Article

# Second Order Gravitational Effects on CMB Temperature Anisotropy in Lambda dominated flat universes

01/2008;
Source: arXiv

ABSTRACT We study second order gravitational effects of local inhomogeneities on the cosmic microwave background radiation in flat universes with matter and a cosmological constant $\Lambda$. We find that the general relativistic correction to the Newtonian approximation is negligible at second order provided that the size of the inhomogeneous region is sufficiently smaller than the horizon scale. For a spherically symmetric top-hat type quasi-linear perturbation, the first order temperature fluctuation corresponding to the linear integrated Sachs-Wolfe (ISW) effect is enhanced(suppressed) by the second order one for a compensated void(lump). As a function of redshift of the local inhomogeneity, the second order temperature fluctuations due to evolution of the gravitational potential have a peak before the matter-$\Lambda$ equality epoch for a fixed comoving size and a density contrast. The second order gravitational effects from local quasi-linear inhomogeneities at a redshift z~1 may significantly affect the cosmic microwave background.

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### Keywords

compensated void(lump)

cosmic microwave background

cosmological constant $\Lambda$

first order temperature fluctuation corresponding

fixed comoving size

flat universes

general relativistic correction

gravitational potential

inhomogeneous region

ISW

local inhomogeneity

local quasi-linear inhomogeneities

matter-$\Lambda$ equality epoch

spherically symmetric top-hat type quasi-linear perturbation