We analyse CMB data in a manner which is as independent as possible of the model of late-time cosmology. We encode the effects of late-time cosmology into a single parameter which determines the distance to the last scattering surface. We exclude low multipoles ℓ < 40 from the analysis. We consider the WMAP5 and ACBAR data. We obtain the cosmological parameters 100ω b = 2.13 ± 0.05, ω c = 0.124 ± 0.007, n s = 0.93 ± 0.02 and θ A = 0.593 • ± 0.001 • (68% C.L.). The last number is the angular scale subtended by the sound horizon at decoupling. There is a systematic shift in the parameters as more low ℓ data are omitted, towards smaller values of ω b and n s and larger values of ω c . The scale θ A remains stable and very well determined. 18 A. The scale parameter approximation 19 B. Reionization 23 ℓ min 2 20 40 60 100ω b 2.21 +0.05 −0.05 2.19 +0.05 −0.05 2.18 +0.07 −0.07 2.15 +0.08 −0.08 ω c 0.113 +0.005 −0.005 0.115 +0.006 −0.006 0.118 +0.
We study a homogeneous and nearly-isotropic Universe permeated by a homogeneous magnetic field. Together with an isotropic fluid, the homogeneous magnetic field, which is the primary source of anisotropy, leads to a plane-symmetric Bianchi I model of the Universe. However, when free-streaming relativistic particles are present, they generate an anisotropic pressure which counteracts the one from the magnetic field such that the Universe becomes isotropized. We show that due to this effect, the CMB temperature anisotropy from a homogeneous magnetic field is significantly suppressed if the the neutrino masses are smaller than 0.3 eV.
We study the distance-redshift relation in a universe filled with 'walls' of pressure-less dust separated by under dense regions. We show that as long as the density contrast of the walls is small, or the diameter of the under dense regions is much smaller than the Hubble scale, the distance-redshift relation remains close to what is obtained in a Friedmann universe. However, when arbitrary density contrasts are allowed, every prescribed distance-redshift relation can be reproduced with such models.
Abstract. If our Universe is a 3 + 1 brane in a warped 4 + 1 dimensional bulk so that its expansion can be understood as the motion of the brane in the bulk, the time dependence of the boundary conditions for arbitrary bulk fields can lead to particle creation via the dynamical Casimir effect. In this talk I report results for the simplest such scenario, when the only particle in the bulk is the graviton and the bulk is the 5 dimensional anti-de Sitter spacetime.
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