The scale of cosmic homogeneity as a standard ruler Ntelis, Pierros; Ealet, Anne; Escoffier, Stephanie ...
Journal of Cosmology and Astroparticle Physics,
12/2018, Letnik:
2018, Številka:
12
Journal Article
In this paper, we study the normalised characteristic scale of transition to cosmic homogeneity, \(\mathcal{R}_H/d_V\), as a cosmological probe. We use a compilation of SDSS galaxy samples, ...comprising more than \(10^6\) galaxies in the redshift range \(0.17 \leq z \leq 2.2\) within the largest comoving volume to date, \(\sim 8 h^{-3}\mathrm{Gpc}^3\). We show that these samples can be described by a single bias model as a function of redshift. By combining our measurements with prior Cosmic Microwave Background and Lensing information from the Planck satellite, we constrain the total matter density ratio of the universe, \(\Omega_m = 0.363 \pm 0.025\), and the Dark Energy density ratio, \(\Omega_{\Lambda} = 0.649 \pm 0.021\), improving the values from Planck alone by 31% and 28%, respectively. Our results are compatible with a flat \(\Lambda\)CDM model. These results show the complementarity of the normalised homogeneity scale with other cosmological probes and open new roads to cosmometry.
In this paper, we study the characteristic scale of transition to cosmic homogeneity of the universe, \(\mathcal{R}_H\), as a standard ruler, to constrain cosmological parameters on mock galaxy ...catalogues. We use mock galaxy catalogues that simulate the CMASS galaxy sample of the BOSS survey in the redshift range \(0.43 \leq z \leq 0.7\). In each redshift bin we obtain the homogeneity scale, defined as the scale at which the universe becomes homogeneous to \(1\%\), i.e. \(D_2(\mathcal{R}_H) = 2.97\). With a simple Fisher analysis, we find that the performance of measuring the cosmological parameters with either the position of the BAO peak or the homogeneity scale is comparable. We show that \(\mathcal{R}_H\) has a dependence on the galaxy bias. If the accuracy and precision of this bias is achieved to \(1\%\), as expected for future surveys, then \(\mathcal{R}_H\) is a competitive standard ruler.
Objective To review our clinical T1a renal mass active surveillance (AS) cohort to determine whether renal mass biopsy was associated with maintenance of AS. Materials and Methods From our ...prospectively maintained database we identified patients starting AS from June 2009 to December 2011 who had at least 5 months of radiologic follow-up, unless limited by unexpected death or delayed intervention. The primary outcome was delayed intervention. Clinical, radiologic, and pathologic variables were compared. We constructed Kaplan-Meier survival curves for maintenance of AS. Cox multivariable regression analysis was performed to assess predictors of delayed intervention. Results We identified 118 patients who met criteria for inclusion with a median radiologic follow-up of 29.5 months. The delayed intervention group had greater initial mass size and faster growth rate compared to those who continued AS. Rate of renal mass biopsy was similar between the 2 groups. In the multivariable analysis, size >2 cm (hazard ratio HR 3.65, 95% confidence interval CI 1.28-10.38, P = .015), growth rate (continuous by mm/year: HR 1.26, 95% CI 1.12-1.41, P < .001), but not renal biopsy (HR 1.52, 95% CI 0.70-3.30, P = .29), were associated with increased risk of delayed intervention. Time-to-event curves also showed that size was closely associated with delayed intervention whereas renal mass biopsy was not. Conclusion At our institution, growth rate and initial tumor size appear to be more influential than renal mass biopsy results in determining delayed intervention after a period of AS. Further analysis is required to determine the role of renal biopsy in the management of patients being considered for AS.
We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly\(\alpha\) forests from the completed Sloan Digital Sky Survey (SDSS) lineage of ...experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, \(r_d\), from eight different samples and six measurements of the growth rate parameter, \(f\sigma_8\), from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, \(\Lambda\)CDM model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization the BAO data provide nearly an order of magnitude improvement on curvature constraints. The RSD measurements indicate a growth rate that is consistent with predictions from Planck primary data and with General Relativity. When combining the results of SDSS BAO and RSD with external data, all multiple-parameter extensions remain consistent with a \(\Lambda\)CDM model. Regardless of cosmological model, the precision on \(\Omega_\Lambda\), \(H_0\), and \(\sigma_8\), remains at roughly 1\%, showing changes of less than 0.6\% in the central values between models. The inverse distance ladder measurement under a o\(w_0w_a\)CDM yields \(H_0= 68.20 \pm 0.81 \, \rm km\, s^{-1} Mpc^{-1}\), remaining in tension with several direct determination methods. (abridged)
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