Large-scale homogeneity vs. small- scale inhomogeneity: testing ...

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• Cosmological principle: Universe is homogeneous and isotropic Large-scale Cosmic Homogeneity − Homogeneous: different regions of the Universe have the same mean density − Isotropic: looks the same in all directions • Allows use of Friedmann-Robertson- Walker (FRW) spacetime metric • Need FRW to convert redshifts to distances, via Friedmann eqn: 2 H 2 H0 = ! Ra"4 + ! Ma "3 + ! ka "2 + ! # 01/18/2013 Morag I. Scrimgeour Springel et al. (2005) 4
Inhomogeneity: alternative to Dark • Is ‘perturbed FRW’ a valid description? • Large inhomogeneities → breakdown of FRW 01/18/2013 − Light paths distorted: distances inferred from redshifts are wrong (e.g. Wiltshire 2010) − “Averaging problem” and backreaction: different-density regions evolve differently, can have global accelerated expansion without Dark Energy (e.g. Buchert 2007, Li & Schwarz 2009, Räsänen 2011) − Void models, e.g. Lemaître- Tolman-Bondi model Energy? Image: hubblesite.org Morag I. Scrimgeour 5
Page 1 and 2: ICRAR is a partnership between the
Page 3: 01/18/2013 Testing large-scale cosm
Page 7 and 8: • So far, results are conflicting
Page 9 and 10: Fractal (correlation) dimension D 2
Page 11 and 12: 01/18/2013 Selection Function Corre
Page 13 and 14: • In ΛCDM expect: − Small scal
Page 15 and 16: How do we define the “homogeneity
Page 17 and 18: 01/18/2013 0.3
Page 19 and 20: 01/18/2013 0.7
Page 21 and 22: 01/18/2013 ΛCDM D 2(r) model: effe
Page 23 and 24: Scrimgeour et al. (2012) 01/18/2013
Page 25 and 26: • WiggleZ measurement of homogene
Page 27 and 28: 01/18/2013 What are peculiar veloci
Page 29 and 30: 01/18/2013 Large-scale Dark Matter
Page 32 and 33: • Nature of dark energy − Expan
Page 34 and 35: • Nature of dark energy Peculiar
Page 36 and 37: 01/18/2013 • Bulk Flow / dipole (
Page 38 and 39: Bulk flows and dark flows: a proble
Page 40 and 41: 01/18/2013 Conflicting σ 8 constra
Page 42 and 43: 01/18/2013 Several potential system
Page 44 and 45: 6dFGS Peculiar Velocities • Spect
Page 46 and 47: ~500 Type Ia SNe over 5 years (Scri
Page 48 and 49: 01/18/2013 Bulk flow distribution
Page 50 and 51: 01/18/2013 True bulk flow The ‘re
Page 52 and 53: 01/18/2013 True bulk flow Observed
Page 54 and 55:
01/18/2013 Bulk Flow Systematics fr
Page 56 and 57:
N(z) 01/18/2013 4000 3500 3000 2500
Page 58:
Homogeneity in the WiggleZ Survey S
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Large-scale homogeneity vs. small- scale inhomogeneity: testing ...

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