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    Problem interpreting Mpc/h in maps of DM

    Problem interpreting Mpc/h in "maps" of DM In charts of ρ distribution, such as the z = 0 image (taken from ), the distance scale is usually expressed in...
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    Characteristic energy units of primordial fluctuations if gaussian

    Characteristic energy "units" of primordial fluctuations if gaussian Correct me if wrong, but I think a purely gaussian distribution of the primordial fluctuations could be characterized by a certain unit of energy (which I'll express as mass). If so, then the observed fluctuations are...
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    Are thermalized neutrinos stable at temperatures their rest energy?

    At the last scattering surface (LSS), the energy density of neutrinos is argued to be ~0.68 of the energy density of blackbody photons, based on a thermodynamic equilibrium argument. This is also required to obtain the correct total energy density for stable expansion. At that time, the average...
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    Any papers out that show the observed z vs. t?

    I know the constant ΛCDM model predicts the expansion factor a (= 1/[1+z] providing we impose the condition a = 1 now) to be of the form (sinh bt)2/3 for recent times. Are there any papers that determine either a(t) or z(t) from the supernova data, showing error bars? I think that the present...
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    What is the background density of dark matter?

    Far from any superclusters, is there a background of DM which hasn't yet clumped (at least to any great extent)? What is its density compared to the average DM density (which I think averages about 1 GeV/m3 in the present)?
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    How confident are we of the neutrino CMB energy density?

    From an entropy argument it is concluded that the CMB neutrino temperature is (4/11)1/3 of the CMB photon temperature. This assumes massless neutrinos. Although neutrino contribution to the present energy density is therefore very small, it was significant must earlier, such as at the time of...
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    Can the Li7 problem be resolved by increasing the dark matter ratio?

    Currently the WMAP results give a baryon:photon ratio of ~6.2x10-10, and a dark:baryonic mass ratio of ~5. When added to the energy density of photons + neutrinos (+dark energy at later times), the total density is then critical for a flat Universe. The BB nucleosynthesis analysis of the...
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    Critical density in Early Times

    What was the total mass energy density at the time of recombination? Has it has it been measured by WMAP? (Edit: I think it's 4.28x10-18kg/m3 from the # of photons/volume in a 2979K blackbody, x baryon:photon ratio x proton mass x (1+ dark:baryon ratio) divided by the 0.755 matter fraction at...
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    Standard Candle Dimming Due to Extra Expansion

    I'm having trouble deriving the amount of dimming expected of standard candles (eg. type 1a supernovae) as a result of dark energy. Without the presence of dark energy, the standard GR solution (matter-only, at critical density) is that the absolute bolometric brightness of a standard candle...
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    Would a graviton follow the geodesic?

    A graviton, if massless, is generally expected to travel at c. If so, we would not expect it to follow the geodesic, which is the path a hypothetical particle with infinite speed. Therefore I would think for example that a massless graviton that was gravitationally lensed around a galaxy would...
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    Why is the dark matter: baryonic matter ratio about 5:1?

    All the LCDM models with variations (see ) have similar ratios of dark matter: baryonic matter density of very close to 5:1. Is this ratio determined from WMAP data such as angular size of a peak, or is it a not very tightly...
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    Does any model predict the mass (or total energy) of the observable Universe?

    During the (recently departed) matter-dominated era, the total mass of the Universe, including dark matter, is believed to have been fairly constant at around 1055 kg. This was the case in a time period from at least the CMB last scattering surface to nearly the present. Mass content is...
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    Does recent expansion change the predicted CMB temperature?

    During the interval from t = 380,000 yr (CMB last surface) to the present, if the Universe were exclusively matter at critical density, the scale factor [1+z] would be proportional to t to the 2/3 power. Note that [13.7 Gyr/380,000 yr] raised to the power 2/3 corresponds to [1+z] = 1090. This of...