Rohrleitungen aus Nichteisenmetallen

Helbig, Ulf

doi:10.1007/978-3-642-39782-0_7

Cited by 2 publications

(4 citation statements)

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“…First, this could be the averaging mentioned by Weinberg (1976), skewed to slightly lower values because of selection effects. Second, the physical model on which the ZKDR distance is based is wrong, but in our Universe the m-z relation is similar to that in a highη ZKDR universe (Peel et al 2014;Helbig 2015b) (see Sect. 27).…”

Section: Classical Cosmology: Generalmentioning

confidence: 86%

“…Indeed, the scatter does increase with redshift, but so do the observational uncertainties. Since their quotient is independent of redshift, this indicates that each line of sight indicates η ≈ 1, in other words that all lines of sight fairly sample the mass distribution of the Universe 32 (Helbig 2015b). Note that Holz & Linder (2005) find a scatter (calculated theoretically) approximated by a Gaussian with standard deviation σ eff = 0.088z (in flux) or σ eff,m = 0.093z (in magnitudes).…”

Section: Relationmentioning

confidence: 88%

“…Note that Holz & Linder (2005) find a scatter (calculated theoretically) approximated by a Gaussian with standard deviation σ eff = 0.088z (in flux) or σ eff,m = 0.093z (in magnitudes). However, as discussed by Helbig (2015b), the observed increase in scatter with redshift seems primarily due to observational uncertainties in addition to the theoretically calculated scatter sometimes incorporated into those uncertainties.…”

Section: Relationmentioning

confidence: 93%

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Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology: a review

Helbig¹

2020

TheOJA

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The Universe is not completely homogeneous. Even if it is sufficiently so on large scales, it is very inhomogeneous at small scales, and this has an effect on light propagation, so that the distance as a function of redshift, which in many cases is defined via light propagation, can differ from the homogeneous case. Simple models can take this into account. I review the history of this idea, its generalization to a wide variety of cosmological models, analytic solutions of simple models, comparison of such solutions with exact solutions and numerical simulations, applications, simpler analytic approximations to the distance equations, and (for all of these aspects) the related concept of a 'Swiss-cheese' universe.

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Section: Classical Cosmology: Generalmentioning

confidence: 86%

Section: Relationmentioning

confidence: 88%

Section: Relationmentioning

confidence: 93%

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Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology: a review

Helbig¹

2020

TheOJA

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“…In the present work, we also neglect the effects of gravitational lensing on SN Ia analyses. Though the dispersion induced by lensing may be non-negligible in forthcoming analyses (Zentner & Bhattacharya 2009), lensing does not shift the average brightness (setting aside observational selection effects for the moment) and is unlikely to bias cosmological results (Helbig 2015). We defer a more complex analysis including lensing to future work.…”

Section: Generating Mock Data Setsmentioning

confidence: 97%

INCORPORATING ASTROPHYSICAL SYSTEMATICS INTO A GENERALIZED LIKELIHOOD FOR COSMOLOGY WITH TYPE Ia SUPERNOVAE

Ponder

Wood‐Vasey

Zentner

2016

ApJ

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Traditional cosmological inference using Type Ia supernovae (SNeIa) have used stretch-and colorcorrected fits of SN Ia light curves and assumed a resulting fiducial mean and symmetric intrinsic dispersion for the resulting relative luminosity. As systematics become the main contributors to the error budget, it has become imperative to expand supernova cosmology analyses to include a more general likelihood to model systematics to remove biases with losses in precision. To illustrate an example likelihood analysis, we use a simple model of two populations with a relative luminosity shift, independent intrinsic dispersions, and linear redshift evolution of the relative fraction of each population. Treating observationally viable two-population mock data using a one-population model results in an inferred dark energy equation of state parameter w that is biased by roughly 2 times its statistical error for a sample of N 2500 SNeIa. Modeling the two-population data with a twopopulation model removes this bias at a cost of an approximately ∼ 20% increase in the statistical constraint on w. These significant biases can be realized even if the support for two underlying SNeIa populations, in the form of model selection criteria, is inconclusive. With the current observationallyestimated difference in the two proposed populations, a sample of N 10,000 SNeIa is necessary to yield conclusive evidence of two populations.

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Rohrleitungen aus Nichteisenmetallen

Cited by 2 publications

References 1 publication

Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology: a review

Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology: a review

INCORPORATING ASTROPHYSICAL SYSTEMATICS INTO A GENERALIZED LIKELIHOOD FOR COSMOLOGY WITH TYPE Ia SUPERNOVAE

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