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Testing Gravity Against Early Time Integrated Sachs-Wolfe Effect

Pengjie Zhang
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Abstract

A generic prediction of general relativity is that the cosmological linear density growth factor $D$ is scale independent. But in general, modified gravities do not preserve this signature. A scale dependent $D$ can cause time variation in gravitational potential at high redshifts and provides a new cosmological test of gravity, through early time integrated Sachs-Wolfe (ISW) effect-large scale structure (LSS) cross correlation. We demonstrate the power of this test for a class of $f(R)$ gravity, with the form $f(R)=-λ_1 H_0^2\exp(-R/λ_2H_0^2)$. Such $f(R)$ gravity, even with degenerate expansion history to $Λ$CDM, can produce detectable ISW effect at $z\ga 3$ and $l\ga 20$. Null-detection of such effect would constrain $λ_2$ to be $λ_2>1000$ at $>95%$ confidence level. On the other hand, robust detection of ISW-LSS cross correlation at high $z$ will severely challenge general relativity.

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Pengjie Zhang. 2006-05-12. Testing Gravity Against Early Time Integrated Sachs-Wolfe Effect. https://doi.org/10.1103/physrevd.73.123504

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