Cosmology: Cosmology: Lecture course University Groningen Feb.-Apr. 2010.
Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.
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Transcript of Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.
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Dwarf galaxies & Cosmology
Let’s start from the beginning …
Jorge Peñarrubia & Matt Walker
![Page 2: Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.](https://reader035.fdocuments.in/reader035/viewer/2022062301/56649d2f5503460f94a06a2b/html5/thumbnails/2.jpg)
The Universe is expanding!
Hubble 1929
![Page 3: Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.](https://reader035.fdocuments.in/reader035/viewer/2022062301/56649d2f5503460f94a06a2b/html5/thumbnails/3.jpg)
Cosmology: The Equations
space-time vs mass/energy
mass/energy = density/pressure
IF the Universe is isotropic and homogeneous Friedman-Lemaitre-Robertson-Walker (FLRW)metric
Combining the above formulae …
Friedman eqs : scale factor vs time
a(t)
equation of continuity
Hubble parameter
![Page 4: Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.](https://reader035.fdocuments.in/reader035/viewer/2022062301/56649d2f5503460f94a06a2b/html5/thumbnails/4.jpg)
Cosmology: The Equations
Equation of state of the Universew=0 Matterw=1/3 Relativistic particles
Matter
Relativistic particles
Accelerating Universe
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Cosmology: The Issues
1. The Homogeneity Problem “The Universe becomes less homogeneous with time due to gravity. How can we explain a Universe so smooth in the past?”
2. The curvature Problem
3. The Horizon Problem
observations: Ω0 ≈1
theory:
“The curvature of the Universe was very small at t≈0 “
Co-moving Horizon (aH)-1 tends to zero as t≈0
“How can the CMB be so homogeneous if different regions were not casually-connected at t≈0 ?”
![Page 6: Dwarf galaxies & Cosmology Let’s start from the beginning … Jorge Peñarrubia & Matt Walker.](https://reader035.fdocuments.in/reader035/viewer/2022062301/56649d2f5503460f94a06a2b/html5/thumbnails/6.jpg)
Solution: Inflation
1. Curvature
2. Horizon
aH=exp[Ht] H H as t 0Curvature k is not arbitrarily low ab initio
{1 –exp[-H (ti -t) ]} H-1
Horizon is not arbitrarily small at t≈0