The peculiar velocity field: constraining the tilt of the Universe

A large bulk flow, which is in tension with the Lambda Cold Dark Matter ($\Lambda$CDM) cosmological model, has been observed. In this paper, we provide a physically plausible explanation of this bulk flow, based on the assumption that some fraction of the observed dipole in the cosmic microwave background is due to an intrinsic fluctuation, so that the subtraction of the observed dipole leads to a mismatch between the cosmic microwave background (CMB) defined rest frame and the matter rest frame. We investigate a model that takes into account the relative velocity (hereafter the tilted velocity) between the two frames, and develop a Bayesian statistic to explore the likelihood of this tilted velocity. By studying various independent peculiar velocity catalogs, we find that: (1) the magnitude of the tilted velocity $u$ is around 400 km/s, and its direction is close to what is found from previous bulk flow analyses; for most catalogs analysed, u=0 is excluded at about the $2.5 \sigma$ level;(2) constraints on the magnitude of the tilted velocity can result in constraints on the duration of inflation, due to the fact that inflation can neither be too long (no dipole effect) nor too short (very large dipole effect); (3) Under the assumption of a super-horizon isocurvature fluctuation, the constraints on the tilted velocity require that inflation lasts at least 6 e-folds longer (at the 95% confidence interval) than that required to solve the horizon problem. This opens a new window for testing inflation and models of the early Universe from observations of large scale structure.Comment: 7 pages, 7 figures, match the published version in Phys.Rev.

Interactive simulation and visualization

Journal ArticleMost of us perform data analysis and visualization only after everything else is finished, which often means that we don't discover errors invalidating the results of our simulation until postprocessing. A better approach would be to improve the integration of simulation and visualization into the entire process so that you can make adjustments along the way. We call this approach computational steering. Computational steering is the capacity to control all aspects of the computational science pipeline-the succession of steps required to solve computational science and engineering problems. When you interactively explore a simulation in time and space, you steer it. In this sense, you can rely on steering to assist in debugging and to modify the computational aspects of your application

Hidden in plain sight: a massive, dusty starburst in a galaxy protocluster at z=5.7 in the COSMOS field

We report the serendipitous discovery of a dusty, starbursting galaxy at $z=5.667$ (hereafter called CRLE) in close physical association with the "normal" main-sequence galaxy HZ10 at $z=5.654$. CRLE was identified by detection of [CII], [NII] and CO(2-1) line emission, making it the highest redshift, most luminous starburst in the COSMOS field. This massive, dusty galaxy appears to be forming stars at a rate of at least 1500$\,M_\odot$ yr$^{-1}$ in a compact region only $\sim3$ kpc in diameter. The dynamical and dust emission properties of CRLE suggest an ongoing merger driving the starburst, in a potentially intermediate stage relative to other known dusty galaxies at the same epoch. The ratio of [CII] to [NII] may suggest that an important ($\sim15\%$) contribution to the [CII] emission comes from a diffuse ionized gas component, which could be more extended than the dense, starbursting gas. CRLE appears to be located in a significant galaxy overdensity at the same redshift, potentially associated with a large-scale cosmic structure recently identified in a Lyman Alpha Emitter survey. This overdensity suggests that CRLE and HZ10 reside in a protocluster environment, offering the tantalizing opportunity to study the effect of a massive starburst on protocluster star formation. Our findings support the interpretation that a significant fraction of the earliest galaxy formation may occur from the inside out, within the central regions of the most massive halos, while rapidly evolving into the massive galaxy clusters observed in the local Universe.Comment: 16 pages, 9 figures, 4 tables, final version to appear on ApJ (accepted May 19, 2018

The Poisson-Boltzmann model for implicit solvation of electrolyte solutions: Quantum chemical implementation and assessment via Sechenov coefficients.

We present the theory and implementation of a Poisson-Boltzmann implicit solvation model for electrolyte solutions. This model can be combined with arbitrary electronic structure methods that provide an accurate charge density of the solute. A hierarchy of approximations for this model includes a linear approximation for weak electrostatic potentials, finite size of the mobile electrolyte ions, and a Stern-layer correction. Recasting the Poisson-Boltzmann equations into Euler-Lagrange equations then significantly simplifies the derivation of the free energy of solvation for these approximate models. The parameters of the model are either fit directly to experimental observables-e.g., the finite ion size-or optimized for agreement with experimental results. Experimental data for this optimization are available in the form of Sechenov coefficients that describe the linear dependence of the salting-out effect of solutes with respect to the electrolyte concentration. In the final part, we rationalize the qualitative disagreement of the finite ion size modification to the Poisson-Boltzmann model with experimental observations by taking into account the electrolyte concentration dependence of the Stern layer. A route toward a revised model that captures the experimental observations while including the finite ion size effects is then outlined. This implementation paves the way for the study of electrochemical and electrocatalytic processes of molecules and cluster models with accurate electronic structure methods

Heart rate variability in insomnia patients: A critical review of the literature

Heart rate variability (HRV) is an objective marker that provides insight into autonomic nervous system dynamics. There is conflicting evidence regarding the presence of HRV impairment in insomnia patients. Web-based databases were used to systematically search the literature for all studies that compared the HRV of insomnia patients to controls or reported the HRV of insomnia patients before and after an intervention. 22 relevant papers were identified. Study characteristics were summarised, HRV measures were extracted and a risk of bias assessment for each study was performed. We were limited in our ability to synthesise outcome measures and perform meta-analyses due to considerable differences in patient (and control) selection, study protocols, measurement and processing techniques and outcome reporting. Risk of bias was deemed to be high in the majority of studies. As such, we cannot confirm that HRV is reliably impaired in insomnia patients nor determine the HRV response to interventions. Whilst HRV impairment in insomnia is a widely accepted concept, it is not supported by empirical evidence. Large longitudinal studies incorporating 24-hour recordings are required to elucidate the precise nature of HRV dynamics in insomnia patients