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These are just rough notes - feel free to correct them, add links, etc. from the Benasque, Pyrenees (mountains on spanish/french border) "Modern Cosmology", 27 July - 14 August 2008 meeting initial participant list. These are not official proceedings. The speakers might even disagree that they said anything even vaguely related to what are in these online notes! Don't say you weren't warned.

Dominik Schwarz - the averaging problem ArXiv:0710.5073

  • compare Hubble scale and comoving distances corresponding to 180deg and 60deg as a function of z - coincidence at around z ~ 1 or so ?
  • BAO and SNeIa are local - SNeIa in the sense that without the z < 0.2 info the dataset loses a lot of its constraining power
  • WMAP alone doesn't give \Omega_\Lambda > 0
  • volume averaging affects power spectrum P(k) !
  • averaging time is over time cone volume, not comoving volume?
  • "synchronous coordinates"
  • can set k_D=0 in the effective Friedmann equation
  • Li & Schwarz 2007: ArXiv:0710.5073
    • r < 30 Mpc @z=0 \Rightarrow | \frac{Q}{4\pi G <\rho>}  \le \sim 0.1, also \propto P_\xi
    • curvature corrections \propto \sqrt{P_\xi} less than 10% for r < 80 Mpc
    • Eq. (15) of 0710.5073 - 10% level at about 50Mpc, so above this the effects are relatively small
    • Fig. 2: this inhomogeneous modelling correctly fits the growth of the variance with z in the Freedman et al 2001 H_0 set of estimates, while variance calculated for a homogeneous model underestimates the variance
    • P_\xi is the "peculiar gravitational potential", i.e. initial power spectrum, it does not have the radiation-matter turn over
    • idea: this method should be used when modelling H_0 in general, for the regions below about 150 Mpc
    • idea: some work done in this direction - consider how H_0 varies in different directions and model this inhomogeneously

-- BoudRoukema - 29 Jul 2008
Topic revision: r2 - 29 Jul 2008, BoudRoukema
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