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  • Introduction Acoustic Oscillations Baryonmeter Doppler Effect Driving Effect Damping Projection ISW Effect Power Spectrum Sensitivity Secondary Anisotropy Summary

    Original URL path: http://background.uchicago.edu/~whu/physics/tour.inc (2015-06-26)
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  • Tour
    Figure From temperature differences to anisotropies We believe that large scale structure in the universe grew out of small perturbations in the early universe through gravitational instability This implies that the photon baryon fluid moves in a gravitational potential well before last scattering For the technically minded this assumes a Newtonian representation of perturbations or gauge The response of the fluid to the gravitational potential fluctuations allow us to measure the properties of the fluid in an expanding universe known to be filled with dark matter which allows us to extract basic cosmological parameters as well as those of the seed perturbations which can be used to pin down the nature of large scale structure formation in the universe To extract this sort of information we must analyze a map of the CMB sky such as that displayed at the top of this page from the original COBE satellite detection in 1992 Basically we want to take the power spectrum of this primordial noise Since the fluctuations are on the sky this amounts to taking an angular decomposition of the fluctuations in multipole space l proportional to the inverse angle rather than Fourier space k where the underlying potential fluctuations

    Original URL path: http://background.uchicago.edu/~whu/physics/tourpage.html (2015-06-26)
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  • TRANSFER
    upcoming Sloan Digital Sky Survey should detect N nearly degenerate massive neutrino species with mass m nu 0 65 Omega m h 2 0 1 N 0 8 eV at better than 2 sigma once cosmic microwave background experiments which are themselves insensitive to m nu measure two other cosmological parameters There is significant overlap between this region and that implied by the LSND experiment and even m nu 0

    Original URL path: http://background.uchicago.edu/~whu/neutrino/neutrinopage.html (2015-06-26)
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  • CMB Experiments
    familiar force of gravity is no more than the curvature of space time To see this fact consider the surface of the Earth Two people travelling due north from the Equator on different lines of longitude will nonetheless meet at the North Pole Ignorant of the curvature of the earth they might attribute this fact to a strange attractive force The same thing happens to CMB photons on their way to the observer if the Universe is spatially curved The intervening matter and energy acts as a giant de magnifying glass that bends the photon trajectories The BOOMERanG result supports a flat Universe which means that the total mass and energy density of the Universe is equal to the so called critical density A perfectly flat Universe will remain at the critical density and keep on expanding forever because there is not enough matter to make it recollapse in a big crunch So this argument would make it seem like we already know the fate of the Universe from the results Unfortunately we don t know that it is perfectly flat We only know that across the 10 20 billion light years that the CMB photons have travelled there is no detectable curvature In the earth analogy it may be that on a clear day we can see for several miles Over those several miles the earth appears flat But the earth is not flat Our observation simply tells us that the radius of the earth is much larger than the distance across which we looked Likewise the BOOMERanG results say that the Universe is nearly flat across the observable Universe Over time more and more of the Universe becomes visible as light from more distant locations reach us It may be that we will eventually discover the Universe is closed and will recollapse We just know that it won t do so in the next few tens of billions of years 5 I ve heard that the position of the first peak actually implies the Universe is not flat but closed Is this true This comes back to the question of nearly flat The first peak as observed by BOOMERanG is at about a 10 larger angular scale than we expected from previous measurements and predictions of our previous best guess cosmology This is a small shift and there are uncertainties associated with the measurement so there is no cause for alarm yet There are several effects that can shift the peak in that direction by 10 or so It is true that one of them is to keep the dark matter density low but make the Universe closed by the cosmological constant Another is to make the dark matter density in physical units higher This can be achieved by either raising its density compared with the critical density higher than the standard 1 3 value or raising the Hubble constant from 65 to 75 km s Mpc Yet another solution is to slow the acceleration of the Universe

    Original URL path: http://background.uchicago.edu/~whu/faq.html (2015-06-26)
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  • CMB Experiments
    5uK noise to be conservative with respect to foregrounds and systematics Polarization Current Ongoing Projected MAP Projected Planck Notes current status shows order of magnitude limits and a rough estimate of the angular coverage and sensitivity of the planned Polar and Polatron experiments MAP polarization assumes 3 polarized channels Planck temperature 3LFI channels 4HFI channels and polarization 3HFI channels These are raw sensitivity limits and may not be achieved in

    Original URL path: http://background.uchicago.edu/~whu/cmbexpageold.html (2015-06-26)
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  • Chuangtzu
    in it With his outrageous opinions reckless words extravagant formulations he was sometimes too free but was not partisan he did not show things from one particular point of view He thought that the empire was sinking in the mud and could not be talked with in too solemn language Although is writings are extraordinary there is no harm in their oddities Although his formulations are irregular their enigmas deserve

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