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What will we learn from the CMB?

Description: Within the next decade, experiments measuring the anisotropies in the cosmic microwave background (CMB) will add greatly to our knowledge of the universe. There are dozens of experiments scheduled to take data over the next several years, capped by the satellite missions of NASA (MAP) and ESA (PLANCK). What will we learn from these experiments? I argue that the potential pay-off is immense: We are quite likely to determine cosmological parameters to unprecedented accuracy. This will provide key information about the theory of structure formation and even about the physics behind inflation. If the experiments succeed, can anything spoil this pay-off? I focus on three possible spoilers - foregrounds, reionization, and defect models - and argue that we have every reason to be optimistic.
Date: October 1, 1997
Creator: Dodelson, S.
Partner: UNT Libraries Government Documents Department

The CMBR spectrum

Description: Here we give an introduction to the observed spectrum of the Cosmic Microwave Background Radiation (CMBR) and discuss what can be learned about it. Particular attention will be given to how Compton scattering can distort the spectrum of the CMBR. An incomplete bibliography of relevant papers is also provided.
Date: May 1, 1997
Creator: Stebbins, A.
Partner: UNT Libraries Government Documents Department

Anisotropies in the cosmic microwave background: Theory

Description: Anisotropies in the Cosmic Microwave Background (CMB) contain a wealth of information about the past history of the universe and the present values of cosmological parameters. I online some of the theoretical advances of the last few years. In particular, I emphasize that for a wide class of cosmological models, theorists can accurately calculate the spectrum to better than a percent. The spectrum of anisotropies today is directly related to the pattern of inhomogeneities present at the time of recombination. This recognition leads to a powerful argument that will enable us to distinguish inflationary models from other models of structure formation. If the inflationary models turn out to be correct, the free parameters in these models will be determined to unprecedented accuracy by the upcoming satellite missions.
Date: February 1, 1998
Creator: Dodelson, S.
Partner: UNT Libraries Government Documents Department

New inflation vs. chaotic inflation, higher degree potentials and the reconstruction program in light of WMAP3

Description: The cosmic microwave background power spectra are studied for different families of single field new and chaotic inflation models in the effective field theory approach to inflation. We implement a systematic expansion in 1/N(e), where N(e)~;;50 is the number of e-folds before the end of inflation. We study the dependence of the observables (n(s), r and dn(s)/dlnk) on the degree of the potential (2n) and confront them to the WMAP3 and large scale structure data: This shows in general that fourth degree potentials (n=2) provide the best fit to the data; the window of consistency with the WMAP3 and LSS data narrows for growing n. New inflation yields a good fit to the r and n(s) data in a wide range of field and parameter space. Small field inflation yields r<0.16 while large field inflation yields r>0.16 (for N(e)=50). All members of the new inflation family predict a small but negative running -4(n+1) x 10-4<=dn(s)/dlnk<=-2 x 10-4. (The values of r, n(s), dn(s)/dlnk for arbitrary N(e) follow by a simple rescaling from the N(e)=50 values.) A reconstruction program is carried out suggesting quite generally that for n(s) consistent with the WMAP3 and LSS data and r<0.1 the symmetry breaking scale for new inflation is |phi0|~;;10MPl while the field scale at Hubble crossing is lbar phi(c) rbar~;;M(Pl). The family of chaotic models features r>=0.16 (for N(e)=50) and only a restricted subset of chaotic models are consistent with the combined WMAP3 bounds on r, n(s), dn(s)/dlnk with a narrow window in field amplitude around |phi(c)|~;;15M(Pl). We conclude that a measurement of r<0.16 (for N(e)=50) distinctly rules out a large class of chaotic scenarios and favors small field new inflationary models. As a general consequence, new inflation emerges more favored than chaotic inflation.
Date: February 12, 2007
Creator: Ho, Chiu Man; Boyanovsky, D.; de Vega, H.J.; Ho, C.M. & Sanchez, N.G.
Partner: UNT Libraries Government Documents Department

