (LSST), need to do near-real time analysis of very large datasets. This raises a host of statistical and computational problems where standard methods do not work. In this paper, we study a proposed method for combining stacks of images into a single summary image, sometimes referred to as a template. This task is commonly referred to as image coaddition. In part, we focus on a method proposed in previous work, which outlines a procedure for combining stacks of images in an online fashion in the Fourier domain. We evaluate this method by comparing it to two straightforward methods through the use of various criteria and simulations. Note that the goal is not to propose these comparison methods for use in their own right, but to ensure that additional complexity also provides substantially improved performance