Dark Matter Halos from the Inside Out

The balance of evidence indicates that individual galaxies and groups or clusters of galaxies are embedded in enormous distributions of cold, weakly interacting dark matter. These dark matter 'halos' provide the scaffolding for all luminous structure in the universe, and their properties comprise an essential part of the current cosmological model. I review the internal properties of dark matter halos, focussing on the simple, universal trends predicted by numerical simulations of structure formation. Simulations indicate that halos should all have roughly the same spherically-averaged density profile and kinematic structure, and predict simple distributions of shape, formation history and substructure in density and kinematics, over an enormous range of halo mass and for all common variants of the concordance cosmology. I describe observational progress towards testing these predictions by measuring masses, shapes, profiles and substructure in real halos, using baryonic tracers or gravitational lensing. An important property of simulated halos (possibly the most important property) is their dynamical 'age', or degree of internal relaxation. The age of a halo may have almost as much effect as its mass in determining the state of its baryonic contents, so halo ages are also worth trying to measure observationally. I review recent gravitational lensing studies of galaxy clusters which should measure substructure and relaxation in a large sample of individual cluster halos, producing quantitative measures of age that are well-matched to theoretical predictions. The age distributions inferred from these studies will lead to second-generation tests of the cosmological model, as well as an improved understanding of cluster assembly and the evolution of galaxies within clusters.Comment: v2: additional references and minor corrections to match the published versio

ASSESSING THE RELATIVE INFLUENCES OF ABIOTIC AND BIOTIC FACTORS ON A SPECIES’ DISTRIBUTION USING PSEUDO-ABSENCE AND FUNCTIONAL TRAIT DATA: A CASE STUDY WITH THE AMERICAN EEL (Anguilla rostrata)

Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi-species datasets. Here, we present a flexible method to compare abiotic and biotic influences at common scales. First, data representing abiotic and biotic factors are collected using a combination of geographic information system, remotely sensed, and species’ functional trait data. Next, the relative influences of each predictor variable on the occurrence of a focal species are compared. Specifically, ‘sample’ data from sites of known occurrence are compared with ‘background’ data (i.e. pseudo-absence data collected at sites where occurrence is unknown, combined with sample data). Predictor variables that may have the strongest influence on the focal species are identified as those where sample data are clearly distinct from the corresponding background distribution. To demonstrate the method, effects of hydrology, physical habitat, and co-occurring fish functional traits are assessed relative to the contemporary (1950 – 1990) distribution of the American Eel (Anguilla rostrata) in six Mid-Atlantic (USA) rivers. We find that Eel distribution has likely been influenced by the functional characteristics of co-occurring fishes and by local dam density, but not by other physical habitat or hydrologic factors

Polarization diversity monopulse tracking receiver Patent

Polarization diversity monopulse tracking receiver design without radio frequency switche

Classification of Links Up to 0-Solvability

The $n$-solvable filtration of the $m$-component smooth (string) link concordance group, $$\dots \subset \mathcal{F}^m_{n+1} \subset \mathcal{F}^m_{n.5} \subset \mathcal{F}^m_n \dots \subset \mathcal{F}^m_1 \subset \mathcal{F}^m_{0.5} \subset \mathcal{F}^m_0 \subset \mathcal{F}^m_{-0.5} \subset \mathcal{C}^m,$$ as defined by Cochran, Orr, and Teichner, is a tool for studying smooth knot and link concordance that yields important results in low-dimensional topology. The focus of this paper is to give a characterization of the set of 0-solvable links. We introduce a new equivalence relation on links called 0-solve equivalence and establish both an algebraic and a geometric classification of $\mathbb{L}_0^m$, the set of links up to 0-solve equivalence. We show that $\mathbb{L}_0^m$ has a group structure isomorphic to the quotient $\mathcal{F}_{-0.5}/\mathcal{F}_0$ of concordance classes of string links and classify this group, showing that $$\mathbb{L}_0^m \cong \mathcal{F}_{-0.5}^m/\mathcal{F}_0^m \cong \mathbb{Z}_2^m \oplus \mathbb{Z}^{m \choose 3} \oplus \mathbb{Z}_2^{m \choose 2}.$$ Finally, using results of Conant, Schneiderman, and Teichner, we show that 0-solvable links are precisely the links that bound class 2 gropes and support order 2 Whitney towers in the 4-ball.Comment: 34 page

Solar cell metallization: Historical perspective

Solar cell metallization design requirements are discussed. Space applications and terrestrial applications are considered. Cost factors are discussed in relation to design analysis

The Adiabatic Motion of Outer Zone Particles in a Model of the Geoelectric and Geomagnetic Fields

Charged particle motion calculations from model of earths magnetospher

The latitude - local time dependence of low energy cosmic ray cut-offs in a realistic geomagnetic field

Latitude - local time dependence of low energy cosmic ray cut-offs in realistic geomagnetic fiel