Using the cosmic microwave background to discriminate among inflation models

Description: The upcoming satellite missions MAP and Planck will measure the spectrum of fluctuations in the Cosmic Microwave Background with unprecedented accuracy. I discuss the prospect of using these observations to distinguish among proposed models of inflationary cosmology.
Date: December 23, 1997
Creator: Kinney, W.H.
Partner: UNT Libraries Government Documents Department

Long-Wavelength Measurements of the Cosmic Microwave BackgroundRadiation Spectrum

Description: We have measured the temperature of the cosmic microwave background radiation at wavelengths of 0.33, 3.0, 8.2 and 21.3 cm. These measurements represent a continuation of the work reported by Smoot et al. (1985). The new results have a weighted average of 2.70 {+-} 0.05 K and are consistent with past measurements. They limit the possible distortion of the cosmic microwave background radiation spectrum to less than 6%. The results of all measurements to date are consistent with a Planckian spectrum with temperature 2.74 {+-} 0.02 K spanning a wavelength range of 0.1 to 21 cm.
Date: February 1, 1987
Creator: Smoot, G.F.; Bensadoun, M.; Bersanelli, M.; pDe Amici, G.; Kogut,A.; Levine, S. et al.
Partner: UNT Libraries Government Documents Department

Performance characteristics of a cosmology package on leading HPCarchitectures

Description: The Cosmic Microwave Background (CMB) is a snapshot of the Universe some 400,000 years after the Big Bang. The pattern of anisotropies in the CMB carries a wealth of information about the fundamental parameters of cosmology. Extracting this information is an extremely computationally expensive endeavor, requiring massively parallel computers and software packages capable of exploiting them. One such package is the Microwave Anisotropy Dataset Computational Analysis Package (MADCAP) which has been used to analyze data from a number of CMB experiments. In this work, we compare MADCAP performance on the vector-based Earth Simulator (ES) and Cray X1 architectures and two leading superscalar systems, the IBM Power3 and Power4. Our results highlight the complex interplay between the problem size, architectural paradigm, interconnect, and vendor-supplied numerical libraries, while isolating the I/O file system as the key bottleneck across all the platforms.
Date: January 1, 2004
Creator: Carter, Jonathan; Borrill, Julian & Oliker, Leonid
Partner: UNT Libraries Government Documents Department

On the computation of CMBR anisotropies from simulations of topological defects

Description: Techniques for computing the CMBR anisotropy from simulations of topological defects are discussed with an eye to getting as much information from a simulation as possible. Here we consider the practical details of which sums and multiplications to do and how many terms there are.
Date: May 1, 1997
Creator: Stebbins, A. & Dodelson, S.
Partner: UNT Libraries Government Documents Department

Primordial non-Gaussianity and Dark Energy constraints from Cluster Surveys

Description: Galaxy cluster surveys will be a powerful probe of dark energy. At the same time, cluster abundances is sensitive to any non-Gaussianity of the primordial density field. It is therefore possible that non-Gaussian initial conditions might be misinterpreted as a sign of dark energy or at least degrade the expected constraints on dark energy parameters. To address this issue, we perform a likelihood analysis of an ideal cluster survey similar in size and depth to the upcoming South Pole Telescope/Dark Energy Survey (SPT-DES).We analyze a model in which the strength of the non-Gaussianity is parameterized by the constant f{sub NL}; this model has been used extensively to derive Cosmic Microwave Background (CMB) anisotropy constraints on non-Gaussianity, allowing us to make contact with those works. We find that the constraining power of the cluster survey on dark energy observables is not significantly diminished by non-Gaussianity provided that cluster redshift information is included in the analysis. We also find that even an ideal cluster survey is unlikely to improve significantly current and future CMB constraints on non-Gaussianity. However, when all systematics are under control, it could constitute a valuable cross check to CMB observations.
Date: September 1, 2006
Creator: Sefusatti, Emiliano; Vale, Chris; /Fermilab; Kadota, Kenji; /Fermilab /Minnesota U., Theor. Phys. Inst.; Frieman, Joshua et al.
Partner: UNT Libraries Government Documents Department

