Browsing by Subject "cosmological parameters from LSS"

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  • Rasanen, Syksy (2014)
  • Montanari, Francesco; Räsänen, Syksy (2017)
    If the FRW metric is a good approximation on large scales, then the distance and the expansion rate, as well different notions of distance, satisfy certain consistency conditions. We fit the JLA SNIa distance data to determine the expected amplitude of the violation of these conditions if accelerated expansion is due to backreaction. Adding cosmic clock and BAO expansion rate data, we also model-independently determine the current observational limits on such violation. We find that the predicted maximum backreaction amplitude vertical bar k(H)vertical bar less than or similar to 1 (95% C.I.) is of the same order as the current observational constraints vertical bar k(H)vertical bar less than or similar to 1, the precise numbers depending on the adopted fitting method (polynomials or splines) and stellar population evolution model. We also find that constraints on the value of Ho determined from expansion rate data are sensitive to the stellar evolution model. We forecast constraints from projected LSST+Euclid-like SNIa plus Euclid galaxy differential age data. We find improvement by factor of 6 for the backreaction case and 3 for the model-independent case, probing an interesting region of possible signatures.
  • Renk, Janina; Zumalacarregui, Miguel; Montanari, Francesco; Barreira, Alexandre (2017)
    Cosmological models with Galileon gravity are an alternative to the standard ACDM paradigm with testable predictions at the level of its self-accelerating solutions for the expansion history, as well as large-scale structure formation. Here, we place constraints on the full parameter space of these models using data from the cosmic microwave background (CMB) (including lensing), baryonic acoustic oscillations (BAO) and the Integrated Sachs Wolfe (ISW) effect. We pay special attention to the ISW effect for which we use the cross spectra, C-l(Tg), of CMB temperature maps and foreground galaxies from the WISE survey. The sign of C-l(Tg) is set by the time evolution of the lensing potential in the redshift range of the galaxy sample: it is positive if the potential decays (like in ACDM), negative if it deepens. We constrain three subsets of Galileon gravity separately known as the Cubic, Quartic and Quintic Galileons. The cubic Galileon model predicts a negative C-l(Tg) and exhibits a 7.8 sigma tension with the data, which effectively rules it out. For the quartic and quintic models the ISW data also rule out a significant portion of the parameter space but permit regions where the goodness-of-fit is comparable to ACDM. The data prefers a non zero sum of the neutrino masses (Sigma m(v) approximate to 0.5eV) with similar to 5 sigma significance in these models. The best-fitting models have values of Ho consistent with local determinations, thereby avoiding the tension that exists in ACDM. We also identify and discuss a similar to 2 sigma tension that Galileon gravity exhibits with recent BAO measurements. Our analysis shows overall that Galileon cosmologies cannot be ruled out by current data but future lensing, BAO and ISW data hold strong potential to do so.