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SUMMARY:Discovery of a 4-sigma deviation from the Concordance Model of Cos
 mology using the Hubble Diagram of  Quasars. - Elisabeta Lusso (Durham)
DTSTART:20180810T103000Z
DTEND:20180810T113000Z
UID:TALK106615@talks.cam.ac.uk
CONTACT:Martin Haehnelt
DESCRIPTION:The cosmological concordance model (ΛCDM) well accounts for a
  wealth of observations\, from the existence of Cosmic Microwave backgroun
 d (CMB) to the discovery of the accelerated expansion of the universe from
  Type Ia supernovae. Yet\, it assumes a still unknown form of dark energy 
 and matter and some tensions arose recently as\, for instance\, the discov
 ery of a 3.4σ discrepancy between the local (Riess et al. 2016) and Planc
 k (Aghanim et al. 2016) measurement of H0. In addition\, the ΛCDM model i
 s poorly tested in the redshift interval between the farthest observed Typ
 e Ia supernovae (z = 1.4) and that of the CMB (z = 1100). We present new m
 easurements of the expansion rate of the Universe in the redshift range z=
 0.5-5.5 based on a Hubble diagram of quasars. The distance of quasars have
  been estimated from the observed non-linear relation between the X-ray an
 d ultraviolet emission\, following a method developed by our group. The di
 stance-redshift relation of quasars at z < 1.4 is in agreement with that o
 f supernovae and with the concordance model. Nonetheless\, a deviation fro
 m the ΛCDM model emerges at higher redshift\, with a statistical signific
 ance of 4σ. We found that\, if an evolution of the dark energy equation o
 f state is allowed\, our data suggest a dark energy density increasing wit
 h time.\n
LOCATION:Kavli Large Meeting Room\, Kavli Building
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