Measuring velocites using the CMB & LSS

Description: Here is discussed various ways by which the cosmic microwave background (CMB) radiation can be use to measure the velocities of matter in the universe. We include some new statistical techniques for using the kinetic Sunyaev-Zel'dovich (kSZ) effect and integrated Sachs-Wolfe (ISW) effect to determine velocities by correlating wide area CMB maps with overlapping large-scale structure (LSS) surveys.
Date: July 1, 2006
Creator: Stebbins, Albert & /Fermilab /Paris, Inst. Astrophys.
Partner: UNT Libraries Government Documents Department

The Spectrumof the Cosmic Background Radiation: Early and RecentMeasurements from the White Mountain Research Station

Description: The White Mountain Research Station has provided a support facility at a high, dry, radio-quiet site for measurements that have established the blackbody character of the cosmic microwave background radiation. This finding has confirmed the interpretation of the radiation as a relic of the primeval fireball and helped to establish the hot Big Bang theory as the standard cosmological model.
Date: September 1, 1985
Creator: Smoot, G. F.
Partner: UNT Libraries Government Documents Department

An Analysis of Recent Measurements of the Temperature of theCosmic Microwave Background Radiation

Description: This paper presents an analysis of the results of recent temperature measurements of the cosmic microwave background radiation (CMBR). The observations for wavelengths longer than 0.1 cm are well fit by a blackbody spectrum at 2.74 {+-} 0.02 K; however, including the new data of Matsumoto et al. (1987) the result is no longer consistent with a Planckian spectrum. The data are described by a Thomson-distortion parameter u = 0.021 {+-} 0.002 and temperature 2.823 {+-} 0.010 K at the 68% confidence level. Fitting the low-frequency data to a Bose-Einstein spectral distortion yields a 95% confidence level upper limit of 1.4 x 10{sup -2} on the chemical potential {mu}{sub 0}. These limits on spectral distortions place restrictions on a number of potentially interesting sources of energy release to the CMBR, including the hot intergalactic medium proposed as the source of the X-ray background.
Date: July 1, 1987
Creator: Smoot, G.; Levin, S.M.; Witebsky, C.; De Amici, G. & Rephaeli, Y.
Partner: UNT Libraries Government Documents Department

The Coyote Universe II: Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

Description: The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the 'Coyote Universe' suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.
Date: January 1, 2008
Creator: Heitmann, Katrin; Habib, Salman; Higdon, David; Williams, Brian J; White, Martin & Wagner, Christian
Partner: UNT Libraries Government Documents Department

Is Ursa Major II the Progenitor of the Orphan Stream?

Description: Prominent in the ''Field of Streams''--the Sloan Digital Sky Survey map of substructure in the Galactic halo--is an ''Orphan Stream'' without obvious progenitor. In this numerical study, we show a possible connection between the newly found dwarf satellite Ursa Major II (UMa II) and the Orphan Stream. We provide numerical simulations of the disruption of UMa II that match the observational data on the position, distance and morphology of the Orphan Stream. We predict the radial velocity of UMa II as -100kms{sup -1}, as well as the existence of strong velocity gradients along the Orphan Stream. The velocity dispersion of UMa II is expected to be high, though this can be caused both by a high dark matter content or by the presence of unbound stars in a disrupted remnant. However, the existence of a gradient in the mean radial velocity across UMa II provides a clear-cut distinction between these possibilities. The simulations support the idea that some of the anomalous, young halo globular clusters like Palomar 1 or Arp 2 or Ruprecht 106 may be physically associated with the Orphan Stream.
Date: November 1, 2006
Creator: Fellhauer, M.; Evans, N. W.; Belokurov, V.; Zucker, D. B.; Yanny, B.; Wilkinson, M. I. et al.
Partner: UNT Libraries Government Documents Department

