Loading in 5 sec....

Cosmology : a short introductionPowerPoint Presentation

Cosmology : a short introduction

- 94 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' Cosmology : a short introduction' - lee-lewis

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

### Cosmology : a short introduction

### 0. What do we see ?

### 1. How do we understand what we see? full sky

Mathieu Langer

Institut d’Astrophysique Spatiale

Université Paris-Sud XI

Orsay, France

Egyptian School on High Energy Physics

CTP-BUE , Egypt

27 May – 4 June 2009

(depends on wavelength…)

Cosmic Microwave Background (detected 1965, Penzias & Wilson, Nobel prize 1978)

(COBE data, 1996)

What Penzias & Wilson would have seen, had they observed the full sky

The Milky Way

Cosmological interpretation:

Dicke, Peebles, Roll, Wilkinson (1965)

Cosmic Microwave Background full sky(detected 1965, Penzias & Wilson, Nobel prize 1978)

(COBE data, 1996)

CMB : tiny anisotropies full sky

COBE, 1991-1996

First detection of anisotropies

(Nobel prize 2006: Smoot & Mather)

CMB : tiny anisotropies, huge information full sky

-200 µK < ΔT < 200 µK

First fine-resolution full-sky map (0.2 degrees)

WMAP: 2003, 2006, 2008

(Launched June 2001)

…to cosmological parameters and cosmic pies : full sky

Age : 13.7 billion years

Panoramic view of the entire near-infrared sky full sky

Blue : nearest galaxies

Red : most distant (up to ~ 410 Mpc)

Distribution of structure on large scales(2MASS, XSC & PSC)

Notice : full skyisotropy & homogeneity!

Hubble’s law, expansion of the universe full sky

V = H0 D

H0 = 71 ± 4 km/s/Mpc

(from WMAP + Structures)

(Hubble, 1929)

Rem : 1 parsec ~ 3.262 light years ~ 3.1×1013 km

Ambitious cosmology… full sky

Our understanding of the universe… full sky

Cosmological principle full sky

Universe : spatially homogeneous & isotropiceverywhere

Applies to regions unreachable by observation

Copernican principle

Our place is not special observations are the same for any observer

Isotropy + Copernicus homogeneity

Applies to observable universe

Fundamental principlesFriedmann-Lemaître-Robertson-Walker metric full sky

Maximally symmetric space-timeequivalent to

where

Coordinates : full sky

Scale factor a(t):

Redshift & Expansion :

Scale factor, expansion, Hubble’s lawHubble’s flow : full sky

2 observers at comoving coordinates x1 & x2

Physical distance :

Separation velocity :

Proper velocities

Galaxy moving relative to space fabric x not constant

Velocity :

Scale factor, expansion, Hubble’s law scatter in Hubble’s law

for nearby galaxies

Einstein equations : full skygeometry energy content

Friedmann equations : dynamics of the Universe

Dynamics : Einstein, Friedmann, etc.Stress-energy tensor:

Expansion rate

Variation of H

Critical density : put full skyk = 0 today (cf. measurements!)

Density parameters :

Equation of state :

for each fluid i : pi = wiρi

Dynamics and cosmological parametersand today:

- Photons : p = ρ/3 wr=1/3
- Matter : ρ = mn, p = nkTρ wm = 0

Friedmann equations full sky

expansion

variation

acceleration

Matter-Energy conservation :

Dynamics of the Universeso clearly

(Rem: only 2 independent equations)

Evolution of a given fluid : full sky

Conservation equation gives

Summary :

* assume wi constant,

* integrate

Rem : C.C. wΛ= -1

Matter-radiation equality full sky

Expansion history wrt. dominant fluid

Universe Expansion History(from WMAP)

for zzeq : Universe dominated by radiation

Acceleration wrt. fluid equation of state of dominant fluid full sky

Deceleration

Acceleration

Universe Expansion HistoryMatter and radiation OK

Observed accelerationrequires exotic fluid withnegative pressure!

Back to the CMB… full sky

time, age

density, z, T

radiation & matter

in thermal equilibrium

radiation & matter

live separate lives

CMB : Primordial Photons’ Last Scattering full sky

380 000 years

time, age

(Planck)

density, z, T

radiation & matter

in equilibrium

via tight coupling

radiation & matter

are decoupled,

no interaction

CMB

z =1100

Download Presentation

Connecting to Server..