### Cosmology without cosmic variance

The growth of structures in the Universe is described by a function G that is predicted by the combination of the expansion history of the Universe and the laws of gravity within it. We examine the improvements in constraints on G that are available from the combination of a large-scale galaxy redshift survey with a weak gravitational lensing survey of background sources. We describe a new combination of such observations that in principle this yields a measure of the growth rate that is free of sample variance, i.e. the uncertainty in G can be reduced without bound by increasing the number of redshifts obtained within a finite survey volume. The addition of background weak lensing data to a redshift survey increases information on G by an amount equivalent to a 10-fold increase in the volume of a standard redshift-space distortion measurement - if the lensing signal can be measured to sub-per cent accuracy. This argues that a combined lensing and redshift survey over a common low-redshift volume of the Universe is a more powerful test of general relativity than an isolated redshift survey over larger volume at high redshift, especially as surveys begin to cover most of the available sky.

- Publication Date:

- Grant/Contract Number:
- FG02-95ER40893

- Type:
- Accepted Manuscript

- Journal Name:
- Monthly Notices of the Royal Astronomical Society

- Additional Journal Information:
- Journal Volume: 416; Journal Issue: 4; Journal ID: ISSN 0035-8711

- Publisher:
- Royal Astronomical Society

- Research Org:
- Univ. of Pennsylvania, Philadelphia, PA (United States)

- Sponsoring Org:
- USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTRONOMY AND ASTROPHYSICS; linear growth factor G; gravitational lensing; statistical; large-scale structure of universe

- OSTI Identifier:
- 1203601

```
Bernstein, Gary M., and Cai, Yan -Chuan.
```*Cosmology without cosmic variance*. United States: N. p.,
Web. doi:10.1111/j.1365-2966.2011.19249.x.

```
Bernstein, Gary M., & Cai, Yan -Chuan.
```*Cosmology without cosmic variance*. United States. doi:10.1111/j.1365-2966.2011.19249.x.

```
Bernstein, Gary M., and Cai, Yan -Chuan. 2011.
"Cosmology without cosmic variance". United States.
doi:10.1111/j.1365-2966.2011.19249.x. https://www.osti.gov/servlets/purl/1203601.
```

```
@article{osti_1203601,
```

title = {Cosmology without cosmic variance},

author = {Bernstein, Gary M. and Cai, Yan -Chuan},

abstractNote = {The growth of structures in the Universe is described by a function G that is predicted by the combination of the expansion history of the Universe and the laws of gravity within it. We examine the improvements in constraints on G that are available from the combination of a large-scale galaxy redshift survey with a weak gravitational lensing survey of background sources. We describe a new combination of such observations that in principle this yields a measure of the growth rate that is free of sample variance, i.e. the uncertainty in G can be reduced without bound by increasing the number of redshifts obtained within a finite survey volume. The addition of background weak lensing data to a redshift survey increases information on G by an amount equivalent to a 10-fold increase in the volume of a standard redshift-space distortion measurement - if the lensing signal can be measured to sub-per cent accuracy. This argues that a combined lensing and redshift survey over a common low-redshift volume of the Universe is a more powerful test of general relativity than an isolated redshift survey over larger volume at high redshift, especially as surveys begin to cover most of the available sky.},

doi = {10.1111/j.1365-2966.2011.19249.x},

journal = {Monthly Notices of the Royal Astronomical Society},

number = 4,

volume = 416,

place = {United States},

year = {2011},

month = {10}

}