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  • CMB Introduction
    Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations Gravity Plane Waves Harmonics Extrema Angular Peaks Spatial Angular Oscillation Freeze Frame Streaming Soundscape First Peak Data Curvature Flatness Dark Energy Summary Second Peak Data Inertia Baryonmeter Power Dark Baryons Summary Higher Peaks Driving Force Power Summary Damping Tail Diffusion Ruler Consistency Summary Parameter Estimation Parameters Degeneracy Polarization What and Why Scattering Projection Power Quadrupoles B modes Gravity Waves Summary Dark Baryons Key Concepts Second peak is observed to be substantially lower than first peak Dark baryons of at least the big bang nucleosynethesis density required Although we cannot yet claim that the second peak is as precisely measured as the first we can say that assuming it exists it is definitely of lower amplitude than the first The current data indicate that the baryon density is around Omega b h 2 0 02 This value is interesting since it is also the baryon density inferred from the abundance of

    Original URL path: http://background.uchicago.edu/~whu/intermediate/baryons4.html (2015-06-26)
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  • CMB Introduction
    for CAMB Halo Mass Conversion Cluster Abundance Cosmology 321 Current Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations Gravity Plane Waves Harmonics Extrema Angular Peaks Spatial Angular Oscillation

    Original URL path: http://background.uchicago.edu/~whu/intermediate/score2.html (2015-06-26)
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  • CMB Introduction
    Oscillations Cosmic Shear Clusters Transfer Function WMAP Likelihood Reionization PPF for CAMB Halo Mass Conversion Cluster Abundance Cosmology 321 Current Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations

    Original URL path: http://background.uchicago.edu/~whu/intermediate/higher.html (2015-06-26)
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  • CMB Introduction
    Data Inertia Baryonmeter Power Dark Baryons Summary Higher Peaks Driving Force Power Summary Damping Tail Diffusion Ruler Consistency Summary Parameter Estimation Parameters Degeneracy Polarization What and Why Scattering Projection Power Quadrupoles B modes Gravity Waves Summary Radiation Driving Force Key Concepts Radiation dominates the universe early on Pressure support in the radiation causes the gravitational potential to decay The decay occurs at exactly the right time to drive the amplitude of the oscillations up The higher peaks began their oscillation in the radiation dominated universe and have an enhanced amplitude The series of higher acoustic peaks is sensitive to the energy density ratio of dark matter to radiation in the universe Because the amount of radiation is known from the measured temperature of the CMB and the thermal history under normal assumptions the higher acoustic peaks are sensitive to the dark matter density in the universe Let s see how that works What happens is that if the energy density of the radiation dominates the matter density we can no longer consider the photon baryon fluid to be oscillating in a fixed gravitational potential well In fact the potential decays away at just the right time to drive the amplitude of the oscillations up This timing is not a coincidence What happens is that if the radiation dominates the density it is also what is making the gravitational potential in the first place Mathematically the Poisson equation relates the overdensity of photons to the gravitational potential As pressure stops the radiation from further compression the density fluctuation stabilizes leaving the gravitational potential to decay with the expansion of the universe The decay happens when the fluid is in its most compressed state The fluid now sees no gravitational potential to fight against as it bounces back and the amplitude of

    Original URL path: http://background.uchicago.edu/~whu/intermediate/driving.html (2015-06-26)
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  • CMB Introduction
    Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations Gravity Plane Waves Harmonics Extrema Angular Peaks Spatial Angular Oscillation Freeze Frame Streaming Soundscape First Peak Data Curvature Flatness Dark Energy Summary Second Peak Data Inertia Baryonmeter Power Dark Baryons Summary Higher Peaks Driving Force Power Summary Damping Tail Diffusion Ruler Consistency Summary Parameter Estimation Parameters Degeneracy Polarization What and Why Scattering Projection Power Quadrupoles B modes Gravity Waves Summary Dark Matter Density Key Concepts Raising the dark matter density reduces the overall amplitude of the peaks Lowering the dark matter density eliminates the baryon loading effect so that a high third peak is an indication of dark matter With three peaks its effects are distinct from the baryons Measuring the dark matter density resolves the main ambiguity in the curvature measurement As advertised the acoustic peaks in the power spectrum are sensitive to the dark matter density in the universe Formally the matter to radiation ratio but the radiation density is fixed in the standard model As we raise the physical density of the dark matter W m h 2 the driving effect goes away at a given peak such that its amplitude decreases Although this effect changes the heights of all the peaks it is only separable from the baryonic effects with at least three peaks Note that decreasing the matter density also affects the baryon loading since the dark matter potential wells go away leaving nothing for the baryons to fall into Having a third peak that is boosted to a height comparable to or exceeding the second peak is an indication that dark matter dominated the matter density in the plasma before recombination Note that the self gravity of the photons

    Original URL path: http://background.uchicago.edu/~whu/intermediate/driving2.html (2015-06-26)
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  • CMB Introduction
    Abundance Cosmology 321 Current Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations Gravity Plane Waves Harmonics Extrema Angular Peaks Spatial Angular Oscillation Freeze Frame Streaming Soundscape First Peak

    Original URL path: http://background.uchicago.edu/~whu/intermediate/score3.html (2015-06-26)
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  • CMB Introduction
    Oscillations Cosmic Shear Clusters Transfer Function WMAP Likelihood Reionization PPF for CAMB Halo Mass Conversion Cluster Abundance Cosmology 321 Current Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations

    Original URL path: http://background.uchicago.edu/~whu/intermediate/damping.html (2015-06-26)
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  • CMB Introduction
    Halo Mass Conversion Cluster Abundance Cosmology 321 Current Topics 282 Galaxies and Universe 242 Radiative Processes 305 Research Preparation 307 GR Perturbation Theory 408 Advanced CMB 448 University of Chicago Astronomy Department KICP Thunch astro ph CO ADS InSpire Introduction Temperature Maps Earth Monopole Dipole COBE Power Precision Features Thermal History Expansion Plasma Glue Pressure Thermal Acoustic Oscillations Gravity Plane Waves Harmonics Extrema Angular Peaks Spatial Angular Oscillation Freeze Frame Streaming Soundscape First Peak Data Curvature Flatness Dark Energy Summary Second Peak Data Inertia Baryonmeter Power Dark Baryons Summary Higher Peaks Driving Force Power Summary Damping Tail Diffusion Ruler Consistency Summary Parameter Estimation Parameters Degeneracy Polarization What and Why Scattering Projection Power Quadrupoles B modes Gravity Waves Summary Diffusion Damping Key Concepts CMB photons bounce around random walk through the baryons during recombination For fluctuations with a short wavelength hot and cold photons mix The acoustic peaks are exponentially damped on scales smaller than the distance photons random walk during recombination The alert reader will have noticed that in all cases the amplitude of the acoustic peaks drops off rapidly at the highest multipoles or smallest angular scales What happens is the physical scale of these fluctuations are so small

    Original URL path: http://background.uchicago.edu/~whu/intermediate/damping1.html (2015-06-26)
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