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## Cosmic Inflation Phy 262 2013 Andreas Albrecht

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**Cosmic Inflation**Phy 262 2013 Andreas Albrecht A. Albrecht @ Stanford Jan 7 2013**Cosmic Inflation:**• Great phenomenology, but • Original goal of explaining why the cosmos is *likely* to take the form we observe has proven very difficult to realize. A. Albrecht @ Stanford Jan 7 2013**Cosmic Inflation:**• Great phenomenology, but • Original goal of explaining why the cosmos is *likely* to take the form we observe has proven very difficult to realize. This Talk A. Albrecht @ Stanford Jan 7 2013**Cosmic Inflation:**• Great phenomenology, but • Original goal of explaining why the cosmos is *likely* to take the form we observe has proven very difficult to realize. • OR: Just be happy we have equations to solve? A. Albrecht @ Stanford Jan 7 2013**OUTLINE**Big Bang & inflation basics Eternal inflation de Sitter Equilibrium cosmology Cosmic curvature from de Sitter Equilibrium cosmology A. Albrecht @ Stanford Jan 7 2013**OUTLINE**Big Bang & inflation basics Eternal inflation de Sitter Equilibrium cosmology Cosmic curvature from de Sitter Equilibrium cosmology A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Hubble parameter (“constant”, because today it takes ~10Billion years to change appreciable) A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Hubble parameter (“constant”, because today it takes ~10Billion years to change appreciable) “Scale factor” A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Curvature “Scale factor” A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Curvature Relativistic Matter “Scale factor” A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Curvature Non-relativistic Matter Relativistic Matter “Scale factor” A. Albrecht @ Stanford Jan 7 2013**Friedmann Eqn.**Dark Energy Curvature Non-relativistic Matter Relativistic Matter “Scale factor” A. Albrecht @ Stanford Jan 7 2013**Evolution of Cosmic Matter**A. Albrecht @ Stanford Jan 7 2013**Evolution of Cosmic Matter**A. Albrecht @ Stanford Jan 7 2013**Evolution of Cosmic Matter**A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**! A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**! A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**! A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**A. Albrecht @ Stanford Jan 7 2013**The curvature feature/“problem”**! A. Albrecht @ Stanford Jan 7 2013**i**W a 1 In the SBB, flatness is an “unstable fixed point”: Dominates with time At or The “GUT scale” Require today to 55 decimal places to get I.0 What is Cosmic Inflation?**i**W a 1 In the SBB, flatness is an “unstable fixed point”: SBB = “Standard Big Bang” cosmology, or “cosmology without inflation”. Dominates with time At or The “GUT scale” Require today to 55 decimal places to get I.0 What is Cosmic Inflation?**i**Gravitational instability: The Jeans Length Average energy density Sound speed • Overdense regions of size • collapse under their own weight. • If the size is they just oscillate I.0 What is Cosmic Inflation?**i**SBB Homogeneity: On very large scales the Universe is highly homogeneous, despite the fact that gravity will clump matter on scales greater than RJeans At the GUT epoch the observed Universe consisted of 1079RJeanssized regions. The Universe was very smooth to start with. NB: Flatness & Homogeneity SBB Universe starts in highly unstable state. I.0 What is Cosmic Inflation?**i**SBB Monopoles • A GUT phase transition (or any other process) that injects stable non-relativistic matter into the universe at early times (deep in radiation era, ie Ti =1016 GeV) will *ruin* cosmology: Monopole dominated Universe I.0 What is Cosmic Inflation?**The monopole “problem”**A. Albrecht @ Stanford Jan 7 2013**The monopole “problem”**! A. Albrecht @ Stanford Jan 7 2013**i**Here & Now SBB Horizon t=0 1080 causally disconnected regions at the GUT epoch Horizon: The distance light has traveled since the big bang: I.0 What is Cosmic Inflation?**The flatness, homogeneity & horizon features become**“problems” if one feels one must explain initial conditions. Basically, the SBB says the universe must start in a highly balanced (or “fine tuned”) state, like a pencil on its point. Must/can one explain this? Inflation says “yes” I.0 What is Cosmic Inflation?**Friedmann Eqn.**Dark Energy Curvature Non-relativistic Matter Relativistic Matter A. Albrecht @ Stanford Jan 7 2013**Now add cosmic inflation**Friedmann Eqn. Dark Energy Inflaton Curvature Non-relativistic Matter Relativistic Matter A. Albrecht @ Stanford Jan 7 2013**Now add cosmic inflation**Friedmann Eqn. Dark Energy Inflaton Curvature Non-relativistic Matter Relativistic Matter A. Albrecht @ Stanford Jan 7 2013**Now add cosmic inflation**Friedmann Eqn. Dark Energy Inflaton Curvature Non-relativistic Matter Relativistic Matter A. Albrecht @ Stanford Jan 7 2013**The inflaton:**~Homogeneous scalar field obeying Cosmic damping Coupling to ordinary matter All potentials have a “low roll” (overdamped) regime where A. Albrecht @ Stanford Jan 7 2013**The inflaton:**~Homogeneous scalar field obeying Cosmic damping Coupling to ordinary matter All potentials have a “low roll” (overdamped) regime where A. Albrecht @ Stanford Jan 7 2013**Add a period of Inflation:**A. Albrecht @ Stanford Jan 7 2013**With inflation, initially large curvature is OK:**A. Albrecht @ Stanford Jan 7 2013**With inflation, early production of large amounts of**non-relativistic matter (monopoles) is ok : A. Albrecht @ Stanford Jan 7 2013**With inflation, early production of large amounts of**non-relativistic matter (monopoles) is ok : A. Albrecht @ Stanford Jan 7 2013**Inflation detail:**A. Albrecht @ Stanford Jan 7 2013**Inflation detail:**A. Albrecht @ Stanford Jan 7 2013**Hubble Length**A. Albrecht @ Stanford Jan 7 2013**Hubble Length**(aka ) A. Albrecht @ Stanford Jan 7 2013