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Types of Dark Matter and the Evolution of the Universe

Explore the structure, evolution, and types of WIMPS in the universe, including bottom-up (CDM) and top-down (HDM) theories. Understand the concepts of "cold" and "hot" dark matter and their impact on the formation of galaxies. Discover the role of the Cosmic Microwave Background (CMB) and supernovae in determining the composition and expansion of the universe.

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Types of Dark Matter and the Evolution of the Universe

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  1. More buzz words, etc. • Structure evolution and types of WIMPS • Bottom-up <=> Cold Dark Matter(CDM) • Top-Down <=> Hot Dark Matter (HDM) • “Cold” = “slow” = less then 1/10 speed of light • “Hot” = “fast” = 0.99 or closer to speed of light • Galaxies seen far away => formed early = bottom up = CDM

  2. Key points to derivation ofwe live in flat universe From CBM: We assume we know how to calculate the size of the brick wall fluctuations! [Remember we assume ADIABATIC fluctuations] Apparent size depends ENTIRELY on the curvature of the of the universe => we think we’re flat “for sure” But only if adiabatic fluctuations apply!

  3. Is there a way out? Yes! =“Isocurvature” fluctuations • Dissociate the matter from the light • “Brick wall” can be as smooth as you please • Apparent size of the brick wall fluctuations • Ambiguous => • Assume a size that agrees with any geometry • ( k = -1, 0 , 0r 1

  4. Summary: CMB associated with Big Bang BB plus GR says Universe was hot and is expanding CMB measurements with model fitting: Most likely universe is flat

  5. Summary cont.: If universe is flat, there is lots (90%-95%) of something that is not ordinary (baryonic) matter. But clusters say only 30% of W can come from all forms of matter. Therefore CMB + Clusters says need Dark Energy to make up the difference Agrees with SNe Ia

  6. CMB SNe Ia clusters

  7. Summary Cont. So Wm = 0.3, WL= 0.7, k = 0 (flat) will expand forever in an accelerating manner • Problem is “crazy” universe: • Dark Energy, non-baryonic matter, invisible baryonic matter. Ways out: • We’ve just screwed up big time • Isocurvature can remove dark energy (from k = 0 and matter limits) from CMB measurements BUT still have SN Ia! Time will tell

  8. Brick Building or Pack of Cards? Clusters say Wm 0.3 “Final” Answer: Wt = W_L +Wm = 1; k = 0; Wb = 0.05, WCDM = 0.25, WL = 0.7 Supernovae says dark energy CDM CMB “1st peak,” universe flat = Wtotal = 1, k = 0 Galaxies formed early Non-ordinary [but real] matter (non-baryonic), lots Big Bang Galaxies and Clusters exist GR + CMB total +expanding universe General Smoothness of CMB

  9. Onwardho! • OK, where do supernovae fit in and how? • First the concept: the standard candle • If know how bright something is intrinsically, then if you can measure it’s apparent brightness, you can calculate the Distance (D) • Apparent brightness = intrinsic brightness/4pD2 • For Euclidian spaceD is “normal”

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