18,672 research outputs found

    Accessing the Acceleration of the Universe with Sunyaev-Zel'dovich and X-ray Data from Galaxy Clusters

    Full text link
    By using exclusively the Sunyaev-Zel'dovich effect and X-ray surface brightness data from 25 galaxy clusters in the redshift range 0.023< z < 0.784 we access cosmic acceleration employing a kinematic description. Such result is fully independent on the validity of any metric gravity theory, the possible matter-energy contents filling the Universe, as well as on the SNe Ia Hubble diagram.Comment: 3 pages, 4 figures, To appear in the Proceedings of the Twelfth Marcel Grossmann Meeting on General Relativit

    Are Galaxy Clusters Suggesting an Accelerating Universe?

    Full text link
    The present cosmic accelerating stage is discussed through a new kinematic method based on the Sunyaev- Zel'dovich effect (SZE) and X-ray surface brightness data from galaxy clusters. By using the SZE/X-ray data from 38 galaxy clusters in the redshift range 0.14≤z≤0.890.14 \leq z \leq 0.89 [Bonamente et al., Astrop. J. {\bf 647}, 25 (2006)] it is found that the present Universe is accelerating and that the transition from an earlier decelerating to a late time accelerating regime is relatively recent. The ability of the ongoing Planck satellite mission to obtain tighter constraints on the expansion history through SZE/X-ray angular diameters is also discussed. Our results are fully independent on the validity of any metric gravity theory, the possible matter- energy contents filling the Universe, as well as on the SNe Ia Hubble diagram from which the presenting accelerating stage was inferred.Comment: 6 pages, 6 figures, AIP Conf. Proc. Invisible Universe: Proceedings of the Conferenc

    Manejo integrado da pinta-preta do mamoeiro no Ceará.

    Get PDF
    bitstream/item/80199/1/Pinta-Preta68.pd

    Can Old Galaxies at High Redshifts and Baryon Acoustic Oscillations Constrain H_0?

    Full text link
    A new age-redshift test is proposed in order to constrain H0H_0 with basis on the existence of old high redshift galaxies (OHRG). As should be expected, the estimates of H0H_0 based on the OHRG are heavily dependent on the cosmological description. In the flat concordance model (Λ\LambdaCDM), for example, the value of H0H_0 depends on the mass density parameter ΩM=1−ΩΛ\Omega_M=1 - \Omega_{\Lambda}. Such a degeneracy can be broken trough a joint analysis involving the OHRG and baryon acoustic oscillation (BAO) signature. In the framework of the ΛCDM\Lambda CDM model our joint analysis yields a value of H_0=71^{+4}_{-4}\kms Mpc−1^{-1} (1σ1\sigma) with the best fit density parameter ΩM=0.27±0.03\Omega_M=0.27\pm0.03. Such results are in good agreement with independent studies from the {\it{Hubble Space Telescope}} key project and the recent estimates of WMAP, thereby suggesting that the combination of these two independent phenomena provides an interesting method to constrain the Hubble constant.Comment: 16 pages, 6 figures, 1 tabl

    Monitoramento, sanitização e controle químico no manejo da mancha de corinespora do mamoeiro.

    Get PDF
    bitstream/item/80202/1/Mancha-de-CorynesporadoMamoeiro69.pd

    Parameterized Complexity of Equitable Coloring

    Full text link
    A graph on nn vertices is equitably kk-colorable if it is kk-colorable and every color is used either ⌊n/k⌋\left\lfloor n/k \right\rfloor or ⌈n/k⌉\left\lceil n/k \right\rceil times. Such a problem appears to be considerably harder than vertex coloring, being NP-Complete\mathsf{NP\text{-}Complete} even for cographs and interval graphs. In this work, we prove that it is W[1]-Hard\mathsf{W[1]\text{-}Hard} for block graphs and for disjoint union of split graphs when parameterized by the number of colors; and W[1]-Hard\mathsf{W[1]\text{-}Hard} for K1,4K_{1,4}-free interval graphs when parameterized by treewidth, number of colors and maximum degree, generalizing a result by Fellows et al. (2014) through a much simpler reduction. Using a previous result due to Dominique de Werra (1985), we establish a dichotomy for the complexity of equitable coloring of chordal graphs based on the size of the largest induced star. Finally, we show that \textsc{equitable coloring} is FPT\mathsf{FPT} when parameterized by the treewidth of the complement graph
    • …
    corecore