Supernova tests of the timescape cosmology

Smale, Peter R.; Wiltshire, David L.

doi:10.1111/j.1365-2966.2010.18142.x

Cited by 37 publications

(75 citation statements)

References 77 publications

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“…It has been argued that confronting the backreaction models using the cosmological observational data may require more sophisticated approaches [36][37][38][39] than what one generally does in case of dark energy models. However, in the present case we have mapped the scalar field originating due to differential scale factors of the local domains into a large global domain such that it can fit the Friedmannian cosmology at the relevant large scales.…”

Section: Discussionmentioning

confidence: 99%

Future evolution in a backreaction model and the analogous scalar field cosmology

Ali

Majumdar

2017

J. Cosmol. Astropart. Phys.

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Abstract. We investigate the future evolution of the universe using the Buchert framework for averaged backreaction in the context of a two-domain partition of the universe. We show that this approach allows for the possibility of the global acceleration vanishing at a finite future time, provided that none of the subdomains accelerate individually. The model at large scales is analogously described in terms of a homogeneous scalar field emerging with a potential that is fixed and free from phenomenological parametrization. The dynamics of this scalar field is explored in the analogous FLRW cosmology. We use observational data from Type Ia Supernovae, Baryon Acoustic Oscillations, and Cosmic Microwave Background to constrain the parameters of the model for a viable cosmology, providing the corresponding likelihood contours.

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Section: Discussionmentioning

confidence: 99%

Future evolution in a backreaction model and the analogous scalar field cosmology

Ali

Majumdar

2017

J. Cosmol. Astropart. Phys.

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“…the discussion in Afshordi 2012). The SNIa flux-redshift data may at least partially be explained with an inhomogeneous universe (Wiltshire 2009;Smale & Wiltshire 2011;Marra, Pääkk€ onen & Valkenburg 2012) rather than with DE, whereby systematics in SNIa light curve fitting remain an issue (Smale & Wiltshire 2011). Bull & Clifton (2012) find that the 'appearance of acceleration in observations made over large scales does not necessarily imply or require the expansion of space to be accelerating, nor does it require local observables to indicate acceleration'.…”

Section: Curvature and Homogeneity (1980)mentioning

confidence: 99%

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology

Kroupa¹

2012

Publ. – Astron. Soc. Aust

232

272

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Abstract:The current standard model of cosmology (SMoC) requires The Dual Dwarf Galaxy Theorem to be true according to which two types of dwarf galaxies must exist: primordial dark-matter (DM) dominated (type A) dwarf galaxies, and tidal-dwarf and ram-pressure-dwarf (type B) galaxies void of DM. Type A dwarfs surround the host approximately spherically, while type B dwarfs are typically correlated in phasespace. Type B dwarfs must exist in any cosmological theory in which galaxies interact. Only one type of dwarf galaxy is observed to exist on the baryonic Tully-Fisher plot and in the radius-mass plane. The Milky Way satellite system forms a vast phase-space-correlated structure that includes globular clusters and stellar and gaseous streams. Other galaxies also have phase-space correlated satellite systems. Therefore, The Dual Dwarf Galaxy Theorem is falsified by observation and dynamically relevant cold or warm DM cannot exist. It is shown that the SMoC is incompatible with a large set of other extragalactic observations. Other theoretical solutions to cosmological observations exist. In particular, alone the empirical mass-discrepancyacceleration correlation constitutes convincing evidence that galactic-scale dynamics must be Milgromian. Major problems with inflationary big bang cosmologies remain unresolved.

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“…Finally, we note that several authors argued that supernova samples reduced with the SALT-II light-curve fitter from Guy et al (2007) are systematically biased towards the standard cosmological model and tend to disfavour alternative cosmologies (Hicken et al 2009;Kessler et al 2009;Smale & Wiltshire 2011). The Union2.1 compilation was reduced with the SALT-II fitter, and hence this potential penalty would also affect the goodness-of-fit of LTB models.…”

Section: Supernovaementioning

confidence: 99%

Probing spatial homogeneity with LTB models: a detailed discussion

Redlich

Bolejko

Meyer

et al. 2014

A&A

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Do current observational data confirm the assumptions of the cosmological principle, or is there statistical evidence for deviations from spatial homogeneity on large scales? To address these questions, we developed a flexible framework based on spherically symmetric, but radially inhomogeneous Lemaître-Tolman-Bondi (LTB) models with synchronous Big Bang. We expanded the (local) matter density profile in terms of flexible interpolation schemes and orthonormal polynomials. A Monte Carlo technique in combination with recent observational data was used to systematically vary the shape of these profiles. In the first part of this article, we reconsider giant LTB voids without dark energy to investigate whether extremely fine-tuned mass profiles can reconcile these models with current data. While the local Hubble rate and supernovae can easily be fitted without dark energy, however, model-independent constraints from the Planck 2013 data require an unrealistically low local Hubble rate, which is strongly inconsistent with the observed value; this result agrees well with previous studies. In the second part, we explain why it seems natural to extend our framework by a non-zero cosmological constant, which then allows us to perform general tests of the cosmological principle. Moreover, these extended models facilitate explorating whether fluctuations in the local matter density profile might potentially alleviate the tension between local and global measurements of the Hubble rate, as derived from Cepheid-calibrated type Ia supernovae and CMB experiments, respectively. We show that current data provide no evidence for deviations from spatial homogeneity on large scales. More accurate constraints are required to ultimately confirm the validity of the cosmological principle, however.

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Supernova tests of the timescape cosmology

Cited by 37 publications

References 77 publications

Future evolution in a backreaction model and the analogous scalar field cosmology

Future evolution in a backreaction model and the analogous scalar field cosmology

The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology

Probing spatial homogeneity with LTB models: a detailed discussion

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