Low-Frequency Measurements of the CMB Spectrum

Description: As part of an extended program to characterize the spectrum of the cosmic microwave background (CMB) at low frequencies, we have performed multiple measurements from a high-altitude site in California. On average, these measurements suggest a CMB temperature slightly lower than measurements at higher frequencies. Atmospheric conditions and the encroachment of civilization are now significant limitations from our present observing site. In November 1989, we will make new measurements from the South Pole Amundsen-Scott Station at frequencies 0.82, 1.5, 2.5, 3.8, 7.5, and 90 GHz. We discuss recent measurements and indicate improvements possible from a polar observing site.
Date: October 1, 1989
Creator: Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Limon,M.; Smoot, George F. et al.
Partner: UNT Libraries Government Documents Department

Review of Cosmic Background Radiation Spectrum Measurements:Limits on Distortions, Energy Release, and Cosmological Processes

Description: This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 {+-} 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.
Date: January 1, 1986
Creator: Smoot, G.F.
Partner: UNT Libraries Government Documents Department

Relic neutrino detector

Description: Probably the most promising way of detecting cosmic neutrinos is measuring the mechanical force exerted by clastic scattering of cosmic neutrinos from macroscopic targets. The expected acceleration is ~10<sup>-23</sup>cm/s<sup>2</sup> for Dirac neutrinos of mass ~10 eV and local density ~10<sup>7</sup>/cm<sup>3</sup>. A novel torsion balance design is presented, which addresses the sensitivity-limiting factors of existing balances, such as seismic and thermal noise, and angular readout resolution and stability.
Date: January 27, 1999
Creator: Hagmann, C.
Partner: UNT Libraries Government Documents Department

Cosmic microwave background: Past, future, and present

Description: Anisotropies in the Cosmic Microwave Background (CMB) carry an enormous amount of information about the early universe. The anisotropy spectrum depends sensitively on close to a dozen cosmological parameters, some of which have never been measured before. Experiments over the next decade will help us extract these parameters, teaching us not only about the early universe, but also about physics at unprecedented energies. One of the dangers now is that scientist are tempted to ignore the present data and rely too much on the future. This would be a shame, for hundreds of individuals have put in a great amount of time building state-of-the-art instruments, making painstaking observations at remote places on and off the globe. It seems unfair to ignore all the data that has been taken to date simply because there will be more and better data in the future. The author then makes the following claims: (1) the theory of CMB anisotropies is understood; (2) using this understanding, he is able to extract from future observations extremely accurate measurements of about ten cosmological parameters; (3) taken at face value, present data determines one of these parameters, the curvature of the universe; and (4) the present data is good enough that the measurements should be believed. The first of these claims are well-known. The last claim is more controversial, but the author presents evidence for it.
Date: April 10, 2000
Creator: Dodelson, S.
Partner: UNT Libraries Government Documents Department

Large-scale structure from quantum fluctuations in the early universe

Description: A better understanding of the formation of large-scale structure in the Universe is arguably the most pressing question in cosmology. The most compelling and promising theoretical paradigm, Inflation + Cold Dark Matter, holds that the density inhomogeneities that seeded the formation of structure in the Universe originated from quantum fluctuations arising during inflation and that the bulk of the dark matter exists as slowing moving elementary particles (cold dark matter) left over from the earliest, fiery moments. Large redshift surveys (such as the SDSS and 2dF) and high-resolution measurements of CBR anisotropy (to be made by the MAP and Planck Surveyor satellites) have the potential to decisively test Inflation + Cold Dark Matter and to open a window to the very early Universe and fundamental physics.
Date: May 25, 2000
Creator: Turner, Michael
Partner: UNT Libraries Government Documents Department

Cosmological Consequences of String Axions

Description: Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the consequences of a measurement of these fluctuations for two additional string axions. We do so independent of any cosmological assumptions except for the axions being massless during inflation. The first axion has been shown to solve the strong CP problem for most compactifications of the heterotic string while the second axion, which does not solve the strong CP problem, obeys a mass formula which is independent of the axion scale. We find that if gravitational waves interpreted as arising from inflation are observed by the PLANCK polarimetry experiment with a Hubble constant during inflation of H{sub inf} {approx}&gt; 10{sup 13} GeV the existence of the first axion is ruled out and the second axion cannot obey the scale independent mass formula. In an appendix we quantitatively justify the often held assumption that temperature corrections to the zero temperature QCD axion mass may be ignored for temperatures T {approx}&lt; {Lambda}{sub QCD}.
Date: December 15, 2005
Creator: Kain, Ben
Partner: UNT Libraries Government Documents Department

