Dark Universe IIDark Energy and the Shape of the UniverseThe shape of the UniverseThe fate of the UniverseOld view: Density of the Universe determines its destinyCosmological curvatureiClicker QuestioniClicker QuestioniClicker QuestioniClicker QuestioniClicker QuestioniClicker QuestionNew view: Density of the UniverseToday’s Cosmology“Geometry is not Destiny” – R. KolbDark Energy HistoryExpansion History of the UniverseHistory and fate of the UniverseRecall the Uncertainty PrincipleUncertainty PrincipleQuantum fluctuations?Does Vacuum Energy = Dark Energy?Properties of Dark EnergyConcordance ModelQuintessence ModelGravity and pressureiClicker QuestionMultiversesiClicker QuestionA Humbling ThoughtResourcesResourcesDark Universe IIDark Universe IIProf. Lynn CominskyProf. Lynn CominskyDept. of Physics and Astronomy Dept. of Physics and Astronomy Sonoma State UniversitySonoma State UniversityModifications by H. GellerModifications by H. GellerNovember 2007November 200711/27/2007 Prof. Lynn Cominsky 211/27/2007 Prof. Lynn Cominsky 3Dark Energy and the Shape of the UniverseDark Energy and the Shape of the UniverseIs the universe "open" or "closed" ?Is the universe "open" or "closed" ?How does dark energy change our view How does dark energy change our view of the history and future of the of the history and future of the universe?universe?11/27/2007 Prof. Lynn Cominsky 4The shape of the UniverseThe shape of the UniverseThe shape of the Universe is determined by a The shape of the Universe is determined by a struggle between the momentum of expansion struggle between the momentum of expansion and the pull of gravity. and the pull of gravity. The rate of expansion is determined by the The rate of expansion is determined by the Hubble Constant, Hubble Constant, HHooThe strength of gravity depends on the density The strength of gravity depends on the density and pressure of the matter in the Universe. and pressure of the matter in the Universe. GGis proportional to is proportional to ρρ+ 3P+ 3Pρρis the density and is the density and PPis the pressureis the pressureFor normal matter, For normal matter, PPis negligible, so the fate is negligible, so the fate of a universe filled with normal matter is of a universe filled with normal matter is governed by the density governed by the density ρρ11/27/2007 Prof. Lynn Cominsky 5The fate of the UniverseThe fate of the UniverseAs the universe expands, the matter spreads As the universe expands, the matter spreads out, with its density decreasing in inverse out, with its density decreasing in inverse proportion to the volume. (V = 4proportion to the volume. (V = 4ππrr33/3 for a /3 for a sphere)sphere)The strength of the curvature effect decreases The strength of the curvature effect decreases less rapidly, as the inverse of the surface area. less rapidly, as the inverse of the surface area. (A = 4(A = 4ππrr22for a sphere)for a sphere)So, in the (preSo, in the (pre--1998) standard picture of 1998) standard picture of cosmology, geometry (curvature) ultimately cosmology, geometry (curvature) ultimately gains control of the expansion of the universe. gains control of the expansion of the universe.11/27/2007 Prof. Lynn Cominsky 6Ωtotal= ΩMwhereΩM = matter density (including regular and dark matter)Ωtot= density/critical densityIf Ωtot= 1,Universe is flat, expansion coasts to a halt as Universe is critically balanced. If Ωtot> 1, Universe is closed, collapses on itself. If Ωtot< 1, Universe is open, expands forever.Old view: Old view: Density of the Universe Density of the Universe determines its destinydetermines its destiny11/27/2007 Prof. Lynn Cominsky 7Cosmological curvatureCosmological curvatureΩΩ= density of the universe / critical density= density of the universe / critical densityΩ< 1 hyperbolic geometryΩ = 1 flat or Euclidean Ω > 1 spherical geometry11/27/2007 Prof. Lynn Cominsky 8iClickeriClickerQuestionQuestionIn hyperbolic (open) geometry sum of In hyperbolic (open) geometry sum of triangles istriangles isAAequal to 180 degreesequal to 180 degreesBBless than 180 degreesless than 180 degreesCCgreater than 180 degreesgreater than 180 degrees11/27/2007 Prof. Lynn Cominsky 9iClickeriClickerQuestionQuestionIn spherical (closed) geometry sum of In spherical (closed) geometry sum of triangles istriangles isAAequal to 180 degreesequal to 180 degreesBBless than 180 degreesless than 180 degreesCCgreater than 180 degreesgreater than 180 degrees11/27/2007 Prof. Lynn Cominsky 10iClickeriClickerQuestionQuestionIn hyperbolic (open) geometry beams of In hyperbolic (open) geometry beams of light that start out parallellight that start out parallelAAalways remain parallelalways remain parallelBBactually will divergeactually will divergeCCactually will convergeactually will converge11/27/2007 Prof. Lynn Cominsky 11iClickeriClickerQuestionQuestion If Ωtot= 1A Universe is flat, expansion coasts to a halt as Universe is critically balanced. B Universe is closed, collapses on itself.C Universe is open, expands forever.11/27/2007 Prof. Lynn Cominsky 12iClickeriClickerQuestionQuestion If Ωtot< 1A Universe is flat, expansion coasts to a halt as Universe is critically balanced. B Universe is closed, collapses on itself.C Universe is open, expands forever.11/27/2007 Prof. Lynn Cominsky 13iClickeriClickerQuestionQuestion If Ωtot> 1A Universe is flat, expansion coasts to a halt as Universe is critically balanced. B Universe is closed, collapses on itself.C Universe is open, expands forever.11/27/2007 Prof. Lynn Cominsky 14After inflation ends,Ωtotal= ΩM + ΩΛ= 1.0whereΩtotal= density/critical density ΩM = matter density (including regular and dark matter) = 0.27So therefore…..ΩΛ= cosmological constant or dark energy density = 0.73 New view: Density of the UniverseNew view: Density of the UniversePerlmutter et al.40 supernovaeSN dataU R here11/27/2007 Prof. Lynn Cominsky 15Today’s CosmologyToday’s CosmologyΩΩΤΟΤ ΤΟΤ = 1.0= 1.0from CMB measurements (WMAP). from CMB measurements (WMAP). We live in a flat Universe.We live in a flat Universe.ΩΩΜ Μ <0.3<0.3from extensive observations at from extensive observations at various wavelengths. Includes dark matter as various wavelengths. Includes dark matter as well as normal matter and