CMB seen through random Swiss Cheese

Abstract

Abstract. We consider a Swiss Cheese model with a random arrangement of Lemaître-Tolman-Bondi holes in ΛCDM cheese. We study two kinds of holes with radius r b = 50 h −1 Mpc, with either an underdense or an overdense centre, called the open and closed case, respectively. We calculate the effect of the holes on the temperature, angular diameter distance and, for the first time in Swiss Cheese models, shear of the CMB. We quantify the systematic shift of the mean and the statistical scatter, and calculate the power spectra.In the open case, the temperature power spectrum is three orders of magnitude below the linear ISW spectrum. It is sensitive to the details of the hole, in the closed case the amplitude is two orders of magnitude smaller. In contrast, the power spectra of the distance and shear are more robust, and agree with perturbation theory and previous Swiss Cheese results. We do not find a statistically significant mean shift in the sky average of the angular diameter distance, and obtain the 95% limit |∆D A /D A | 10 −4 .We consider the argument that areas of spherical surfaces are nearly unaffected by perturbations, which is often invoked in light propagation calculations. The closed case is consistent with this at 1σ, whereas in the open case the probability is only 1.4%.

Light path averages in spacetimes with nonvanishing average spatial curvature

“…In particular, when using different types of averages such as area, angular, source and ensemble averages, certain observables will be unbiased in their mean while observables * sofie.koksbang@helsinki.fi depending non-linearly on these will have small biases. This has been shown with studies based on perturbative expansions [12][13][14][15][16][17][18] and is consistent with findings based on Swiss cheese models and similar [8,[19][20][21][22][23][24][25] and on N-body simulations [6,26].…”

Geodesic-light-cone coordinates and the Bianchi I spacetime

“…Note however that the non-perturbative numerical analysis of light propagation through a random Swiss-cheese model with transparent Lemaître-Tolman-Bondi holes, performed by Lavinto & Räsänen [61], exhibited deviations with respect to this rule.…”

Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology: a review

“…Interestingly, the standard deviation for dispersions ∆µ was found to be 0.004 ≤ σ ∆µ ≤ 0.008, smaller than the intrinsic dispersion of magnitudes of Type Ia supernovae. Lavinto & Räsänen (2015) examined the CMB as seen through random Swiss cheese. Usually, 'closed' holes had been examined, i.e.…”

“…an overdense centre surrounded by an underdensity. Lavinto & Räsänen (2015) examind 'open' holes as well, i.e. an underdense void surrounded by a thin overdense shell.…”

“…Since the relevant angular scales are much larger than those involved in the ZKDR distance, further discussion of CMB anisotropies is beyond the scope of the present work. Lavinto & Räsänen (2015), apart from presenting original results, also gave a good review of this topic and its connection to the ZKDR distance.…”