Structure in the COBE differential microwave radiometer first-year maps

Smoot, G. F.; Bennett, C. L.; Kogut, A.; Wright, E. L.; Aymon, J.; Boggess, N. W.; Cheng, E. S.; Amici, Giovanni De; Gulkis, S.; Hauser, M. G.; Hinshaw, G.; Jackson, P. D.; Janssen, M. A.; Kaita, Ed; Kelsall, T.; Keegstra, P.; Lineweaver, Charles H.; Loewenstein, K.; Lubin, P. M.; Mather, John C.; Meyer, S. S.; Moseley, S. H.; Murdock, T. L.; Rokke, L.; Silverberg, R. F.; Tenorio, Luis; Weiß, R.; Wilkinson, D. T.

doi:10.1086/186504

Cited by 2,379 publications

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“…Temperature maps of the cosmic microwave background [1] quite conclusively show that the universe was homogeneous on super-horizon scales already during its early stages. If the age of the universe at that time had been infinite or very large, this observation would not pose any particular problem; the universe would have had plenty of time to become homogeneous and isotropic by recombination.…”

Section: Introductionmentioning

confidence: 90%

“…1 The earliest possible moment at which this is meaningful is the time at which the physical momentum of a mode equals the cutoff of the theory. Again, one could simply postulate that trans-Planckian effects placed the state of the perturbations in the Bunch-Davies vacuum (or any other similar state), or that the latter is the natural state for the perturbations to be born into.…”

Section: Introductionmentioning

confidence: 99%

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Why should primordial perturbations be in a vacuum state?

Armendariz-Picon¹

2007

J. Cosmol. Astropart. Phys.

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In order to calculate the power spectrum generated during a stage of inflation, we have to specify the quantum state of the inflaton perturbations, which is conventionally assumed to be the BunchDavies vacuum. We argue that this choice is justified only if the interactions of cosmological perturbations are strong enough to drive excited states toward the vacuum. We quantify this efficiency by calculating the decay probabilities of excited states to leading order in the slowroll expansion in canonical single-field inflationary models. These probabilities are suppressed by a slow-roll parameter and the squared Planck mass, and enhanced by ultraviolet and infrared cut-offs.For natural choices of these scales decays are unlikely, and, hence, the choice of the Bunch-Davies vacuum as the state of the primordial perturbations does not appear to be warranted.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Why should primordial perturbations be in a vacuum state?

Armendariz-Picon¹

2007

J. Cosmol. Astropart. Phys.

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“…Reconciling this result with the standard inflationary cosmology prediction of a spatially flat universe (Guth, 1981) required a new energy component with density parameter 1 − Ω m . Open-universe inflation models were also considered, but explaining the observed homogeneity of the CMB (Smoot et al, 1992) in such models required speculative appeals to quantum gravity effects (e.g., Bucher et al 1995) rather than the semi-classical explanation of traditional inflation.…”

Section: Historymentioning

confidence: 99%

Observational probes of cosmic acceleration

et al. 2013

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The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H 0 . We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.

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“…As first observed in 1992 by the COBE satellite [8] and afterwards by several other ground-and balloon-based experiments, the nearly perfect black body spectrum of the CMB has little temperature fluctuations of the order δT /T ∼ 18µK 2.725K ∼ 10 −5 . The angular size of these fluctuations encodes the density and velocity fluctuations at the surface of last scattering, with redshift z ≃ 1100.…”

Section: Introduction and Overviewmentioning

confidence: 67%

Inflation and quintessence: theoretical approach of cosmological reconstruction

Neupane

Scherer

2008

J. Cosmol. Astropart. Phys.

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In the first part of this paper, we outline the construction of an inflationary cosmology in the framework where inflation is described by a universally evolving scalar field φ with potential V (φ). By considering a generic situation that inflaton attains a nearly constant velocity, during inflation, m −1 P |dφ/dN | ≡ α + β exp(βN ) (where N ≡ ln a is the e-folding time), we reconstruct a scalar potential and find the conditions that have to satisfied by the (reconstructed) potential to be consistent with the WMAP inflationary data. The consistency of our model with WMAP result (such as n s = 0.951 +0.015 −0.019 and r < 0.3) would require 0.16 < α < 0.26 and β < 0. The running of spectral index, α ≡ dn s /d ln k, is found to be small for a wide range of α.In the second part of this paper, we introduce a novel approach of constructing dark energy within the context of the standard scalar-tensor theory. The assumption that a scalar field might roll with a nearly constant velocity, during inflation, can also be applied to quintessence or dark energy models. For the minimally coupled quintessence, α Q ≡ dA(Q)/d(κQ) = 0 (where A(Q) is the standard matter-quintessence coupling), the dark energy equation of state in the range −1 ≤ w DE < −0.82 can be obtained for 0 ≤ α < 0.63. For α < 0.1, the model allows for only modest evolution of dark energy density with redshift. We also show, under certain conditions, that the α Q > 0 solution decreases the dark energy equation of state w Q with decreasing redshift as compared to the α Q = 0 solution. This effect can be opposite in the α Q < 0 case. The effect of the matterquintessence coupling can be significant only if |α Q | 0.1, while a small coupling |α Q | < 0.1 will have almost no effect on cosmological parameters, including Ω Q , w Q and H(z). The best fit value of α Q in our model is found to be α Q ≃ 0.06, but it may contain significant numerical errors, viz α Q = 0.06 ± 0.35, which thereby implies the consistency of our model with general relativity (for which α Q = 0) at 1σ level.

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Structure in the COBE differential microwave radiometer first-year maps

Cited by 2,379 publications

References 0 publications

Why should primordial perturbations be in a vacuum state?

Why should primordial perturbations be in a vacuum state?

Observational probes of cosmic acceleration

Inflation and quintessence: theoretical approach of cosmological reconstruction

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