Dwarf galaxies cosmology
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Dwarf galaxies & Cosmology. Jorge Peñarrubia & Matt Walker . Let’s start from the beginning …. The Universe is expanding!. Hubble 1929. Cosmology: The Equations. space-time vs mass/energy mass/energy = density/pressure. IF the Universe is isotropic and homogeneous.

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Dwarf galaxies & Cosmology

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Dwarf galaxies cosmology

Dwarf galaxies & Cosmology

Jorge Peñarrubia & Matt Walker

Let’s start from the beginning …


Dwarf galaxies cosmology

The Universe is expanding!

Hubble 1929


Dwarf galaxies cosmology

Cosmology: The Equations

space-time vs mass/energy

mass/energy = density/pressure

IF the Universe is isotropicand homogeneous

Friedman-Lemaitre-

Robertson-Walker (FLRW)

metric

Combining the above formulae …

Friedman eqs : scale factor vs time

a(t)

equation of continuity

Hubble parameter


Dwarf galaxies cosmology

Cosmology: The Equations

Equation of state of the Universe

w=0 Matter

w=1/3 Relativistic particles

Matter

Relativistic particles

Accelerating Universe


Dwarf galaxies cosmology

Cosmology: The Issues

The Homogeneity Problem “The Universe becomes less homogeneous with time due to gravity. How can we explain a Universe so smooth in the past?”

The curvature Problem

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 ?”


Dwarf galaxies cosmology

Solution: Inflation

Curvature

Horizon

aH=exp[Ht] H  H as t 0

Curvature k is not arbitrarily low ab initio

{1 –exp[-H (ti-t) ]} H-1

Horizon is not arbitrarily small at t≈0


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