Quintessence and Scalar Dark Matter in the Universe

Continuing with previous works, we present a cosmological model in which dark matter and dark energy are modeled by scalar fields $\Phi$ and $\Psi$, respectively, endowed with the scalar potentials $V(\Phi)=V_{o}[ \cosh {(\lambda \sqrt{\kappa_{o}}\Phi)}-1]$ and $\tilde{V}(\Psi)=\tilde{V_{o}}[ \sinh {(\alpha \sqrt{\kappa_{o}}\Psi)}] ^{\beta}$. This model contains 95% of scalar field. We obtain that the scalar dark matter mass is $m_{\Phi}\sim 10^{-26}eV.$ The solution obtained allows us to recover the success of the standard CDM. The implications on the formation of structure are reviewed. We obtain that the minimal cutoff radio for this model is $r_{c}\sim 1.2 kpc.$Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references updated. To appear in Classical and Quantum Gravity as a Letter to the Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI

Single observable concurrence measurement without simultaneous copies

We present a protocol that allows us to obtain the concurrence of any two qubit pure state by performing a minimal and optimal tomography of one of the subsystems through measuring a single observable of an ancillary four dimensional qudit. An implementation for a system of trapped ions is also proposed, which can be achieved with present day experimental techniques.Comment: 4 pages, 1 figur

Galactic Collapse of Scalar Field Dark Matter

We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies.Comment: 4 pages, 3 figue

5D Schwarzschild-Like Spacetimes with Arbitrary Magnetic Field

We find a new class of exact solutions of the five-dimensional Einstein equations whose corresponding four-dimensional spacetime possesses a Schwarzschild-like behavior. The electromagnetic potential depends on a harmonic function and can be choosen to be of a monopole, dipole, etc. field. The solutions are asymptotically flat and for vanishing magnetic field the four metrics are of the Schwarzschild solution. The spacetime is singular in $r=2m$ for higher multipole moments, but regular for monopoles or vanishing magnetic fields in this point. The scalar field posseses a singular behavior. #(Preprint CINVESTAV 15/93)#Comment: 6 pages, LaTeX.

Granulomatous lesions and Mycobacterium avium subsp. paratuberculosis in portuguese wild boars (Sus scrofa)

Granulomatous lesions and Mycobacterium avium subsp. paratuberculosis in portuguese wild boars (Sus scrofa)

High-redshift objects and the generalized Chaplygin gas

Motivated by recent developments in particle physics and cosmology, there has been growing interest in an unified description of dark matter and dark energy scenarios. In this paper we explore observational constraints from age estimates of high-$z$ objects on cosmological models dominated by an exotic fluid with equation of state $p = -A/\rho^{\alpha}$ (the so-called generalized Chaplygin gas) which has the interesting feature of interpolating between non-relativistic matter and negative-pressure dark energy regimes. As a general result we find that, if the age estimates of these objects are correct, they impose very restrictive limits on some of these scenarios.Comment: 5 pages, 3 figures, to appear in Phys. Rev.

Ultra-wide beam scanning using a Conformal Transmit-array for Ka-band

A conformal cylindrical transmit-array (TA) for ultra-wide mechanical beam steering is presented. The curved design allows to overcome the effective aperture size reduction caused by the beam tilt - intrinsic to all types of planar arrays. This design must also deal with the aberrations caused by feed displacement relative to the TA focus. Instead of using the usual unifocal approach, the TA phase correction was designed to have two pseudo-foci. In this way, the intrinsic phase error caused by feed displacement can be smeared among all beams improving the overall scanning performance of the antenna. The TA is composed of a collection of curved 5-layer stacked patches designed for the Ka-band uplink (30 GHz). The aperture has 215x143 mm in plane dimensions. The presented solution provides a 28.9 dBi maximum gain and scanning range up to 80º within 3.9 dB scan loss, which far exceeds the scanning performance of conventional planar TA.info:eu-repo/semantics/acceptedVersio

Reducing beam aberrations of mechanical scanning transmit-array antennas

There is a new demand for high gain antennas capable of achieving wide-angle beam steering in the microwave and millimeter wave (mmW) regimes. This work focuses on transmit-array (TA) antennas that steer the beam using only in-plane displacement of the TA or feed. We showed in previous works that., for some applications., this solution can be a viable alternative to the more costly electronic beam steering of phased arrays. However., it is necessary to balance the trade-offs between several factors such as gain., beam aberrations., antenna size., maximum scanning angle and the complexity of the mechanical steering system. This communication surveys different techniques that we developed to improve the overall scanning performance of these antennas.info:eu-repo/semantics/acceptedVersio

Renal lesions in deer (Cervus elaphus) - Mycobacterium avium subsp. paratuberculosis involvelment

Renal lesions in deer (Cervus elaphus) - Mycobacterium avium subsp. paratuberculosis involvelment

Prototype of a compact mechanically steered Ka-band antenna for satellite on-the-move

We present a functional prototype of a SOTM user terminal antenna based on a planar offset Fresnel lens that implements a new mechanical steering concept previously proposed by the authors. The beam scanning is achieved by inplane translation of the feed (for zenith scanning) and axial rotation of the antenna (for azimuth scanning). The feed is as assembly of a circular polarization patch and a small planar lens. The goal of the small lens is two-fold : to adjust the primary feed directivity for a proper illumination of the main lens and to shift backwards the phase center of the patch, allowing reducing the antenna height. In the developed prototype the measured gain is 27 dBi at 30 GHz with a scan loss of 3 dB for an elevation scanning range between 18° and 53° for full azimuth. The antenna provides good circular polarization, with a cross polarization level below -14 dB. The side lobe level is below -10 dB for all beams positions. The antenna weight is less than 500 grams.info:eu-repo/semantics/acceptedVersio