Non-Gaussianity from Step Features in the Inflationary Potential

We provide analytic solutions for the power spectrum and bispectrum of curvature fluctuations produced by a step feature in the inflaton potential, valid in the limit that the step is short and sharp. In this limit, the bispectrum is strongly scale dependent and its effective non-linearity attains a large oscillatory amplitude. The perturbations to the curvature power spectrum, on the other hand, remain a small component on top of the usual spectrum of fluctuations generated by slow roll. We utilize our analytic solutions to assess the observability of the predicted non-Gaussian signatures and show that, if present, only very sharp steps on scales larger than ~ 2 Gpc are likely to be able to be detected by Planck. Such features are not only consistent with WMAP7 data, but can also improve its likelihood by 2 Delta ln L ~ 12 for two extra parameters, the step location and height. If this improvement were due to a slow roll violating step as considered here, a bispectrum or corresponding polarization power spectrum detection would provide definitive checks as to its primordial origin.Comment: Typos fixed, supersedes journal versio

Scattering systems with several evolutions and formal reproducing kernel Hilbert spaces

A Schur-class function in $d$ variables is defined to be an analytic contractive-operator valued function on the unit polydisk. Such a function is said to be in the Schur--Agler class if it is contractive when evaluated on any commutative $d$-tuple of strict contractions on a Hilbert space. It is known that the Schur--Agler class is a strictly proper subclass of the Schur class if the number of variables $d$ is more than two. The Schur--Agler class is also characterized as those functions arising as the transfer function of a certain type (Givone--Roesser) of conservative multidimensional linear system. Previous work of the authors identified the Schur--Agler class as those Schur-class functions which arise as the scattering matrix for a certain type of (not necessarily minimal) Lax--Phillips multievolution scattering system having some additional geometric structure. The present paper links this additional geometric scattering structure directly with a known reproducing-kernel characterization of the Schur--Agler class. We use extensively the technique of formal reproducing kernel Hilbert spaces that was previously introduced by the authors and that allows us to manipulate formal power series in several commuting variables and their inverses (e.g., Fourier series of elements of $L^2$ on a torus) in the same way as one manipulates analytic functions in the usual setting of reproducing kernel Hilbert spaces

Metal Enrichment of the ICM: a 3-D Picture of Chemical and Dynamical Properties

We develop a model for the metal enrichment of the intracluster medium (ICM) that combines a cosmological non-radiative hydrodynamical N-Body/SPH simulation of a cluster of galaxies, and a semi-analytic model of galaxy formation. The novel feature of our hybrid model is that the chemical properties of the diffuse gas in the underlying simulation are dynamically and consistently generated from stars in the galaxies. We follow the production of several chemical elements, provided by low- and intermediate-mass stars, core collapse and type Ia supernovae. We analyse the spatial distribution of metals in the ICM, investigate the way in which the chemical enrichment proceeds, and use iron emissivity as a tracer of gas motions. Fe and O radial abundance profiles are enhanced in the inner 100 h^-1 kpc in the last Gyr because of the convergence of enriched gas clumps to the cluster centre. Our results support a scenario in which part of the central intracluster gas comes from gas clumps that, in the redshift range of z~0.2 to ~0.5, have been enriched to solar values and are at large distances from the cluster centre (from ~1 to ~6 h^-1 Mpc) moving at very high velocities (from ~1300 to ~2500 km s^-1). The turbulent gas motions within the cluster, originated in the inhomogeneous gas infall during the cluster assembly, are manifested in emission-weighted velocity maps as gradients that can be as large as ~1000 km s^-1 over distances of a few hundred kpc. Gradients of this magnitude are also seen in velocity distributions along sightlines through the cluster centre. Doppler shifting and broadening suffered by the Fe K 6.7 keV emission line along such sightlines could be used to probe these gas large-scale motions when they are produced within an area characterised by high iron line emissivity.Comment: 24 pages, 13 figures, accepted for publication in MNRA

INTEGRATED GEOPHYSICAL IMAGING OF SUBSURFACE GEOLOGIC CONDITIONS ACROSS A CONTAMINANT PLUME, MCCRACKEN COUNTY, KENTUCKY

Over 7.8 km of seismic reflection data and 2 km of electrical resistivity data were acquired, processed, and interpreted during this multi-method geophysical study. Objectives included the definition of geologic conditions underlying a contaminant plume in McCracken County, western Kentucky, and the determination of the potential for structural control on the rate and direction of plume migration. Both geophysical methods indicate the presence of multiple high-angle normal faults outlining a series of asymmetric grabens ranging in width from 160 m to almost 300 m and striking between N40°E and N45°E. There was agreement between the two methods on fault location and degree of near-surface offset, with offsets of 1 to 2 m observed at 10 to 20 m below ground surface and 3 to 8 m observed at 20 to 30 m depth. Bedrock displacement was generally 2 to 3 times larger, with offsets of 10 to 26 m observed. The faults appear to have originated in the Paleozoic with predominantly normal reactivation occurring as recently as the Pleistocene. The fault strikes generally approximate the orientation of the northwestern contaminant plume. Observed offset of the Regional Gravel Aquifer may form a preferential flow path for contaminant migration

A study of the qualifications and of the preparations of the field teacher in selected public health agencies.

Thesis (M.S.)--Boston Universit

Development of the Red Sequence in Galaxy Clusters

We investigate the origin of the color-magnitude relation (CMR) observed in cluster galaxies by using a combination of a cosmological N-body simulation of a cluster of galaxies and a semi-analytic model of galaxy formation. The departure of galaxies in the bright end of the CMR with respect to the trend defined by less luminous galaxies could be explained by the influence of minor mergers.Comment: Proceedings IAU Symposium No. 267, 2009. Co-Evolution of Central Black Holes and Galaxie