Mirror Dark Matter

There appear to be three challenges that any theory of dark matter must face: (i) why is $\Omega_{DM}$ of the same order as $\Omega_{Baryons}$ ? (ii) what are the near solar mass objects ($\sim 0.5 M_{\odot}$) observed by the MACHO microlensing project ? and (iii) understanding the shallow core density profile of the halos of dwarf as well as low surface brightness galaxies. The popular cold dark matter candidates, the SUSY LSP and the axion fail to meet these challenges. We argue that in the mirror model suggested recently to explain the neutrino anomalies, the mirror baryons being 15-20 times heavier than familiar baryons, can play the role of the cold dark matter and provide reasonable explanation of all three above properties without extra assumptions.Comment: Latex, 10 pages; Invited talk presented in PASCOS99 workshop, held in Lake Tahoe, Dec. 1999 and DM2000 workshop held in Los Angeles, February, 200

Mid-infrared optical properties of non-magnetic-metal/CoFeB/MgO heterostructures

We report on the optical characterization of non-magnetic metal/ferromagnetic (Co$_{20}$Fe$_{60}$B$_{20}$)/MgO heterostructures and interfaces by using mid infrared spectroscopic ellipsometry at room temperature. We extracted for the mid-infrared range the dielectric function of Co$_{20}$Fe$_{60}$B$_{20}$, that is lacking in literature, from a multisample analysis. From the optical modelling of the heterostructures we detected and determined the dielectric tensor properties of a two-dimensional gas (2DEG) forming at the non-magnetic metal and the CoFeB interface. These properties comprise independent Drude parameters for the in-plane and out-of plane tensor components, with the latter having an epsilon-near-zero frequency within our working spectral range. A feature assigned to spin-orbit coupling (SOC) is identified. Furthermore, it is found that both, the interfacial properties, 2DEG Drude parameters and SOC strength, and the apparent dielectric function of the MgO layer depend on the type of the underlying nonmagnetic metal, namely, Pt, W, or Cu. The results reported here should be useful in tailoring novel phenomena in such types of heterostructures by assessing their optical response noninvasively, complementing existing characterization tools such as angle-resolved photoemission spectroscopy, and those related to electron/spin transport.Comment: 11 pages, 7 figures. See supplemental material in 10.1088/1361-6463/acd00f/met

APPLICATIONS OF THREE-DIMENSIONAL SCANNING TECHNOLOGY FOR THE COORDINATION OF HISTORICAL MONUMENTS OF NATIONAL INSTITUTE OF ARCHAEOLOGY AND HISTORY (INAH) IN MEXICO CITY. (2009 AND 2010)

[EN] The National Institute of Archaeology and History manages the documentation and preservation of the patrimony of Mexico, a country with an area of ??1.959.000 square kilometers, which is almost four times the size of Spain. To attend on all this patrimony, INAH has several departments. The National Coordination of Historical Monuments manages the monuments and architecture built from the colonial era. Inside the Coordination, the Technical Support Division manages the teams and the tools necessary for the survey[ES] El Instituto Nacional de Arqueología e Historia gestiona la documentación y conservación del patrimonio de México un país con una extensión de 1.959000 kilómetros cuadrados, que casi cuadriplica la extensión de España. Para atender todo este Patrimonio el INAH cuenta con diversos departamentos. La Coordinación Nacional de Monumentos Históricos gestiona los monumentos y arquitecturas construidos a partir de la época virreinal. Dentro de la Coordinación, la Dirección de Apoyo Técnico gestiona los equipos e instrumentos necesarios para el levantamiento.Navarro Esteve, P.; Herráez Boquera, J.; Mora Flores, Á.; Barros E Costa, H.; Denia Ríos, JL. (2011). APLICACIONES DE LA TECNOLOGÍA DE DIGITALIZACIÓN TRIDIMENSIONAL POR LA COORDINACIÓN DE MONUMENTOS HISTÓRICOS DEL INSTITUTO NACIONAL DE ARQUEOLOGÍA E HISTORIA (INAH) EN MÉXICO DF. (2009 Y 2010). EGA. Revista de Expresión Gráfica Arquitectónica. 16(17). doi:10.4995/ega.2011.882SWORD4253161

Impact of Supernova feedback on the Tully-Fisher relation

Recent observational results found a bend in the Tully-Fisher Relation in such a way that low mass systems lay below the linear relation described by more massive galaxies. We intend to investigate the origin of the observed features in the stellar and baryonic Tully-Fisher relations and analyse the role played by galactic outflows on their determination. Cosmological hydrodynamical simulations which include Supernova feedback were performed in order to follow the dynamical evolution of galaxies. We found that Supernova feedback is a fundamental process in order to reproduce the observed trends in the stellar Tully-Fisher relation. Simulated slow rotating systems tend to have lower stellar masses than those predicted by the linear fit to the massive end of the relation, consistently with observations. This feature is not present if Supernova feedback is turned off. In the case of the baryonic Tully-Fisher relation, we also detect a weaker tendency for smaller systems to lie below the linear relation described by larger ones. This behaviour arises as a result of the more efficient action of Supernovae in the regulation of the star formation process and in the triggering of powerful galactic outflows in shallower potential wells which may heat up and/or expel part of the gas reservoir.Comment: 10 pages, 9 figures, accepted for publication in A&