Multiple Peaks in the Angular Power Spectrum of the CosmicMicrowave Background: Significance and Consequences for Cosmology

Description: Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at {ell} {approx} 210, 540, 840 and {ell} {approx} 420, 750, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: {Omega}{sub tot} = 1.02{sub -0.05}{sup +0.06} vs. 1.04 {+-} 0.05, {Omega}{sub b}h{sup 2} = 0.022{sub -0.003}{sup +0.004} vs. 0.019{sub -0.004}{sup +0.005}, and n{sub s} = 0.96{sub -0.09}{sup +0.10} vs. 0.90 {+-} 0.08. The deviation in primordial spectral index n{sub s} is a consequence of the strong correlation with the optical depth.
Date: May 17, 2001
Creator: de Bernardis, P.; Ade, P.A.R.; Bock, J.J.; Bond, J.R.; Borrill,J.; Boscaleri, A. et al.
Partner: UNT Libraries Government Documents Department

Cross-correlations of the Lyman-alpha forest with weak lensing convergence I: Analytical Estimates of S/N and Implications for Neutrino Mass and Dark Energy

Description: We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line-of-sight. While the cross-correlation between these two measurements is small for a single line-of-sight, upcoming large surveys should enable its detection. This paper presents analytical estimates for the signal to noise (S/N) for measurements of the cross-correlation between the flux decrement and the convergence, {delta}F{kappa}, and for measurements of the cross-correlation between the variance in flux decrement and the convergence, &lt;({delta}F){sup 2}{kappa}&gt;. For the ongoing BOSS (SDSS III) and Planck surveys, we estimate an S/N of 30 and 9.6 for these two correlations. For the proposed BigBOSS and ACTPOL surveys, we estimate an S/N of 130 and 50 respectively. Since &lt;({delta}F){sup 2}{kappa}&gt; {proportional_to} {delta}{sub s}{sup 4}, the amplitude of these cross-correlations can potentially be used to measure the amplitude of {delta}{sub 8} at z {approx} 2 to 2.5% with BOSS and Planck and even better with future data sets. These measurements have the potential to test alternative theories for dark energy and to constrain the mass of the neutrino. The large potential signal estimated in our analytical calculations motivate tests with non-linear hydrodynamical simulations and analyses of upcoming data sets.
Date: October 1, 2009
Creator: Vallinotto, Alberto; Viel, Matteo; Das, Sudeep & Spergel, David N.
Partner: UNT Libraries Government Documents Department

A Measurement of the Temperature of the Cosmic MicrowaveBackground at a Frequency of 7.5 GHz

Description: We have measured the intensity of the cosmic microwave background (CMB) at a frequency of 7.5 GHz (wavelength 4.0 cm) using a ground-based, total power radiometer calibrated at the horn aperture by an external cryogenic reference target. The radiometer measured the difference in antenna temperature between the reference target and the zenith sky from a dry, high-altitude site. Subtraction of foreground signals (primarily atmospheric and galactic emission) measured with the same instrument leaves the CMB as the residual. The radiometer measured the atmospheric antenna temperature by correlating the signal change with the airmass in the beam during tip scans. The small galactic signal was subtracted based on extrapolation from lower frequencies, and was checked by differential drift scans. The limiting uncertainty in the CMB measurement was the effect of ground radiation in the antenna sidelobes during atmospheric measurements. The thermodynamic temperature of the CMB at 7.5 GHz is 2.59 {+-} 0.07 K (68% confidence level).
Date: June 1, 1989
Creator: Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Smoot,George F. & Witebsky, C.
Partner: UNT Libraries Government Documents Department