18,672 research outputs found
Accessing the Acceleration of the Universe with Sunyaev-Zel'dovich and X-ray Data from Galaxy Clusters
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?
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 [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.
bitstream/item/80199/1/Pinta-Preta68.pd
Can Old Galaxies at High Redshifts and Baryon Acoustic Oscillations Constrain H_0?
A new age-redshift test is proposed in order to constrain with basis on
the existence of old high redshift galaxies (OHRG). As should be expected, the
estimates of based on the OHRG are heavily dependent on the cosmological
description. In the flat concordance model (CDM), for example, the
value of depends on the mass density parameter . Such a degeneracy can be broken trough a joint analysis
involving the OHRG and baryon acoustic oscillation (BAO) signature. In the
framework of the model our joint analysis yields a value of
H_0=71^{+4}_{-4}\kms Mpc () with the best fit density
parameter . 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 quÃmico no manejo da mancha de corinespora do mamoeiro.
bitstream/item/80202/1/Mancha-de-CorynesporadoMamoeiro69.pd
Parameterized Complexity of Equitable Coloring
A graph on vertices is equitably -colorable if it is -colorable and
every color is used either or times.
Such a problem appears to be considerably harder than vertex coloring, being
even for cographs and interval graphs.
In this work, we prove that it is for block
graphs and for disjoint union of split graphs when parameterized by the number
of colors; and for -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 when
parameterized by the treewidth of the complement graph
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