The dark matter content of the blue compact dwarf NGC 2915

NGC 2915 is a nearby blue compact dwarf with the HI properties of a late-type spiral. Its large, rotating HI disk (extending out to R ~ 22 B-band scale lengths) and apparent lack of stars in the outer HI disk make it a useful candidate for dark matter studies. New HI synthesis observations of NGC 2915 have been obtained using the Australian Telescope Compact Array. These data are combined with high-quality 3.6 $\mu$m imaging from the Spitzer Infrared Nearby Galaxies Survey. The central regions of the HI disk are shown to consist of two distinct HI concentrations with significantly non-Gaussian line profiles. We fit a tilted ring model to the HI velocity field to derive a rotation curve. This is used as input for mass models that determine the contributions from the stellar and gas disks as well as the dark matter halo. The galaxy is dark-matter-dominated at nearly all radii. At the last measured point of the rotation curve, the total mass to blue light ratio is ~ 140 times solar, making NGC 2915 one of the darkest galaxies known. We show that the stellar disk cannot account for the steeply-rising portion of the observed rotation curve. The best-fitting dark matter halo is a pseudo-isothermal sphere with a core density $\rho_0\sim 0.17 \pm 0.03$ \msun pc$^{-3}$ and a core radius $r_c\sim 0.9 \pm 0.1$ kpc.Comment: MNRAS in press. 17 pages, 15 figure

531 new spectroscopic redshifts from the CDFS and a test on the cosmological relevance of the GOODS-South field

(Abbrev.) This paper prepares a series of papers analysing the Intermediate MAss Galaxy Evolution Sequence (IMAGES) up to z=1. Intermediate mass galaxies (MJ <=-20.3) are selected from the Chandra Deep Field South (CDFS) for which we identify a serious lack of spectroscopically determined redshifts..... We have spectroscopically identified 691 objects including 580 gal., 7 QSOs, and 104 stars. This study provides 531 new redshifts in the CDFS. It confirms the presence of several large scale structures in the CDFS. To test the impact of these structures in the GOODS-South field, we ... compare the evolution of rest-frame U, B, V and K galaxy luminosity densities to that derived from the CFRS. The CDFS field shows a significant excess of luminosity densities in the z=0.5-0.75 range, which increases with the wavelength, reaching up to 0.5 dex at 2.1 um. Stellar mass and specific star formation evolutions might be significantly affected by the presence of the peculiar large scale structures at z= 0.668 and at z= 0.735, that contain a significant excess of evolved, massive galaxies when compared to other fields. This leads to a clear warning to results based on the CDFS/GOODS South fields, especially those related to the evolution of red luminosity densities, i.e. stellar mass density and specific star formation rate. Photometric redshift techniques, when applied to that field, are producing quantities which are apparently less affected by cosmic variance (0.25 dex at 2.1 um), however at the cost of the difficulty in disentangling between evolutionary and cosmic variance effects.Comment: Accepted for publication in A&A, 19 pages, 13 figure

Unitarity Bounds and the Cuspy Halo Problem

Conventional Cold Dark Matter cosmological models predict small scale structures, such as cuspy halos, which are in apparent conflict with observations. Several alternative scenarios based on modifying fundamental properties of the dark matter have been proposed. We show that general principles of quantum mechanics, in particular unitarity, imply interesting constraints on two proposals: collisional dark matter proposed by Spergel & Steinhardt, and strongly annihilating dark matter proposed by Kaplinghat, Knox & Turner. Efficient scattering required in both implies m < 12 GeV and m < 25 GeV respectively. The same arguments show that the strong annihilation in the second scenario implies the presence of significant elastic scattering, particularly for large enough masses. Recently, a variant of the collisional scenario has been advocated to satisfy simultaneously constraints from dwarf galaxies to clusters, with a cross section that scales inversely with velocity. We show that this scenario likely involves super-elastic processes, and the associated kinetic energy change must be taken into account when making predictions. Exceptions and implications for experimental searches are discussed.Comment: 4 pages, references adde

Gene discovery for facioscapulohumeral muscular dystrophy by machine learning techniques

Facioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disorder that shows a preference for the facial, shoulder and upper arm muscles. FSHD affects about one in 20-400,000 people, and no effective therapeutic strategies are known to halt disease progression or reverse muscle weakness or atrophy. Many genes may be incorrectly regulated in affected muscle tissue, but the mechanisms responsible for the progressive muscle weakness remain largely unknown. Although machine learning (ML) has made significant inroads in biomedical disciplines such as cancer research, no reports have yet addressed FSHD analysis using ML techniques. This study explores a specific FSHD data set from a ML perspective. We report results showing a very promising small group of genes that clearly separates FSHD samples from healthy samples. In addition to numerical prediction figures, we show data visualizations and biological evidence illustrating the potential usefulness of these results.Peer ReviewedPostprint (published version