The science of color and color vision

A survey of color science and color vision

Objectivist reductionism

A survey of arguments for and against the view that colors are physical properties

Flexible format, computer accessed telemetry system

With this system, it is possible to sample and generate two or more simultaneous formats; one can be transmitted to ground station in real time, and other is stored for later transmission. Sensor output comparison data, plus information to control format, compression algorithm, and allowable degree of sensor activity, are stored in memory

Data multiplexer using a tree switch

Self-decoding FET-hybrid or integrated-circuit tree configuration uses minimum number of components and can be sequenced by clock or computer. Redundancy features can readily be incorporated into tree configuration; as tree grows in size and more sensors are included, percentage of parts that will affect given percentage of sensors steadily decreases

Cosmology with the lights off: Standard sirens in the Einstein Telescope era

We explore the prospects for constraining cosmology using gravitational-wave (GW) observations of neutron-star binaries by the proposed Einstein Telescope (ET), exploiting the narrowness of the neutron-star mass function. Double neutron-star (DNS) binaries are expected to be one of the first sources detected after "first-light" of Advanced LIGO and are expected to be detected at a rate of a few tens per year in the advanced era. However the proposed ET could catalog tens of thousands per year. Combining the measured source redshift distributions with GW-network distance determinations will permit not only the precision measurement of background cosmological parameters, but will provide an insight into the astrophysical properties of these DNS systems. Of particular interest will be to probe the distribution of delay times between DNS-binary creation and subsequent merger, as well as the evolution of the star-formation rate density within ET's detection horizon. Keeping H_0, \Omega_{m,0} and \Omega_{\Lambda,0} fixed and investigating the precision with which the dark-energy equation-of-state parameters could be recovered, we found that with 10^5 detected DNS binaries we could constrain these parameters to an accuracy similar to forecasted constraints from future CMB+BAO+SNIa measurements. Furthermore, modeling the merger delay-time distribution as a power-law, and the star-formation rate (SFR) density as a parametrized version of the Porciani and Madau SF2 model, we find that the associated astrophysical parameters are constrained to within ~ 10%. All parameter precisions scaled as 1/sqrt(N), where N is the number of cataloged detections. We also investigated how precisions varied with the intrinsic underlying properties of the Universe and with the distance reach of the network (which may be affected by the low-frequency cutoff of the detector).Comment: 24 pages, 11 figures, 6 tables. Minor changes to reflect published version. References updated and correcte

A linear theory for control of non-linear stochastic systems

We address the role of noise and the issue of efficient computation in stochastic optimal control problems. We consider a class of non-linear control problems that can be formulated as a path integral and where the noise plays the role of temperature. The path integral displays symmetry breaking and there exist a critical noise value that separates regimes where optimal control yields qualitatively different solutions. The path integral can be computed efficiently by Monte Carlo integration or by Laplace approximation, and can therefore be used to solve high dimensional stochastic control problems.Comment: 5 pages, 3 figures. Accepted to PR

Centros de acceso público a las tecnologías de información y comunicación en América Latina: características y desafíos

Incluye BibliografíaEl objetivo principal del presente estudio, fue identificar y caracterizar el mayor número posible de programas de Centros de Acceso Público a las Tecnologías de la Información y Comunicación (CAPT), existentes en los países seleccionados para el estudio. El resultado del mismo es un mapeo que debe ser entendido como una primera aproximación a la situación actual. En este sentido, el levantamiento no proclama ser exhaustivo, ni completo, o estadísticamente representativo, sino un primer paso en un terreno todavía bastante desconocido, pero de crucial importancia para el desarrollo de las Sociedades de la Información en América Latina (AL). No obstante, cabe mencionar que, de acuerdo con la literatura revisada, este estudio es el más extenso y profundo sobre esta temática realizado en la región hasta la fecha. En el marco del estudio, se realizaron un total de 70 entrevistas válidas a responsables de los programas CAPT existentes en la región, en un total de 13 países. La información coleccionada a través de este mecanismo esta definida como fuente primaria (FP). Adicionalmente se recabó información secundaria sobre 151 programas CAPT adicionales (fuente secundaria FS). El estudio está dividido en dos partes: la primera parte muestra los resultados cuantitativos sobre el fenómeno de los CAPT en 14 países de la región de América Latina. Brasil fue incluido en la muestra del estudio, aunque solo se pudo obtener información secundaria. La segunda parte presenta los análisis cualitativos realizados por los investigadores responsables de la realización de las entrevistas. Los resultados de la primera parte muestran como el fenómeno de los CAPT presenta una evolución creciente y con altas perspectivas de sostenibilidad en el tiempo. El estudio, permite tener un primer acercamiento a la realidad de los CAPT a través del análisis del centro promedio y formular algunas recomendaciones que contribuyan al mejoramiento de este tipo de iniciativas. De acuerdo con datos anteriormente disponibles (ver por ejemplo CEPAL, 2005) se estimaba que en 2004 el número de CAPT gubernamentales oscilaba entre 6.000 y 10.000 en toda América Latina. Los resultados obtenidos mediante investigaciones primarias y secundarias de este nuevo sondeo, indican que para el año 2005 el número total de CAPT, tanto gubernamentales como privados, ascendían a 139.064 y se prevee que este número se incremente en años sucesivos

Imaging the Cosmic Matter Distribution using Gravitational Lensing of Pregalactic HI

21-cm emission from neutral hydrogen during and before the epoch of cosmic reionisation is gravitationally lensed by material at all lower redshifts. Low-frequency radio observations of this emission can be used to reconstruct the projected mass distribution of foreground material, both light and dark. We compare the potential imaging capabilities of such 21-cm lensing with those of future galaxy lensing surveys. We use the Millennium Simulation to simulate large-area maps of the lensing convergence with the noise, resolution and redshift-weighting achievable with a variety of idealised observation programmes. We find that the signal-to-noise of 21-cm lens maps can far exceed that of any map made using galaxy lensing. If the irreducible noise limit can be reached with a sufficiently large radio telescope, the projected convergence map provides a high-fidelity image of the true matter distribution, allowing the dark matter halos of individual galaxies to be viewed directly, and giving a wealth of statistical and morphological information about the relative distributions of mass and light. For instrumental designs like that planned for the Square Kilometer Array (SKA), high-fidelity mass imaging may be possible near the resolution limit of the core array of the telescope.Comment: version accepted for publication in MNRAS (reduced-resolution figures

Structure and dynamics of topological defects in a glassy liquid on a negatively curved manifold

We study the low-temperature regime of an atomic liquid on the hyperbolic plane by means of molecular dynamics simulation and we compare the results to a continuum theory of defects in a negatively curved hexagonal background. In agreement with the theory and previous results on positively curved (spherical) surfaces, we find that the atomic configurations consist of isolated defect structures, dubbed "grain boundary scars", that form around an irreducible density of curvature-induced disclinations in an otherwise hexagonal background. We investigate the structure and the dynamics of these grain boundary scars