# Presentation: 034873

## Yi Mao, MIT

- Collaborators: Max Tegmark, Alan Guth, Matias Zaldarriaga, Matt McQuinn, Oliver Zahn, Tom Faulkner, Ted Bunn, Serkan Cabi

- Constraining cosmological and gravitational parameters with upcoming astrophysical data

## Outline

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Overview: cosmological probes
- 21cm-tomography
- Overview: testing gravity
- Testing f(R) gravity
- Testing torsion gravity
- Outlook

## What do we learn in cosmology?

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## 0th order:

- <date/time>

- Expansion

- a(t)
- k

- H(z)

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Distant light is {

- Distant light is {

- dimmed

- redshifted

- distance Vs. z

- H(z)

## 1st order:

- <date/time>

- Clustering

- C*l*, P(k), ...

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Slide 7

## But the best is yet  

- <date/time>

- But the best is yet
- to come

- Precision CMB (polarization, small scales),
- precision lensing
- ......

- and *21cm tomography*

- Yi Mao
- Fermilab seminar
- January 23, 2008

## 21cm

- tomography

## Murchison Widefield Array (MWA)

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Located in western Australia
- 500 antennas; array diameters 1500m;
- Measures z=6~12

## Other arrays

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Square Kilometre Array (SKA)
- Low Frequency Array (LOFAR)
- 21cm Array (21CMA)

## 21cm line from the Epoch of Reionization

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Slide 13

## 21cm Power spectrum

- Yi Mao
- Fermilab seminar
- January 23, 2008

- 21cm power spectrum is _not_ isotropic because of redshift space distortion!

## How accurately can 21cm tomography constrain cosmological parameters?

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Yi Mao

- Fermilab seminar
- January 23, 2008

## YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

- Yi Mao
- Fermilab seminar
- January 23, 2008

*K*

## YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

- Yi Mao
- Fermilab seminar
- January 23, 2008

*K*

## Ionization power spectrum modeling

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## OPT

- Yi Mao
- Fermilab seminar
- January 23, 2008

## PESS

- Yi Mao
- Fermilab seminar
- January 23, 2008

## MID

- Yi Mao
- Fermilab seminar
- January 23, 2008

- YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

## YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

- Yi Mao
- Fermilab seminar
- January 23, 2008

*K*

## Optimal array configuration

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## LOFAR

- Yi Mao
- Fermilab seminar
- January 23, 2008

- MWA

- SKA

- MID

- OPT

- Size of compact core

- Size of total inner core

- YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

## MWA in OPT model

- Size of compact core

- Size of total inner core

- YM, Tegmark, McQuinn, Zaldarriaga & Zahn (2008)

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Future: 3D neutral hydrogen maps?

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Testing gravity in a general framework

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Generalize PPN

- A general geometry is determined by metric (g) and connection (), both independent of each other.
- Three quantities characterize the departure from Minkowski spacetime:

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Generalized geometry family tree

## Constraining torsion

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Parametrization of torsion around Earth

## Constraining torsion with GPB

## Constraining torsion with GPB

- YM, Tegmark, Guth, Cabi (2006)

## Constraining f(R) gravity

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## Solar system constraints on f(R) Chameleon  

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Solar system constraints on f(R) Chameleon

- Faulkner, Tegmark, Bunn and YM (2007)

## Constraints on cubic f(R) model

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Faulkner, Tegmark, Bunn and YM (2007)

## Outlook

- Yi Mao
- Fermilab seminar
- January 23, 2008

- 3D HI mapping: direct view into the dark ages, precision constraints on cosmological parameters
- Better understanding of the Epoch of Reionization
- New tests of Einstein gravity on scales from the solar system to the cosmos
- Common question for cosmology and gravitation:
-        Dark energy = cosmological constant or modified gravity?
-        Dark matter = new particles or TeVeS/MOND?
-        Can GR (and standard cosmological model) be further tested?

## <footer>

- <date/time>

- Yi Mao
- Fermilab seminar
- January 23, 2008

## 21cm line

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Spin temperature                                          , where
- Emission if Ts > Tcmb; absorption if Ts < Tcmb
- Saturated when Ts >> Tcmb; arbitrarily large when Ts << Tcmb
- The last factor makes the anisotropy!

## Ts couplings

- Yi Mao
- Fermilab seminar
- January 23, 2008

- Ts couplings

- Absorption of CMB photons and stimulated emission
- Collisions with H, e, p: Ts  Tk
- Scattering of UV photons( the Wouthuysen-Field Effect): Ts  TLya

- Furlanetto, Oh & Briggs 2006

## Thermal histroy of IGM

- Yi Mao
- Fermilab seminar
- January 23, 2008

- zdec~150: compton heating.
-                      Tk = Tcmb before zdec; Tk~(1+z)2 after.
- Z1: Ts = Tk before z1; Ts  Tcmb after.
- Zh: IGM Tk > Tcmb.
- Zc: Wouthuysen-Field Effect couples Ts = Tk again.
- Zr: reionization.