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Constraining dark energy fluctuations with supernova correlations
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). (CoPS)
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). (CoPS)
2010 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, Vol. 10, 018- p.Article in journal (Refereed) Published
Abstract [en]

We investigate constraints on dark energy fluctuations using type Ia supernovae. If dark energy is not in the form of a cosmological constant, that is if the equation of state is not equal to -1, we expect not only temporal, but also spatial variations in the energy density. Such fluctuations would cause local variations in the universal expansion rate and directional dependences in the redshift-distance relation. We present a scheme for relating a power spectrum of dark energy fluctuations to an angular covariance function of standard candle magnitude fluctuations. The predictions for a phenomenological model of dark energy fluctuations are compared to observational data in the form of the measured angular covariance of Hubble diagram magnitude residuals for type Ia supernovae in the Union2 compilation. The observational result is consistent with zero dark energy fluctuations. However, due to the limitations in statistics, current data still allow for quite general dark energy fluctuations as long as they are in the linear regime.

Place, publisher, year, edition, pages
2010. Vol. 10, 018- p.
Keyword [en]
cosmology, dark energy, supernovae
National Category
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-43080DOI: 10.1088/1475-7516/2010/10/018ISI: 000283577600017OAI: oai:DiVA.org:su-43080DiVA: diva2:353533
Available from: 2010-09-27 Created: 2010-09-27 Last updated: 2011-12-12Bibliographically approved
In thesis
1. Inhomogeneous cosmologies with clustered dark energy or a local matter void
Open this publication in new window or tab >>Inhomogeneous cosmologies with clustered dark energy or a local matter void
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the standard model of cosmology, the universe is currently dominated by dark energy in the form of the cosmological constant that drives the expansion to accelerate. While the cosmological constant hypothesis is consistent with all current data, models with dynamical behaviour of dark energy are still allowed by observations. Uncertainty also remains over whether the underlying assumption of a homogeneous and isotropic universe is valid, or if large-scale inhomogeneities in the matter distribution can be the cause of the apparent late-time acceleration.This thesis investigates inhomogeneous cosmological models in which dark energy clusters or where we live inside an underdense region in a matter-dominated universe. In both of these scenarios, we expect directional dependences in the redshift-luminosity distance relation of type Ia supernovae. Dynamical models of dark energy predict spatial variations in the dark energy density. Searches for angular correlated fluctuations in the supernova peak magnitudes, as expected if dark energy clusters, yield results consistent with no dark energy fluctuations. However, the current observational limits on the amount of correlation still allow for quite general dark energy clustering occurring in the linear regime. Inhomogeneous models where we live inside a large, local void in the matter density can possibly explain the apparent acceleration without invoking dark energy. This scenario is confronted with current cosmological distance measurements to put constraints on the size and depth of the void, as well as on our position within it. The model is found to explain the observations only if the void size is of the order of the visible universe and the observer is located very close to the center, in violation of the Copernican principle.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2010. 76 p.
Keyword
dark energy, type Ia supernova, inhomogeneous
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-43100 (URN)978-91-7447-145-8 (ISBN)
Public defence
2010-11-05, FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted.Available from: 2010-10-14 Created: 2010-09-28 Last updated: 2010-10-18Bibliographically approved

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Blomqvist, MichaelEnander, JonasMörtsell, Edvard
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