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Dwarf galaxies & Cosmology

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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  1. Dwarf galaxies & Cosmology Jorge Peñarrubia & Matt Walker Let’s start from the beginning …

  2. The Universe is expanding! Hubble 1929

  3. 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

  4. Cosmology: The Equations Equation of state of the Universe w=0 Matter w=1/3 Relativistic particles Matter Relativistic particles Accelerating Universe

  5. 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 ?”

  6. 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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