1,720,967 research outputs found
Test of modified Newtonian dynamics with recent Boomerang data
No full textPurely baryonic dark matter dominated models like modified Newtonian dynamics (MOND) based on modification of Newtonian gravity have been successful in reproducing some dynamical properties of galaxies. More recently, a relativistic formulation of MOND proposed by Bekenstein seems to agree with cosmological large scale structure formation. In this work, we revise the agreement of MOND with observations in light of the new results on the cosmic microwave anisotropies provided by the 2003 flight of Boomerang. The measurements of the height of the third acoustic peak, provided by several small scale CMB experiments have reached enough sensitivity to severely constrain models without cold dark matter. Assuming that acoustic peak structure in the CMB is unchanged and that local measurements of the Hubble constant can be applied, we find that the cold dark matter is strongly favored with Bayesian probability ratio of about one in two hundred
Improved cosmological bound on the thermal axion mass
No full textRelic thermal axions could play the role of an extra hot dark matter component in cosmological structure formation theories. By combining the most recent observational data we improve previous cosmological bounds on the axion mass m(a) in the so-called hadronic axion window. We obtain a limit on the axion mass m(a)< 0.42 eV at the 95% C.L. (m(a)< 0.72 eV at the 99% C.L.). A novel aspect of the analysis presented here is the inclusion of massive neutrinos and how they may affect the bound on the axion mass. If neutrino masses belong to an inverted hierarchy scheme, for example, the above constraint is improved to m(a)< 0.38 eV at the 95% C.L. (m(a)< 0.67 eV at the 99% C.L.). Future data from experiments as CAST will provide a direct test of the cosmological bound
Is cosmology compatible with sterile neutrinos?
Full text linkBy combining data from cosmic microwave background experiments (including the recent WMAP third year results), large scale structure, and Lyman-alpha forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless+1 massive neutrino case, we bound the mass of the sterile neutrino to m(s) 1 or < 0.05 eV, the cosmological energy density in sterile neutrinos is always constrained to be omega(nu)< 0.003 at 95% C.L., but for a mass of similar to 0.25 eV, omega(nu) can be as large as 0.01
Inflation and WMAP three year data: Features are still present
No full textThe new 3 year WMAP data seem to confirm the presence of nonstandard large scale features in the cosmic microwave anisotropy power spectrum. While these features may hint at uncorrected experimental systematics, it is also possible to generate, in a cosmological way, oscillations on large angular scales by introducing a sharp step in the inflaton potential. Using current cosmological data, we derive constraints on the position, magnitude and gradient of a possible step. We show that a step in the inflaton potential, while strongly constrained by current data, is still allowed and may provide an interesting explanation to the currently measured deviations from the standard featureless spectrum. Moreover, we show that inflationary oscillations in the primordial power spectrum can significantly bias parameter estimates from standard ruler methods involving measurements of baryon oscillations
New Constraints on Oscillations in the Primordial Spectrum of Inflationary Perturbations.
No full textWe revisit the problem of constraining steps in the inflationary potential with cosmological data. We argue that a step in the inflationary potential produces qualitatively similar oscillations in the primordial power spectrum, independently of the details of the inflationary model. We propose a phenomenological description of these oscillations and constrain these features using a selection of cosmological data including the baryonic peak data from the correlation function of luminous red galaxies in the Sloan Digital Sky Survey. Our results show that degeneracies of the oscillation with standard cosmological parameters are virtually nonexistent. The inclusion of new data severely tightens the constraints on the parameter space of oscillation parameters with respect to older work. This confirms that extensions to the simplest inflationary models can be successfully constrained using cosmological data
New constraints on neutrino masses from cosmology
Full text linkBy combining data from cosmic microwave background (CMB) experiments (including the recent WMAP third year results), large scale structure (LSS) and Lyman-alpha forest observations, we derive upper limits on the sum of neutrino masses of Sigma m(v) 1 eV or < 0.05 eV the cosmological energy density in sterile neutrinos is always constrained to be omega(nu) < 0.003 at 95% c.l. However, for a sterile neutrino mass of similar to 0.25 eV, omega(nu) can be as large as 0.01. (c) 2006 Elsevier B.V. All rights reserved
Sterile neutrinos in light of recent cosmological and oscillation data: a multi-flavor scheme approach
No full textLight sterile neutrinos might mix with the active ones and be copiously produced in the early Universe. In the present paper, a detailed multi-flavor analysis of sterile neutrino production is performed. Making some justified approximations allows us to consider not only neutrino interactions with the primeval medium and neutrino coherence breaking effects, but also oscillation effects arising from the presence of three light (mostly-active) neutrino states mixed with two heavier (mostly-sterile) states. First, we emphasize the underlying physics via an analytical description of sterile neutrino abundances that is valid for cases with small mixing between active and sterile neutrinos. Then, we study in detail the phenomenology of (3+2) sterile neutrino models in light of short-baseline oscillation data, including the LSND and MiniBooNE results. Finally, by using the information provided by this analysis, we obtain the expected sterile neutrino cosmological abundances and then contrast them with the most recet available data from Cosmic Microwave Background and Large Scale Structure observations. We conclude that (3+2) models are significantly more disfavored by the internal inconsistencies between sterile neutrino interpretations of appearance and disappearance short-baseline data themselves, rather than by the used cosmological data.OM is supported by a Ram´on y Cajal contract from the Spanish Government. SPR is supported by the Portuguese FCT through the projects POCI/FP/81919/2007 and CFTP-FCT UNIT 777, which are partially funded through POCTI (FEDER). SPR is also partially supported by the Spanish Grant FPA2005-01678 of the MCT. MS would like to acknowledge support by the Spanish Ministry of Science and Innovation via a CSIC JAE-DOC contract, and use of the computing cluster of the experimental neutrino group at IFIC for this work.Peer reviewe
CMB lensing constraints on dark energy and modified gravity scenarios
Full text linkWeak gravitational lensing leaves a characteristic imprint on the cosmic microwave background temperature and polarization angular power spectra. Here, we investigate the possible constraints on the integrated lensing potential from future cosmic microwave background angular spectra measurements expected from Planck and EPIC. We find that Planck and EPIC will constrain the amplitude of the integrated projected potential responsible for lensing at 6% and 1% level, respectively, with very little sensitivity to the shape of the lensing potential. We discuss the implications of such a measurement in constraining dark energy and modified gravity scalar-tensor theories. We then discuss the impact of a wrong assumption on the weak lensing potential amplitude on cosmological parameter inference. © 2009 The American Physical Society
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